1. Polarography is an electroanalytical technique that uses a dropping mercury electrode and measures the current as a function of the applied voltage to determine analyte concentration and properties.
2. Key aspects of polarography include using a polarized indicator electrode such as mercury and an unpolarized reference electrode, operating under diffusion-controlled conditions without stirring, and renewing the mercury surface between measurements.
3. The diffusion current is directly proportional to analyte concentration, allowing quantitative analysis via calibration curves or standard addition. Oxygen interference is eliminated by bubbling nitrogen through the solution.
Coulometry is an electrochemical method that measures the current needed to completely oxidize or reduce an analyte. There are two forms: controlled potential and controlled current. Controlled potential coulometry applies a constant potential to ensure 100% current efficiency and quantitative reaction of the analyte without interfering species. The decreasing current over time corresponds to decreasing analyte concentration. Controlled current coulometry passes a constant current, allowing more rapid analysis since current does not decrease over time. The total charge simply equals current multiplied by time. Coulometry provides precise, sensitive, and selective analysis of inorganic and organic compounds and can be adapted to automatic titration methods.
This document provides an overview of interfacial electrochemistry. It discusses how interfaces form boundaries between different phases of matter and influence interactions with the environment due to changed atomic structures. Most electrochemical events occur at interfaces, making interfacial electrochemistry important. When two dissimilar materials contact, charge separation occurs across the interface, creating an interfacial potential difference. The document also describes models of the electrical double layer that forms at electrode-electrolyte interfaces, such as the Helmholtz-Perrin and Gouy-Chapman models.
Chronopotentiometry is an electrochemical technique that applies a constant current between electrodes and measures the potential over time. It can be used to investigate electroporation of bilayer lipid membranes. When a constant current is applied, the potential gradually changes as oxidation and reduction reactions occur at the electrodes. Ultimately, the concentration of one species is depleted at the electrode surface, causing a rapid change in potential. Chronopotentiometry provides simple information about membrane pores but is not well-suited for studying capacitive currents.
Polarography is an electroanalytical technique invented by Jaroslav Heyrovsky in 1922. It involves using a dropping mercury electrode and measuring the current in the solution at different applied potentials to generate a current-voltage curve called a polarogram. There are four main types of current measured: residual, migration, diffusion, and limiting current. The construction includes a dropping mercury electrode, supporting electrolyte, mercury reservoir, and capillary tube. Polarography can be used for qualitative and quantitative analysis of samples without separation and allows analysis of small amounts of inorganic and organic substances.
This document summarizes voltammetry, an electrochemical method that uses a three-electrode system to obtain information about analytes. A voltage ramp is applied to the working electrode to reduce ions, while current is measured. Common types of voltammetry include cyclic, square wave, differential pulse, and stripping voltammetry. The working electrode potential is varied over time, while the reference electrode potential remains constant. Voltammetry can be used to determine metal ion concentrations, for wastewater analysis, and in various other applications due to its low detection limits and ability to handle high salt concentrations.
Electrogravimetry is a method used to separate and quantify ions of a substance, usually a metal, through electrolysis. The analyte solution is electrolyzed, causing the analyte to deposit on the cathode. The cathode is weighed before and after the experiment, and the mass difference is used to calculate the amount of analyte originally present. There are two types of electrogravimetry - constant current electrolysis, where the current is kept constant, and constant potential electrolysis, where the potential is kept constant. In both cases, the deposited analyte on the cathode is measured through changes in mass to determine the concentration in the original solution.
Electrogravimetric analysis involves the quantitative deposition of an analyte onto an electrode through electrolysis. There are two main types: constant current electrolysis, where the current is kept constant and the potential varies, and controlled potential electrolysis, where the potential is kept constant to selectively deposit analytes. Electrogravimetric analysis can be used for quantitative analysis, separation, preconcentration of analytes, and electrosynthesis.
Voltammetry refers to a category of electroanalytical techniques used in analytical chemistry where information about an analyte is obtained by measuring the current as the potential is varied. There are several types of voltammetry including linear sweep voltammetry, cyclic voltammetry, and differential pulse voltammetry. Voltammetry is used to determine concentrations of analytes in a variety of samples including environmental, clinical, food, and pharmaceutical samples. It provides selective, rapid, and sensitive analysis with detection limits in the parts-per-billion or parts-per-trillion range depending on the technique and analyte.
Coulometry is an electrochemical method that measures the current needed to completely oxidize or reduce an analyte. There are two forms: controlled potential and controlled current. Controlled potential coulometry applies a constant potential to ensure 100% current efficiency and quantitative reaction of the analyte without interfering species. The decreasing current over time corresponds to decreasing analyte concentration. Controlled current coulometry passes a constant current, allowing more rapid analysis since current does not decrease over time. The total charge simply equals current multiplied by time. Coulometry provides precise, sensitive, and selective analysis of inorganic and organic compounds and can be adapted to automatic titration methods.
This document provides an overview of interfacial electrochemistry. It discusses how interfaces form boundaries between different phases of matter and influence interactions with the environment due to changed atomic structures. Most electrochemical events occur at interfaces, making interfacial electrochemistry important. When two dissimilar materials contact, charge separation occurs across the interface, creating an interfacial potential difference. The document also describes models of the electrical double layer that forms at electrode-electrolyte interfaces, such as the Helmholtz-Perrin and Gouy-Chapman models.
Chronopotentiometry is an electrochemical technique that applies a constant current between electrodes and measures the potential over time. It can be used to investigate electroporation of bilayer lipid membranes. When a constant current is applied, the potential gradually changes as oxidation and reduction reactions occur at the electrodes. Ultimately, the concentration of one species is depleted at the electrode surface, causing a rapid change in potential. Chronopotentiometry provides simple information about membrane pores but is not well-suited for studying capacitive currents.
Polarography is an electroanalytical technique invented by Jaroslav Heyrovsky in 1922. It involves using a dropping mercury electrode and measuring the current in the solution at different applied potentials to generate a current-voltage curve called a polarogram. There are four main types of current measured: residual, migration, diffusion, and limiting current. The construction includes a dropping mercury electrode, supporting electrolyte, mercury reservoir, and capillary tube. Polarography can be used for qualitative and quantitative analysis of samples without separation and allows analysis of small amounts of inorganic and organic substances.
This document summarizes voltammetry, an electrochemical method that uses a three-electrode system to obtain information about analytes. A voltage ramp is applied to the working electrode to reduce ions, while current is measured. Common types of voltammetry include cyclic, square wave, differential pulse, and stripping voltammetry. The working electrode potential is varied over time, while the reference electrode potential remains constant. Voltammetry can be used to determine metal ion concentrations, for wastewater analysis, and in various other applications due to its low detection limits and ability to handle high salt concentrations.
Electrogravimetry is a method used to separate and quantify ions of a substance, usually a metal, through electrolysis. The analyte solution is electrolyzed, causing the analyte to deposit on the cathode. The cathode is weighed before and after the experiment, and the mass difference is used to calculate the amount of analyte originally present. There are two types of electrogravimetry - constant current electrolysis, where the current is kept constant, and constant potential electrolysis, where the potential is kept constant. In both cases, the deposited analyte on the cathode is measured through changes in mass to determine the concentration in the original solution.
Electrogravimetric analysis involves the quantitative deposition of an analyte onto an electrode through electrolysis. There are two main types: constant current electrolysis, where the current is kept constant and the potential varies, and controlled potential electrolysis, where the potential is kept constant to selectively deposit analytes. Electrogravimetric analysis can be used for quantitative analysis, separation, preconcentration of analytes, and electrosynthesis.
Voltammetry refers to a category of electroanalytical techniques used in analytical chemistry where information about an analyte is obtained by measuring the current as the potential is varied. There are several types of voltammetry including linear sweep voltammetry, cyclic voltammetry, and differential pulse voltammetry. Voltammetry is used to determine concentrations of analytes in a variety of samples including environmental, clinical, food, and pharmaceutical samples. It provides selective, rapid, and sensitive analysis with detection limits in the parts-per-billion or parts-per-trillion range depending on the technique and analyte.
This document discusses cyclic voltammetry, which is a type of potentiodynamic electrochemical measurement where the current in an electrochemical cell is measured while the cell's potential is varied linearly with time. It describes the components of a voltammetry system, including the working, reference, and counter electrodes, as well as the supporting electrolyte. It also explains the triangular potential waveform used and defines terms like peak current and peak potential. Examples of using cyclic voltammetry to study the redox reaction of hexacyanoferrate ions and biological redox systems like cytochromes are provided.
This document discusses applications of cyclic voltammetry (CV). CV is an electrochemical technique useful for studying electrode reactions. It involves applying a continuous, cyclic potential to a working electrode in a cell containing three electrodes. The document outlines the principle, working, and applications of CV, including quantitative analysis, studying chemical reactivity and redox processes, determining thermodynamic properties, kinetics, and more. Examples are given of using CV to characterize modified electrodes and study interactions like of anticancer drugs with DNA.
This document discusses microwave spectroscopy and its application to determining properties of gas phase molecules. It can be summarized as follows:
1) Microwave spectroscopy utilizes photons in the microwave range to cause rotational energy level transitions in gas molecules. It is applicable to molecules with a permanent dipole moment in the gas phase.
2) The rotational energy levels of diatomic molecules can be modeled using a rigid rotor approximation. This allows derivation of an expression for rotational energy levels in terms of the rotational constant B, which depends on the molecule's moment of inertia.
3) Measurement of transition frequencies between rotational energy levels allows determination of the rotational constant B. This can then be used to calculate bond distances in diatomic molecules.
Voltammetry is a technique where a time-dependent potential is applied to an electrochemical cell and the current is measured as a function of the applied potential. This results in a voltammogram which provides qualitative and quantitative information about redox reactions. The earliest technique was polarography developed in the 1920s. Modern voltammetry uses a three-electrode system with various excitation signals applied. Common techniques include normal pulse polarography, differential pulse polarography, staircase polarography and square wave polarography which have better sensitivity than normal polarography. The shape of the voltammetric wave depends on factors like the reversibility of the redox reaction. The diffusion current occurs at very negative potentials where the reaction rate is controlled by diffusion
Voltammetry involves applying a potential to a working electrode and measuring the resulting current. It can characterize redox reactions through parameters like peak potentials and currents in cyclic voltammetry. Cyclic voltammetry cycles the potential of a working electrode versus a reference electrode and measures the current. It is used to study redox processes and obtain information about reaction kinetics and mechanisms. The peak separation and shapes of cyclic voltammograms provide information about whether redox processes are reversible or irreversible.
Photoelectron spectroscopy
- a single photon in/ electron out process
• X-ray Photoelectron Spectroscopy (XPS)
- using soft x-ray (200-2000 eV) radiation to
examine core-levels.
• Ultraviolet Photoelectron Spectroscopy (UPS)
- using vacuum UV (10-45 eV) radiation to
examine valence levels.
Coulometry is an electroanalytical technique where the amount of electricity (in coulombs) required to complete an electrochemical reaction is measured. There are two main types - potentiostatic coulometry, where the potential is held constant, and coulometric titration with a constant current. The quantity of electricity is directly proportional to the amount of analyte and can be used to determine concentrations. Coulometry has applications in inorganic analysis, analysis of radioactive materials, microanalysis, and determination of organic compounds.
This document discusses electrogravimetry, which is the quantitative analysis of substances by electrolysis. It defines key terms used in electrogravimetry like cathode, anode, current density, and overpotential. It explains Faraday's laws of electrolysis and how they relate to the amount of material deposited. It also describes how controlling variables like cathode potential can be used to selectively deposit metals and separate them from each other.
Dc,pulse,ac and square wave polarographic techniques newBiji Saro
DC, pulse, AC, and square wave polarographic techniques are electroanalytical methods used to determine the concentration and nature of electroactive species in solutions. DC polarography applies a continuously increasing voltage to generate a sigmoidal current-voltage curve. Pulse polarography applies voltage pulses to eliminate non-faradaic currents and improve detection limits. AC polarography superimposes an AC potential on DC to measure the AC current component. Square wave polarography uses large amplitude square waves to sample current twice per cycle and plot the net current versus voltage. These techniques enable sensitive quantitative analysis down to micromolar and even nanomolar concentration levels.
This document provides an overview of coulometry, which is an electroanalytical technique used for quantitative analysis. There are two forms of coulometry: controlled-potential coulometry and controlled-current coulometry. Both techniques involve completely oxidizing or reducing an analyte and measuring the total charge passed to determine the amount of analyte. Controlled-potential coulometry applies a constant potential while controlled-current coulometry applies a constant current. Factors like electrolysis time, electrode area, and stirring rate affect the analysis. Coulometry is used to quantify both inorganic and organic analytes.
Nuclear Quadrupole Resonance Spectroscopy (NQR) is a chemical analysis technique that detects nuclear energy level transitions in the absence of a magnetic field through the absorption of radio frequency radiation. NQR is applicable to solids due to the quadrupole moment averaging to zero in liquids and gases. The interaction between a nucleus's quadrupole moment and the electric field gradient of its surroundings results in quantized energy levels. Transitions between these levels are detected as NQR spectra and provide information about electronic structure, hybridization, and charge distribution. NQR finds applications in studying charge transfer complexes, detecting crystal imperfections, and locating land mines.
Coulometry is an electroanalytical technique that measures the quantity of electricity required for a chemical reaction. There are two main types - controlled potential coulometry (potentiostatic coulometry) and controlled current coulometry (galvanostatic coulometry). Controlled potential coulometry involves holding the working electrode at a constant potential to allow exhaustive electrolysis of the analyte without interfering reactions. The quantity of electricity passed is proportional to the analyte concentration and is measured with an electronic integrator. Applications include determination of metal ions, microanalysis, and analysis of radioactive materials like uranium.
Resonance Raman spectroscopy is a technique that enhances Raman scattering intensity when the laser excitation wavelength matches an electronic transition in the molecule or material being examined. This resonance effect can increase Raman intensities by several orders of magnitude, allowing detection of low concentration compounds. The enhanced signals are selective for vibrational modes that change during electronic excitation according to Tsuboi's rule. This selectivity enables resonance Raman spectroscopy to identify specific functional groups within large biomolecules like proteins. Applications include analyzing heme groups in hemoglobin and metal-ligand vibrations in metal complexes.
This document discusses the principles and methods of voltammetry and polarography. Some key points:
- Voltammetry measures the current-potential curve during electrolysis using a small amount of sample. Polarography uses a dropping mercury electrode as the working electrode.
- In polarographic analysis, a polarized working electrode and depolarized reference electrode are used. No stirring is used. Only a small amount of analyte undergoes electrolysis.
- The limiting diffusion current is proportional to analyte concentration and can be used for quantitative analysis. The half-wave potential is used for qualitative analysis.
- Factors like temperature, supporting electrolyte composition, and mercury electrode potential affect the limiting diffusion current.
Coulometry and electrogravimetric analysis are analytical techniques that involve completely oxidizing or reducing an analyte through electrolysis. In coulometry, the quantity of electrical charge passed is measured and related to the amount of analyte present. In electrogravimetry, the analyte is converted electrolytically into a product that is weighed to determine the analyte amount. Both techniques are accurate and precise, but require ensuring all current passed results in analyte oxidation/reduction. Controlled-potential coulometry uses a constant potential, while controlled-current coulometry applies a constant current, each with their own experimental considerations to achieve complete analyte conversion.
Electrochemistry 1 the basic of the basicToru Hara
This document discusses key concepts in electrochemistry including the interface between electrode and electrolyte, thermodynamics and kinetics of electrode reactions, and overpotential. The interface contains an electric double layer consisting of an inner monomolecular layer, an outer diffuse region, and an intermediate layer. Overpotential arises from factors like activation energy needed for electrode reactions, concentration gradients that develop at the electrode surface, and resistance of the electrolyte. Overpotential is composed of ohmic drop, activation overpotential, and diffusion overpotential.
Shielding effect,effect of chemical exchange,hydrogen bondingSumeetJha12
This document summarizes key concepts related to NMR spectroscopy, including shielding effect, hydrogen bonding, and chemical exchange. It describes how the shielding effect causes some nuclei to experience less of an external magnetic field, requiring a higher frequency for resonance. Hydrogen bonding causes deshielding and higher chemical shift values as electron density around protons decreases. Chemical exchange refers to nuclei switching environments, which can lead to sharp, broad, or coupled peaks depending on the exchange rate relative to peak separation.
Polarography is an electroanalytical technique that uses a dropping mercury electrode to determine the concentration and nature of substances in a solution. It involves measuring the current between two electrodes - a polarized indicator electrode made of mercury, and a non-polarized reference electrode - as the voltage is gradually increased. The current readings form a polarogram curve that can identify substances based on their half-wave potential and determine concentrations from the limiting diffusion current. Polarography finds applications in fields like water quality testing, medicine, and electrochemistry.
Polarography uses a dropping mercury electrode (DME) to measure the current flowing through an electrochemical cell as a function of the applied potential. A polarogram plots this current versus potential and provides qualitative and quantitative information about species undergoing oxidation or reduction reactions. Jaroslav Heyrovsky invented the polarographic method in 1922 and won the Nobel Prize for his contributions to electroanalytical chemistry. All modern voltammetric methods originate from polarography. The DME provides advantages like a reproducible surface area and the ability to form amalgams with metal ions.
This document discusses cyclic voltammetry, which is a type of potentiodynamic electrochemical measurement where the current in an electrochemical cell is measured while the cell's potential is varied linearly with time. It describes the components of a voltammetry system, including the working, reference, and counter electrodes, as well as the supporting electrolyte. It also explains the triangular potential waveform used and defines terms like peak current and peak potential. Examples of using cyclic voltammetry to study the redox reaction of hexacyanoferrate ions and biological redox systems like cytochromes are provided.
This document discusses applications of cyclic voltammetry (CV). CV is an electrochemical technique useful for studying electrode reactions. It involves applying a continuous, cyclic potential to a working electrode in a cell containing three electrodes. The document outlines the principle, working, and applications of CV, including quantitative analysis, studying chemical reactivity and redox processes, determining thermodynamic properties, kinetics, and more. Examples are given of using CV to characterize modified electrodes and study interactions like of anticancer drugs with DNA.
This document discusses microwave spectroscopy and its application to determining properties of gas phase molecules. It can be summarized as follows:
1) Microwave spectroscopy utilizes photons in the microwave range to cause rotational energy level transitions in gas molecules. It is applicable to molecules with a permanent dipole moment in the gas phase.
2) The rotational energy levels of diatomic molecules can be modeled using a rigid rotor approximation. This allows derivation of an expression for rotational energy levels in terms of the rotational constant B, which depends on the molecule's moment of inertia.
3) Measurement of transition frequencies between rotational energy levels allows determination of the rotational constant B. This can then be used to calculate bond distances in diatomic molecules.
Voltammetry is a technique where a time-dependent potential is applied to an electrochemical cell and the current is measured as a function of the applied potential. This results in a voltammogram which provides qualitative and quantitative information about redox reactions. The earliest technique was polarography developed in the 1920s. Modern voltammetry uses a three-electrode system with various excitation signals applied. Common techniques include normal pulse polarography, differential pulse polarography, staircase polarography and square wave polarography which have better sensitivity than normal polarography. The shape of the voltammetric wave depends on factors like the reversibility of the redox reaction. The diffusion current occurs at very negative potentials where the reaction rate is controlled by diffusion
Voltammetry involves applying a potential to a working electrode and measuring the resulting current. It can characterize redox reactions through parameters like peak potentials and currents in cyclic voltammetry. Cyclic voltammetry cycles the potential of a working electrode versus a reference electrode and measures the current. It is used to study redox processes and obtain information about reaction kinetics and mechanisms. The peak separation and shapes of cyclic voltammograms provide information about whether redox processes are reversible or irreversible.
Photoelectron spectroscopy
- a single photon in/ electron out process
• X-ray Photoelectron Spectroscopy (XPS)
- using soft x-ray (200-2000 eV) radiation to
examine core-levels.
• Ultraviolet Photoelectron Spectroscopy (UPS)
- using vacuum UV (10-45 eV) radiation to
examine valence levels.
Coulometry is an electroanalytical technique where the amount of electricity (in coulombs) required to complete an electrochemical reaction is measured. There are two main types - potentiostatic coulometry, where the potential is held constant, and coulometric titration with a constant current. The quantity of electricity is directly proportional to the amount of analyte and can be used to determine concentrations. Coulometry has applications in inorganic analysis, analysis of radioactive materials, microanalysis, and determination of organic compounds.
This document discusses electrogravimetry, which is the quantitative analysis of substances by electrolysis. It defines key terms used in electrogravimetry like cathode, anode, current density, and overpotential. It explains Faraday's laws of electrolysis and how they relate to the amount of material deposited. It also describes how controlling variables like cathode potential can be used to selectively deposit metals and separate them from each other.
Dc,pulse,ac and square wave polarographic techniques newBiji Saro
DC, pulse, AC, and square wave polarographic techniques are electroanalytical methods used to determine the concentration and nature of electroactive species in solutions. DC polarography applies a continuously increasing voltage to generate a sigmoidal current-voltage curve. Pulse polarography applies voltage pulses to eliminate non-faradaic currents and improve detection limits. AC polarography superimposes an AC potential on DC to measure the AC current component. Square wave polarography uses large amplitude square waves to sample current twice per cycle and plot the net current versus voltage. These techniques enable sensitive quantitative analysis down to micromolar and even nanomolar concentration levels.
This document provides an overview of coulometry, which is an electroanalytical technique used for quantitative analysis. There are two forms of coulometry: controlled-potential coulometry and controlled-current coulometry. Both techniques involve completely oxidizing or reducing an analyte and measuring the total charge passed to determine the amount of analyte. Controlled-potential coulometry applies a constant potential while controlled-current coulometry applies a constant current. Factors like electrolysis time, electrode area, and stirring rate affect the analysis. Coulometry is used to quantify both inorganic and organic analytes.
Nuclear Quadrupole Resonance Spectroscopy (NQR) is a chemical analysis technique that detects nuclear energy level transitions in the absence of a magnetic field through the absorption of radio frequency radiation. NQR is applicable to solids due to the quadrupole moment averaging to zero in liquids and gases. The interaction between a nucleus's quadrupole moment and the electric field gradient of its surroundings results in quantized energy levels. Transitions between these levels are detected as NQR spectra and provide information about electronic structure, hybridization, and charge distribution. NQR finds applications in studying charge transfer complexes, detecting crystal imperfections, and locating land mines.
Coulometry is an electroanalytical technique that measures the quantity of electricity required for a chemical reaction. There are two main types - controlled potential coulometry (potentiostatic coulometry) and controlled current coulometry (galvanostatic coulometry). Controlled potential coulometry involves holding the working electrode at a constant potential to allow exhaustive electrolysis of the analyte without interfering reactions. The quantity of electricity passed is proportional to the analyte concentration and is measured with an electronic integrator. Applications include determination of metal ions, microanalysis, and analysis of radioactive materials like uranium.
Resonance Raman spectroscopy is a technique that enhances Raman scattering intensity when the laser excitation wavelength matches an electronic transition in the molecule or material being examined. This resonance effect can increase Raman intensities by several orders of magnitude, allowing detection of low concentration compounds. The enhanced signals are selective for vibrational modes that change during electronic excitation according to Tsuboi's rule. This selectivity enables resonance Raman spectroscopy to identify specific functional groups within large biomolecules like proteins. Applications include analyzing heme groups in hemoglobin and metal-ligand vibrations in metal complexes.
This document discusses the principles and methods of voltammetry and polarography. Some key points:
- Voltammetry measures the current-potential curve during electrolysis using a small amount of sample. Polarography uses a dropping mercury electrode as the working electrode.
- In polarographic analysis, a polarized working electrode and depolarized reference electrode are used. No stirring is used. Only a small amount of analyte undergoes electrolysis.
- The limiting diffusion current is proportional to analyte concentration and can be used for quantitative analysis. The half-wave potential is used for qualitative analysis.
- Factors like temperature, supporting electrolyte composition, and mercury electrode potential affect the limiting diffusion current.
Coulometry and electrogravimetric analysis are analytical techniques that involve completely oxidizing or reducing an analyte through electrolysis. In coulometry, the quantity of electrical charge passed is measured and related to the amount of analyte present. In electrogravimetry, the analyte is converted electrolytically into a product that is weighed to determine the analyte amount. Both techniques are accurate and precise, but require ensuring all current passed results in analyte oxidation/reduction. Controlled-potential coulometry uses a constant potential, while controlled-current coulometry applies a constant current, each with their own experimental considerations to achieve complete analyte conversion.
Electrochemistry 1 the basic of the basicToru Hara
This document discusses key concepts in electrochemistry including the interface between electrode and electrolyte, thermodynamics and kinetics of electrode reactions, and overpotential. The interface contains an electric double layer consisting of an inner monomolecular layer, an outer diffuse region, and an intermediate layer. Overpotential arises from factors like activation energy needed for electrode reactions, concentration gradients that develop at the electrode surface, and resistance of the electrolyte. Overpotential is composed of ohmic drop, activation overpotential, and diffusion overpotential.
Shielding effect,effect of chemical exchange,hydrogen bondingSumeetJha12
This document summarizes key concepts related to NMR spectroscopy, including shielding effect, hydrogen bonding, and chemical exchange. It describes how the shielding effect causes some nuclei to experience less of an external magnetic field, requiring a higher frequency for resonance. Hydrogen bonding causes deshielding and higher chemical shift values as electron density around protons decreases. Chemical exchange refers to nuclei switching environments, which can lead to sharp, broad, or coupled peaks depending on the exchange rate relative to peak separation.
Polarography is an electroanalytical technique that uses a dropping mercury electrode to determine the concentration and nature of substances in a solution. It involves measuring the current between two electrodes - a polarized indicator electrode made of mercury, and a non-polarized reference electrode - as the voltage is gradually increased. The current readings form a polarogram curve that can identify substances based on their half-wave potential and determine concentrations from the limiting diffusion current. Polarography finds applications in fields like water quality testing, medicine, and electrochemistry.
Polarography uses a dropping mercury electrode (DME) to measure the current flowing through an electrochemical cell as a function of the applied potential. A polarogram plots this current versus potential and provides qualitative and quantitative information about species undergoing oxidation or reduction reactions. Jaroslav Heyrovsky invented the polarographic method in 1922 and won the Nobel Prize for his contributions to electroanalytical chemistry. All modern voltammetric methods originate from polarography. The DME provides advantages like a reproducible surface area and the ability to form amalgams with metal ions.
This document discusses polarography, which is a technique for analyzing solutions using two electrodes - a dropping mercury working electrode and a reference electrode. It provides details on:
1. How polarography works by applying a voltage to induce a redox reaction and measuring the resulting current.
2. The components needed, including the dropping mercury electrode, reference electrode, and a supporting electrolyte.
3. How polarograms are generated by plotting current vs. applied voltage and the different regions that can be seen on a polarogram.
4. Factors that influence the diffusion current measured, such as concentration of the analyte, diffusion coefficient, and drop lifetime. Equations for calculating diffusion current are also presented.
Polarographic analysis is a voltammetry technique that uses a dropping mercury electrode (DME) or static mercury drop electrode (SMDE) to measure the current resulting from the electrolysis of electroactive species at controlled potentials. It involves applying a potential between a mercury working electrode and a reference electrode, like a saturated calomel electrode, while measuring the current. The current-voltage curve, or polarogram, reveals information about the species present in solution, including qualitative and quantitative analysis through measurements of diffusion current and half-wave potential. Polarography takes advantage of mercury's wide cathodic potential range and its ability to renew its surface between drops.
Polarography is an electroanalytical technique that measures the current between two electrodes in a solution. It can be used for both qualitative and quantitative analysis. The document discusses the principle, instrumentation, types of currents, and applications of polarography. Polarography involves applying a voltage to a dropping mercury electrode and reference electrode in an electrolyte solution and measuring the resulting current, which provides information about electroactive species in the solution.
Polarography is an electroanalytical technique that uses a dropping mercury electrode (DME) and measures the current between two electrodes when a gradually increasing voltage is applied. The current-voltage curve obtained is used to determine analyte concentration from the diffusion current and identify species from the characteristic half-wave potential. The Ilkovic equation relates diffusion current to analyte properties like concentration, number of electrons involved, and diffusion coefficient. Polarography finds applications in qualitative and quantitative analysis of metals, drugs, and organic compounds.
Polarography principle and instrumentationKIRANBARBATKAR
Jaroslav Heyrovsky invented polarography in 1922 and won the Nobel Prize for it in 1959. Polarography involves using a dropping mercury electrode (DME) and saturated calomel electrode (SCE) to study the electrical properties of solutions through electrolysis. As mercury drops from the DME into the solution, the current is measured at different voltages to generate a polarogram curve and determine the concentration and nature of solutes present. The DME allows for a wide potential range and surface regeneration between drops.
Polarography is an electrochemical technique used to analyze reducible or oxidizable substances in solution. It involves varying the electric potential between a dropping mercury electrode and a reference electrode while monitoring the current. A polarogram is generated by plotting the current readings against the applied voltage. Key features of polarography include applied voltages between 0-2.5V and current values between 0.12-100 microamperes. Polarography finds applications in pharmaceutical analysis such as determining dissolved oxygen, trace metals in drugs, vitamins, hormones, antibiotics, and diagnosing cancer from blood serum.
Polarographic technique is applied for the qualitative or quantitative analysis of electroreducible or oxidisable elements or groups.
It is an electromechanical technique of analyzing solutions that measures the current flowing between two electrodes in the solution as well as the gradually increasing applied voltage to determine respectively the concentration of a solute and its nature.
The principle in polarography is that a gradually increasing negative potential (voltage) is applied between a polarisable and non-polarisable electrode and the corresponding current is recorded.
Polarisable electrode: Dropping Mercury electrode
Non-polarisable electrode: Saturated Calomel electrode
From the current-voltage curve (Sigmoid shape), qualitative and quantitative analysis can be performed. This technique is called as polarography, the instrument used is called as polarograph and the current-voltage curve recorded is called as polarogram
Polarography is a voltammetric technique that uses a dropping mercury electrode. It can be used to qualitatively and quantitatively analyze both inorganic and organic compounds. The technique involves measuring the current as the potential is varied between two electrodes, with the current peaks corresponding to reduction or oxidation reactions. Diffusion current is directly proportional to concentration and can be used for quantitative analysis. Polarography finds applications in fields like trace metal analysis, environmental analysis, clinical analysis, and organic structure determination.
The earliest voltammetric technique
Heyrovsky invented the original polarographic method in 1922, conventional direct current polarography (DCP).
It employs a dropping mercury electrode (DME) to continuously renew the electrode surface.
Diffusion is the mechanism of mass transport.
When an external potential is applied to a cell
containing a reducing substance such as CdCl2,
The following reaction will occur:
Cd2+ + 2e + Hg = Cd(Hg)
The technique depends on increasing the applied
voltage at a steady rate and simultaneously
record photographically the current-voltage
curve (polarogram)
The apparatus used is called a polarograph .
When an external potential is applied to a cell
containing a reducing substance such as CdCl2,
The following reaction will occur:
Cd2+ + 2e + Hg = Cd(Hg)
The technique depends on increasing the applied
voltage at a steady rate and simultaneously
record photographically the current-voltage
curve (polarogram)
The apparatus used is called a polarograph .
Capillary tube about 10-15cm
Int. diameter of 0.05mm
A vertical distance being maintained betwwen DME and the solution
Drop time of 1-5 seconds
Drop diameter 0.5mm
The supporting electrolyte
is a solution of (KNO3, NaCl, Na3PO4) in which the sample (which must be electroactive) is dissolved.
Function of the supporting electrolyte
It raises the conductivity of the solution.
It carries the bulk of the current so prevent the
migration of electroactive materials to working
electrode.
It may control pH
It may associate with the electroactive solute as
in the complexing of the metal ions by ligands.
Polarography is an electroanalytical technique invented in 1922 by Jaroslav Heyrovsky for which he won the Nobel Prize. It involves measuring the current in a solution under an applied potential using a dropping mercury electrode and a reference electrode such as SCE. Mercury is used as the working electrode due to its wide negative potential range and ability to regenerate its surface. A polarogram is generated by plotting current versus applied potential, showing residual, diffusion, and limiting currents. Polarography can be used for qualitative and quantitative analysis of metals, drugs, and other compounds.
This document discusses polarography, an electrochemical technique used to analyze solutions. It describes the principle of polarography which involves applying an increasing negative potential between a dropping mercury electrode and a reference electrode to generate a current-voltage curve. Qualitative and quantitative analysis can be performed based on characteristics of this polarogram such as half-wave potential and diffusion current. The document also outlines the instrumentation, types of mercury electrodes, applications including pharmaceutical analysis, and provides an equation relating diffusion current to analyte concentration.
This document discusses various electrochemical techniques including voltammetry and polarography. It describes how voltammetry works by plotting current as a function of applied potential. Polarography uses a mercury working electrode. Different electrode configurations (e.g. solid vs. dropping mercury electrode) and cell designs (e.g. 2-electrode vs. 3-electrode) are discussed. Various factors that influence the measurements including mass transport and potential excitations are also summarized.
Potentiometry passively measures the potential of a solution between two electrodes, affecting the solution very little in the process. One electrode is called the reference electrode and has a constant potential, while the other one is an indicator electrode whose potential changes with the composition of the sample. Therefore, the difference of potential between the two electrodes gives an assessment of the composition of the sample. Potentiometry usually uses indicator electrodes made selectively sensitive to the ion of interest, such as fluoride in fluoride selective electrodes, so that the potential solely depends on the activity of this ion of interest.
Potentiometry is one of the methods of electroanalytical chemistry. It is usually employed to find the concentration of a solute in solution. In potentiometric measurements, the potential between two electrodes is measured using a high impedance voltmeter An ion-selective electrode (ISE), also known as a specific ion electrode (SIE), is a transducer (or sensor) that converts the activity of a specific ion dissolved in a solution into an electrical potential. There are four main types of ion-selective membrane used in ion-selective electrodes (ISEs): glass, solid state, liquid based, and compound electrode.
Cyclic voltammetry is an electroanalytical technique that measures current during redox reactions at an electrode. It involves scanning the potential of a working electrode versus a reference electrode and measuring the current. The potential is ramped from an initial value to a set switching potential and back to the initial value. This process is repeated in cycles. A cyclic voltammogram plots the current response of the working electrode versus the applied potential and provides information about redox potentials and reaction reversibility. Reversible reactions produce symmetrical peaks while irreversible reactions have wider separation between peaks. Cyclic voltammetry is useful for studying electrode reaction mechanisms and kinetics.
Polarography and voltammetry are electroanalytical techniques that involve applying a potential to a working electrode and measuring the resulting current. Jaroslav Heyrovsky discovered polarography in 1922 and was awarded the Nobel Prize for it in 1959. Polarography uses a dropping mercury electrode as the working electrode, while voltammetry can use other electrodes like platinum. Both techniques involve varying the applied potential over time and analyzing the current-potential relationship known as a polarogram or voltammogram. Key parameters that can be determined include peak potentials, diffusion coefficients, and formal reduction potentials which provide qualitative and quantitative analysis of electroactive species in solution.
Similar to Electroanalytical chemistry polarography (20)
This document discusses cheminformatics and its applications. Cheminformatics combines chemistry and computer science to store and analyze chemical data for applications like drug discovery. It encompasses designing, organizing, analyzing and visualizing chemical information. Key topics covered include molecular representations, chemical databases, similarity searching, machine learning methods, and tools for molecular docking and drug discovery.
This document discusses geographical indications (GIs), including their definition, benefits, examples, registration process, challenges, and relationship to trademarks. Some key points:
- GIs identify goods that originate from a specific geographical region and possess qualities due to that origin. Examples include Basmati rice, Darjeeling tea, and Champagne.
- Registering a GI confers legal protection and promotes the economic prosperity of producers. It can boost exports and support rural development.
- The registration process involves filing an application representing producers, publishing the application for opposition, and registering approved GIs for 10-year periods.
- Challenges include low brand value, lack of awareness, and misuse of
1. Gas chromatography is a technique used to separate components of a mixture using their volatility. It involves two phases - a stationary phase and a mobile gas phase.
2. The basic components of a gas chromatograph are an injection port, column, detector, and recorder. The sample is injected and carried by the mobile gas phase through the column where separation occurs.
3. Separation is based on the difference in partitioning behavior of analytes between the stationary and mobile phases. Components with higher partition coefficients have longer retention times.
Errors in analysis can be either determinate (systematic) or indeterminate (random). Determinate errors are caused by faults in the analytical procedure or instruments and result in consistently inaccurate results. Common sources of determinate error include faulty instrumentation, contaminated reagents, incorrect analytical methods, and analyst errors. Determinate errors can be identified by comparing results to a known standard or independent analytical method, and the source of the error must then be determined and corrected to improve accuracy.
This document provides information about green chemistry. It discusses natural processes versus chemical processes and how green chemistry aims to make chemical processes more environmentally friendly. Some key points made include:
- Green chemistry seeks to prevent pollution by designing chemical synthesis and products to be benign.
- Natural processes are more environmentally friendly than traditional chemical processes which use toxic solvents and generate hazardous wastes.
- Green chemistry principles include using safer solvents like water or ionic liquids, performing solvent-free reactions, and using renewable feedstocks and benign catalysts.
- New techniques like microwave irradiation and ultrasound can help drive chemical reactions in a more energy efficient and atom economic manner.
1. The document introduces different types of dosage forms including solid, liquid, and semi-solid forms. Solid forms include tablets, capsules, powders, and granules. Liquid forms include solutions, emulsions, suspensions, syrups and elixirs. Semi-solid forms include ointments, gels, creams and pastes.
2. Dosage forms deliver drug molecules to sites of action in the body and provide benefits like accurate dosing, protecting drugs, and masking tastes. They are classified based on route of administration, physical form, and whether they are for oral, topical, inhaled or other uses.
3. Common excipients used in dosage forms are discussed
This document discusses various classes of antibiotics including penicillins, cephalosporins, macrolides, tetracyclines, aminoglycosides, and quinolones. It describes their mechanisms of action, common uses, and potential adverse effects. Specifically, it provides details on common drugs in each class, how they work at the cellular level to kill bacteria, infections they can treat, and side effects to monitor like ototoxicity and nephrotoxicity. The document stresses the importance of obtaining cultures before treatment and monitoring patients for both therapeutic responses and unwanted reactions.
This document discusses different types of assays used in drug analysis, including chemical, immunological, microbiological, and bioassays. It provides details on various chemical assay techniques such as photometry, colorimetry, spectrophotometry, fluorimetry, flame photometry, and different types of chromatography. It also explains the principles, types, and techniques of immunoassays like ELISA, radioimmunoassay, and fluoroimmunoassay. Microbiological assays and characteristics of good assay methods are briefly covered as well.
Dr. Gurumeet C Wadhawa discusses biological assays. An assay is a procedure used to qualitatively or quantitatively assess the presence, amount, or functional activity of a target entity. There are three main types of assays: chemical, immuno, and bioassays. Bioassays involve estimating the concentration or potency of a pharmaceutical drug using animal or human subjects. While less precise than chemical assays, bioassays are more sensitive and can be used when chemical methods are not available or applicable. Bioassays are used to standardize and quantify various biological substances and products.
Dr. Gurumeet C Wadhawa discusses biocatalysts such as enzymes and microbes. Enzymes are mostly proteins that catalyze biochemical reactions in living cells and have unique three-dimensional shapes that fit reactants. They are produced commercially by isolating microbial strains that naturally produce the desired enzyme and optimizing fermentation conditions. Biocatalysts are classified into six types based on the reactions they catalyze. Important enzymes in the human body include digestive enzymes and DNA polymerases. Biocatalysts have various industrial applications in fields such as pharmaceuticals, food processing, and cosmetics.
1. The document discusses drug discovery and development, outlining the need to address unmet medical needs like new diseases as well as the costs of existing therapies.
2. It describes the historical aspects of clinical trials and regulations dating back to the 1500s, and outlines the modern drug development process including discovery, preclinical studies, and clinical trials through the various phases.
3. The drug development pathway involves discovery, preclinical development including chemistry/pharmacology and toxicology studies on animals, and clinical development including Phase I-III trials on volunteers and patients, with the goal of regulatory approval and market introduction over approximately 10-15 years.
The FDA regulates food, drugs, medical devices and other products. It oversees the drug approval process which involves preclinical testing in animals, followed by Phase I-III clinical trials in humans to test safety, efficacy and side effects. If approved, the drug can be marketed and is monitored for side effects. The document outlines the drug approval process and regulations around generic drugs, biologics, manufacturing and product changes.
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The document provides an overview of the pharmaceutical sector and its key business units and functions. It discusses:
1) The pharmaceutical sector can be classified into two main groups - drug discovery and manufacturing. Manufacturing is further divided into active pharmaceutical ingredients, generics, and biologics production.
2) Drug discovery is the most important process and involves significant time and costs to develop new drugs. The manufacturing areas have departments like production, quality control, quality assurance, process development, and engineering services.
3) The roles and educational qualifications required vary across the different business units and functions, but generally include degrees in fields like chemistry, pharmacy, biotechnology, engineering, and business administration. Senior roles often require a PhD
The document discusses the mevalonate and methylerythritol phosphate pathways which are used by nature to synthesize terpenoids. Terpenoids are derived from isoprene units which can be joined in head-to-tail or head-to-head fashion, resulting in hemiterpenes, monoterpenes, sesquiterpenes, diterpenes, sesterterpenes, triterpenes, and tetraterpenes. The mevalonate pathway is important for synthesizing steroids while the methylerythritol phosphate pathway may be more commonly used in most organisms. A variety of natural terpenoids derived from these pathways are then discussed, including their structures
(i) Non-classical carbocations display delocalization of sigma bonds through 3-center-2-electron bonds in bridged systems. Neighboring group participation can assist reactions by donating electrons through lone pairs, pi bonds, aromatic rings, or sigma bonds.
(ii) The pinacol-pinacolone rearrangement involves the migration of an alkyl group from one carbon to another after the loss of a leaving group from a vicinal diol. The migration is assisted by delocalization of the carbocation intermediate onto the oxygen atom.
(iii) In asymmetrical glycols, the group with greater ability for carbocation delocalization, such as phenyl, will migrate preferentially over
The document provides an overview of solid phase synthesis. It describes how solid phase synthesis involves coupling reagents to an inert solid support to perform multi-step organic synthesis. The key steps include attaching the starting material to a resin via a linker, performing sequential reactions on the bound intermediate, then cleaving the final product from the resin. The Merrifield method from 1963 pioneered this technique by automating the synthesis of peptides on an insoluble polystyrene resin, enabling efficient purification and the potential for parallel reactions.
This document provides an overview of ultrasound assisted organic synthesis (sonochemistry). It begins by defining ultrasound and discussing how it is used to promote and accelerate various organic chemical reactions. Key advantages of sonochemistry include increased reaction rates and product yields. It then discusses several examples of specific reaction types (e.g. condensation, substitution, addition) that have been improved through ultrasonic irradiation. The document also covers experimental parameters that can be optimized in sonochemical reactions as well as various applications in fields like pharmaceuticals, materials science, and environmental chemistry. In closing, it briefly introduces the concept of supercritical fluids.
Spectrophotometry involves using a spectrophotometer to measure how much light is absorbed by a sample at different wavelengths. It relies on Beer's Law, which states that absorbance is directly proportional to concentration, path length, and absorptivity. A spectrophotometer directs light from a source through a sample and measures the intensity of the transmitted light, allowing the absorbance and concentration of the sample to be determined. Spectrophotometry is used in various applications including chemistry, medicine, and environmental monitoring.
The document discusses stability studies of drug formulations. It defines stability as the ability of a drug product to remain within established specifications over time under storage and usage conditions. Stability testing is conducted to determine shelf life, recommended storage conditions, and suitability of packaging. The main types of drug degradation discussed are physical degradation (changes in appearance, solubility) and chemical degradation (hydrolysis, oxidation). Specific examples of each type of degradation are provided.
Candidate young stellar objects in the S-cluster: Kinematic analysis of a sub...Sérgio Sacani
Context. The observation of several L-band emission sources in the S cluster has led to a rich discussion of their nature. However, a definitive answer to the classification of the dusty objects requires an explanation for the detection of compact Doppler-shifted Brγ emission. The ionized hydrogen in combination with the observation of mid-infrared L-band continuum emission suggests that most of these sources are embedded in a dusty envelope. These embedded sources are part of the S-cluster, and their relationship to the S-stars is still under debate. To date, the question of the origin of these two populations has been vague, although all explanations favor migration processes for the individual cluster members. Aims. This work revisits the S-cluster and its dusty members orbiting the supermassive black hole SgrA* on bound Keplerian orbits from a kinematic perspective. The aim is to explore the Keplerian parameters for patterns that might imply a nonrandom distribution of the sample. Additionally, various analytical aspects are considered to address the nature of the dusty sources. Methods. Based on the photometric analysis, we estimated the individual H−K and K−L colors for the source sample and compared the results to known cluster members. The classification revealed a noticeable contrast between the S-stars and the dusty sources. To fit the flux-density distribution, we utilized the radiative transfer code HYPERION and implemented a young stellar object Class I model. We obtained the position angle from the Keplerian fit results; additionally, we analyzed the distribution of the inclinations and the longitudes of the ascending node. Results. The colors of the dusty sources suggest a stellar nature consistent with the spectral energy distribution in the near and midinfrared domains. Furthermore, the evaporation timescales of dusty and gaseous clumps in the vicinity of SgrA* are much shorter ( 2yr) than the epochs covered by the observations (≈15yr). In addition to the strong evidence for the stellar classification of the D-sources, we also find a clear disk-like pattern following the arrangements of S-stars proposed in the literature. Furthermore, we find a global intrinsic inclination for all dusty sources of 60 ± 20◦, implying a common formation process. Conclusions. The pattern of the dusty sources manifested in the distribution of the position angles, inclinations, and longitudes of the ascending node strongly suggests two different scenarios: the main-sequence stars and the dusty stellar S-cluster sources share a common formation history or migrated with a similar formation channel in the vicinity of SgrA*. Alternatively, the gravitational influence of SgrA* in combination with a massive perturber, such as a putative intermediate mass black hole in the IRS 13 cluster, forces the dusty objects and S-stars to follow a particular orbital arrangement. Key words. stars: black holes– stars: formation– Galaxy: center– galaxies: star formation
Authoring a personal GPT for your research and practice: How we created the Q...Leonel Morgado
Thematic analysis in qualitative research is a time-consuming and systematic task, typically done using teams. Team members must ground their activities on common understandings of the major concepts underlying the thematic analysis, and define criteria for its development. However, conceptual misunderstandings, equivocations, and lack of adherence to criteria are challenges to the quality and speed of this process. Given the distributed and uncertain nature of this process, we wondered if the tasks in thematic analysis could be supported by readily available artificial intelligence chatbots. Our early efforts point to potential benefits: not just saving time in the coding process but better adherence to criteria and grounding, by increasing triangulation between humans and artificial intelligence. This tutorial will provide a description and demonstration of the process we followed, as two academic researchers, to develop a custom ChatGPT to assist with qualitative coding in the thematic data analysis process of immersive learning accounts in a survey of the academic literature: QUAL-E Immersive Learning Thematic Analysis Helper. In the hands-on time, participants will try out QUAL-E and develop their ideas for their own qualitative coding ChatGPT. Participants that have the paid ChatGPT Plus subscription can create a draft of their assistants. The organizers will provide course materials and slide deck that participants will be able to utilize to continue development of their custom GPT. The paid subscription to ChatGPT Plus is not required to participate in this workshop, just for trying out personal GPTs during it.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
Discovery of An Apparent Red, High-Velocity Type Ia Supernova at 𝐳 = 2.9 wi...Sérgio Sacani
We present the JWST discovery of SN 2023adsy, a transient object located in a host galaxy JADES-GS
+
53.13485
−
27.82088
with a host spectroscopic redshift of
2.903
±
0.007
. The transient was identified in deep James Webb Space Telescope (JWST)/NIRCam imaging from the JWST Advanced Deep Extragalactic Survey (JADES) program. Photometric and spectroscopic followup with NIRCam and NIRSpec, respectively, confirm the redshift and yield UV-NIR light-curve, NIR color, and spectroscopic information all consistent with a Type Ia classification. Despite its classification as a likely SN Ia, SN 2023adsy is both fairly red (
�
(
�
−
�
)
∼
0.9
) despite a host galaxy with low-extinction and has a high Ca II velocity (
19
,
000
±
2
,
000
km/s) compared to the general population of SNe Ia. While these characteristics are consistent with some Ca-rich SNe Ia, particularly SN 2016hnk, SN 2023adsy is intrinsically brighter than the low-
�
Ca-rich population. Although such an object is too red for any low-
�
cosmological sample, we apply a fiducial standardization approach to SN 2023adsy and find that the SN 2023adsy luminosity distance measurement is in excellent agreement (
≲
1
�
) with
Λ
CDM. Therefore unlike low-
�
Ca-rich SNe Ia, SN 2023adsy is standardizable and gives no indication that SN Ia standardized luminosities change significantly with redshift. A larger sample of distant SNe Ia is required to determine if SN Ia population characteristics at high-
�
truly diverge from their low-
�
counterparts, and to confirm that standardized luminosities nevertheless remain constant with redshift.
Evidence of Jet Activity from the Secondary Black Hole in the OJ 287 Binary S...Sérgio Sacani
Wereport the study of a huge optical intraday flare on 2021 November 12 at 2 a.m. UT in the blazar OJ287. In the binary black hole model, it is associated with an impact of the secondary black hole on the accretion disk of the primary. Our multifrequency observing campaign was set up to search for such a signature of the impact based on a prediction made 8 yr earlier. The first I-band results of the flare have already been reported by Kishore et al. (2024). Here we combine these data with our monitoring in the R-band. There is a big change in the R–I spectral index by 1.0 ±0.1 between the normal background and the flare, suggesting a new component of radiation. The polarization variation during the rise of the flare suggests the same. The limits on the source size place it most reasonably in the jet of the secondary BH. We then ask why we have not seen this phenomenon before. We show that OJ287 was never before observed with sufficient sensitivity on the night when the flare should have happened according to the binary model. We also study the probability that this flare is just an oversized example of intraday variability using the Krakow data set of intense monitoring between 2015 and 2023. We find that the occurrence of a flare of this size and rapidity is unlikely. In machine-readable Tables 1 and 2, we give the full orbit-linked historical light curve of OJ287 as well as the dense monitoring sample of Krakow.
2. VOLTAMMETRY
• Voltammetry is the general name given to a group of
electro analytical methods in which the current is
measured as a function of applied potential where in the
polarization of the indicator or working electrode is
enhanced.
• The field has been developed from polarography.
• The word polarography first recorded in 1935 – 1940
Polaro(graph) + graphy(field of study)
3. POLAROGRAPHY
It is an electrochemical technique of
analysing solutions that measure the
current flowing between two electrodes
in the solution as well as the gradually
increasing applied
voltage to determine respectively the
concentration of solute and its
nature.
Created by: Jaroslav Heyrovsky for that
he awarded Nobel Prize in
1959
Figure 1
4. POLAROGRAPHY
Is a method of analysis based on
the measurement of current
electrolysis of an electroactive
species at a given electrode potential
under controlled conditions.
It is the branch of voltammetry
where the working electrode is a
dropping mercury electrode (DME)
or a static mercury drop electrode
(SMDE)
Figure 2
5. CONTD.
..
In this method, a reference
electrode and an indicator electrode
are required.
Reference electrode- it is larger
Figure 3
Reference electrode
in size and non
polarized(depolarized)
Indicator electrode- it is smaller
in size and polarized
Figure 4
Indicator electrode
6. WHY REFERENCE ELECTRODE WITH LARGER
AREA AND INDICATOR ELECTRODE WITH
SMALLER AREA???
Indicator electrode: It is smaller in size and polarized
i.e it adopts the potential externally imposed on it.
Reference electrode : It is larger in size and non
polarized i.e it retains to a constant potential throughout
the measurement.
7. THE CONDITIONS FOR POLAROGRAPHIC
WAVE FORMATION.
1. Polarographic analysis :
carriedElectrolytic analysis
out under special conditions.
specific characteristics:
A、A polarized electrode
depolarized electrode are
and a
used as
working electrode & referenceelectrode
B. No stirring Incomplete
electrolysis (only a small amount of
analyte is consumed)
Figure 5
8. POLARIZED ELECTRODE AND DEPOLARIZED
ELECTRODE
If the electrode potential has great changes when infinite small current
flow through the electrode, such electrode is referred to as polarized
electrode. eg. DME
If the electrode potential does not change with current , such electrode
is called ideal depolarized electrode. eg. SCE
Figure 6
9. EXAMPLES OF MERCURY
ELECTRODES
In polarography, mercury is used
as a working electrode, mercury
it is a liquid. The working
electrode is often
suspended from the
a drop
end of a
capillary tube. Examples:
1. HMDE (Hanging mercury
drop electrode)
2. DME (dropping mercury
electrode)
3. SMDE (static mercurydrop
electrode)Figure 7
10. WHY MERCURY?
Mercury as working electrode is useful because:
It displays a wide negative potential range
Its surface is readily regenerated by producing a new
drop or film
Many metal ions can be reversibly reduced into it.
Figure 8
11. PRINCIPLE
:
Study of solutions or of electrode processes by means of
electrolysis with two electrodes, one polarizable and one
unpolarizable, the former formed by mercury regularly
dropping from capillary tube.
POLARIZED ELECTRODE: Dropping Mercury
Electrode (DME)
DEPOLARIZED ELECTRODE: Saturated Calomel
Electrode
12. CONT
D..
Mercury continuously
drops from reservoir
through a capillary tube
into the solution.
The optimum interval
between drops for most
analyses is between 2 and
5 seconds.
Figure 9
14. 8
Current is a function of
analyte concentration
how fast analyte moves to electrode surface
rate of electron transfer to sample
voltage, time...
Readou
t
volta
ge
Detect
or/
Transd
ucer/
Sensor
sign
al
Excita
tion
Proc
ess
Sample
Voltage is applied to
analyte; appreciable
current is measured
View current as
a function of
time or applied
voltage
Current is
transformed to
voltage by
electronics
CONCEPT
15. THREE ELECTRODE CELL
Three electrode cell:
Working, Reference,
Counter/ auxilliary
flows
and
between
counter
Potential
by potentiostat
current
working
electrodes.
controlled
between working and
reference electrodes.
Figure 12
16. CONTD...
Two special electrodes
Supporting electrolyte :Usually relatively higher
concentration of strong electrolytes (alkali metal salts)
serves as supporting electrolyte
Dissolved oxygen is usually removed by bubbling
nitrogen through the solution
Voltage scanning Under unstirred state, recording
current-voltage curve.
17. POLAROGRAPHIC
DATA
Obtained from an automatic recording instrument is called a
polarogram , and the trace is called a polarographic wave.
POLAROGRAM
of current versus potential in aIt is a graph
polarographic analysis.
3 categories:
collectively referred to as residual current
referred to as diffusion current resulting from the reduction
of the sample
called the limiting current
The diffusion current of a known concentration of reference
standard are first determined followed by the determination
of the diffusion current of the unknown concentration
18. POLAROGRAM
ir (residual current) which
is the current obtained
when no electrochemical
change takes place.
iav (average current/limiting
current)is the current
obtained by averaging
current values throughout
the life time of the drop
while
id (diffusion current) whichis the current resulting from the
diffusion of electroactive
species to the drop surface.Figure 13
19. LIMITING DIFFUSION CURRENT -- A BASIS OF
POLAROGRAPHICALLY QUANTITATIVE ANALYSIS
When the applied voltage exceeds the decomposition voltage,
diffusion-controlled current is expressed as:
i = K(C-C0)
When the applied voltage gets more negative, C0 →0, current
becomes only diffusion limited, then
id = KC
Id reaches a limiting value proportional to ion concentration
C in bulk solution, and do not changes with applied voltage
longer
21. HOW IT WORKS??
o The applied voltage is gradually increased, typically by
going to a more positive( more negative decomposing
potential)
o A small residual current is observed.
o When the voltage becomes great enough, reduction occurs
at the analytical electrode causing a current.
o The electrode is rapidly saturated so current production is
limited – based on diffusion of the analyte to the small
electrode.
22. HOW IT
WORKS??
The reduced species alters the surface of the
mercury electrode.
To prevent problems, the mercury surface is
renewed by “ knocking off ” a drop –
providing a fresh surface.
This results in an oscillation of the data as it
is collected.
23. THE DIFFUSION THEORY AND
POLAROGRAPHIC WAVE
EQUATION
We have already known:
id = KC
In above equations, K is called Ilkovic constant, it is
expressed as follows:
K = 607 n D1/2m2/3t1/6
Thus,
id = 607nD1/2m2/3t1/6C
24. From above, when temperature, matrix solution and
capillary characteristic are kept constant, id is
proportional to C.
Concentration of
electroactive
analyte (mmolL-1)
Drop time(sec)
id = 607nD1/2m2/3t1/6C
Number of
transferring
electrons in
electrode
reaction(e/mo
l)
Diffusion current
(μA)
Density of analyte
in solution(Cm2.sec-
1
)
Mercury mass
flow(mg. sec-1)
25. POLAROGRAPHIC WAVE EQUATION
E = E1/2 – RT/ nF ln(i/(id-1))
When i = ½ id , log term in above equation is equal to
called halfwavezero, corresponding potential is
potential E1/2
E1/2 independent on the concentration
basis of qualitative analysis
26. INTERFERENCE CURRENT IN
CLASSICAL DC
POLAROGRAPH
Residual current
(1) redox reactions of impurities in solution
(2) charging of Hg drop (non-faradic current / non-redox
current)
Migration current
The current produced by static attraction of the electrode
to sought-for ion
27. POLAROGRAPHIC MAXIMUM (OR MALFORMED PEAK )
Reproducible maxima often occur in CV curve unless
eliminated by the addition of suitable maximum
suppressor such as MC or gelatin.
Figure 15
Curve a is unsuppressed oxygen maximum curve b is the
oxygen wave in presence of gelatin.
28. OXYGEN WAVE
Dissolved oxygen is easily reduced at many working
electrodes. Thus an aqueous solution saturated with air
exhibits two distinct oxygen waves.
The first results from the reduction of oxygen to
hydrogen peroxide:
The second wave corresponds to the further reduction of
hydrogen peroxide:
30. FACTORS THAT AFFECT LIMITING
DIFFUSION CURRENT
Characteristics of capillary& pressure of Hg
viscosity
Composition of solution
Temperature
concentration Factors that affect Half
wave potential
Type and concentration of
supporting electrolyte
Temperature
Forming complex
31. ???
?
Why does Nitrogen gas pass through the solution
before elecctrolysis???
Pure Nitrogen is passed through the solution before
connecting the electrolysis so as to remove dissolved
oxygen and during purification process a current of pure
nitrogen is maintained over the surface of the solution.
33. APPLICATIONS
Polarography is used for determination of Oxygen
content of fluids including whole body fluids ,
fermentation liquors &milk for studying the respiration
rates of microorganisms
Several mercury containing antiseptics and insecticides
were determined polarographically
Hormones like thyroxine,insulin,adrenaline and several
sex hormones are estimated by polarography
It is used for the determination of antibiotics such as
pencillin,streptomycin and chloramphenicol
Several Alkaloids can also be estimatedby
polarography.
34. CONTD...
In electrochemistry polarography allows the measurement of
potentials and yields information about the rate of the
electrode process, adsorption, desorption phenomena.
Calculation of the rate constant is possible with
polarography in this way very fast reactions of order 105 –
1010 litre mol-1sec-1 can be determined.
Polarography prooved useful in mechanistic studies.
Elimination of Mannich bases, hydration of multiple bonds in
unsaturated ketones and aldolization are example studies.
35. CONTD
...
Inorganic applications:
◦ In inorganic analysis polarography is used
predominately for trace metal analysis like copper,
zinc, iron, lead, nickel, manganese etc..
◦ Composition of alloys
◦ Purity of elements
OBJECTIVE PARAMETER
MEASURED
Identity of element Half wave potential
Quantity of element Diffusion current
36. CONTD...
Organic applications:
Electroreducible or oxidisable functional group can be
determined by polarographic technique by using dme.
The functionl group can be inferred from Half wave
potential and the quantity of the substance can be
determined from diffusion current measurement.
example functional groups like Nitro and Nitroso
groups, azo and diazo compounds, aldehydes, ketone,
organic peroxides lactons, activated C=C some acids and
organo metalic compounds.
Multi stage reduction of groups like Nitro to Nitroso to
Hydroxyl amine to Amino group can also be achieved
37. CONTD
...
The following table gives examples of E1/2
of some compounds.
Functional group E1/2 (V)
Benzaldehyde -1.51V
Iso propyl phenyl ketone -1.82V
Aldehydes and ketones -1.3V to -2.0V
Nitro compounds -0.1V to -0.7V
39. CONTD
...
One of the easiest and most frequently encountered
organic reduction is that of the nitro group. In Nitro
furans and nitroimidazoles, for example the reaction is
40. EXAMPLES OF DRUGS ANALYSED BY
POLAROGRAPHY
◦ prazosin
◦ Nifedipine
• Felodipine
• Amlodipine
• Spiranolactone
• Digitoxin
• p- Benzoquinone
• Vitamin K and its derivatives
• Azo and diazo compounds
• Keto steroids
41. RFERENCE
S
A Textbook of pharmaceutical analysis
Third edition by A.connors pgno:154-172
Vogel’s Textbook of Quantitative chemical analysis by
J mendham;RC denney;JD Barnes;
M Thomas, B Sivasankar
sixth edition
pgno;361-387
Quantitative Analysis; sixth edition by
R.A.DY;Jr.A.l.underwood
Pgno:11-1 to 11-11
Practical pharmaceutical chemistry
fourth edition-part two ; edited by:
A.H Beckett T.B Stenlake Pgno209-242
43. PROCE
DUREReagents:
1. 1, 2, 3, 4 and 5 mM Cadmium
standards.
2. 2 M KCl solution.
3. 0.2% gelatin solution.
4. Distilled water.
44. PROCEDURE
Select the concentration from the list.
Click “Load Cadmium Sample” button.
Select “Scan Analysis”.
Click “Plot Graph”.
Select the unknown concentration from the
concentration list.
Repeat the steps 2, 3 and 4.
Enter the concentration values on the worksheet.
Plot calibration curve by clicking the “plot” button
on the worksheet.
Calculate the unknown concentration value from the
calibration curve.
45. ADVANT
AGES
1. Simple sample handling
2. Speed of analysis
3. High sensitivity
4. Comparable or better accuracy
5. Cheaper instrumentation and lower cost of
chemicals used
6. Limited used of environmentally unfriendly
organic solvents
46. ASSAY OF NITROFURANTOIN
ORAL SUSPENSION
Transfer an accurately measured volume of
Nitrofurantoin Oral Suspension
equivalent to about 50 mg of Nitrofurantoin to a 100 ml
volumetric flask.
Add 20 ml of dimethylformamide, agitate for 5 mins. add
electrolyte solution to volume.
Filter the solution discarding the first 25-30 ml of the
filtrate.
Pipet 3 ml of the clear filtrate into a 25ml volumetric
flask
Add 0.1 ml of gelatin solution to a polarographic cell
47. Insert the mercury electrode of a suitable polarography and record the
polarogram using a standard calomel electrode as the reference
electrode.
Determine the height of the diffusion current at -0.0 V.
Calculate the quantity in mg of Nitrofurantoin in each ml of the
suspension taken by the formula: 833(c/V) (idu)/ (ids).
which V =volume in
ml of the suspension
taken idu = diffusion
current of the
unknown solution
ids is that determined in a solution of USP Nitrofurantoin Reference
48. DATA AND
CALCULATION
exactly 10 ml of Oral Suspension was taken for the
assay. Polarogram of this dilution measured 12.45 cm. A
polarogram of a reference standard solution containing
0.06 mg/ml measured 12 cm. Calculate the mg of
Nitrofurantoin in the final dilution of Oral Suspension.
1) Determine the amount (mg) of Nitrofurantoin in the final
dilution.
Cu
=
= = 0.0622
mg/ml
2) Determine the volume in ml of the Oral Suspension
in the final dilution.
10 : 100 = X
: 3
X =
0.3
ml
0.3 : 25 = X
: 1 X =
0.012
ml
(Cs)
(cmu)
c
ms
0.06 mg/ml x
12.45
1
2
49. 3) THE AMOUNT OF
NITROFURANTOIN IN 100 ML OF
ORAL SUSPENSION IS:
0.0622 :
0.012
=
X =
X :
100
518
mg
50. PHARMACEUTICAL
APPLICATIONS
Dissolved oxygen and
peroxides
Trace metals and metal –
containing drugs
Antiseptics and insecticides
Vitamins
Hormones
Antibiotics
Alkaloids
Blood serum and cancer
diagnosis
52. COULOM
ETRIC
ANALYSIS
Defined as an electroanalytical method in
which the quantity consumed during an
electrolysis reaction is a measure of the
electroactive species being analyzed.
Objective:
- To measure accurately the quantity of
electricity consumed by the analyte
species during the quantitative
electrochemical reaction.
of
electricit
y
quantity
of
W= Qf =
M n
W = weight of
analyte M =
molecular weight
n= number of electrons involved in the
electrochemical
53.
54. By Karl Fischer
It is used to determine the amount of water in a sample.
It can determine concentrations of water on the order of
milligrams per liter.
It is used to find the amount of
water in substances such as butter,
sugar, cheese, paper, and
petroleum.
56. PROCE
DUREReagents:
1. 1, 2, 3, 4 and 5 mM Cadmium
standards.
2. 2 M KCl solution.
3. 0.2% gelatin solution.
4. Distilled water.
57. PROCEDURE
Select the concentration from the list.
Click “Load Cadmium Sample” button.
Select “Scan Analysis”.
Click “Plot Graph”.
Select the unknown concentration from the
concentration list.
Repeat the steps 2, 3 and 4.
Enter the concentration values on the worksheet.
Plot calibration curve by clicking the “plot” button
on the worksheet.
Calculate the unknown concentration value from the
calibration curve.
58. ADVANTAGES
1. Simple sample handling
2. Speed of analysis
3. High sensitivity
4. Comparable or better accuracy
5. Cheaper instrumentation and lower cost of
chemicals used
6. Limited used of environmentally unfriendly
organic solvents
59. ASSAY OF NITROFURANTOIN
ORAL SUSPENSION
Transfer an accurately measured volume of
Nitrofurantoin Oral Suspension
equivalent to about 50 mg of Nitrofurantoin to a 100 ml
volumetric flask.
Add 20 ml of dimethylformamide, agitate for 5 mins. add
electrolyte solution to volume.
Filter the solution discarding the first 25-30 ml of the
filtrate.
Pipet 3 ml of the clear filtrate into a 25ml volumetric
flask
Add 0.1 ml of gelatin solution to a polarographic cell
60. Insert the mercury electrode of a suitable polarography and record the
polarogram using a standard calomel electrode as the reference
electrode.
Determine the height of the diffusion current at -0.0 V.
Calculate the quantity in mg of Nitrofurantoin in each ml of the
suspension taken by the formula: 833(c/V) (idu)/ (ids).
which V =volume in
ml of the suspension
taken idu = diffusion
current of the
unknown solution
ids is that determined in a solution of USP Nitrofurantoin Reference
61. DATA AND
CALCULATION
exactly 10 ml of Oral Suspension was taken for the
assay. Polarogram of this dilution measured 12.45 cm. A
polarogram of a reference standard solution containing
0.06 mg/ml measured 12 cm. Calculate the mg of
Nitrofurantoin in the final dilution of Oral Suspension.
1) Determine the amount (mg) of Nitrofurantoin in the final
dilution.
Cu
=
= = 0.0622
mg/ml
2) Determine the volume in ml of the Oral Suspension
in the final dilution.
10 : 100 = X
: 3
X =
0.3
ml
0.3 : 25 = X
: 1 X =
0.012
ml
(Cs)
(cmu)
c
ms
0.06 mg/ml x
12.45
1
2
62. 3) THE AMOUNT OF NITROFURANTOIN IN 100 ML
OF ORAL SUSPENSION IS:
0.0622 : 0.012 =
X =
X : 100
518 mg
63. PHARMACEUTICAL
APPLICATIONS
Dissolved oxygen and
peroxides
Trace metals and metal –
containing drugs
Antiseptics and insecticides
Vitamins
Hormones
Antibiotics
Alkaloids
Blood serum and cancer
diagnosis