This document describes a kinetic spectrophotometric method using the H-point standard addition method (HPSAM) to simultaneously determine vanadium(IV) and vanadium(V) or selectively determine vanadium(IV) in the presence of vanadium(V). The method utilizes the difference in rate of complex formation between vanadium(IV) and vanadium(V) with xylenol orange under acidic conditions. Vanadium(IV) can be determined in the range of 0.2-5 μg/ml with accuracy and precision, even in the presence of excess vanadium(V) and other metal ions. The method was successfully applied to synthetic mixtures and real samples to simultaneously or selectively determine vanadium(IV
Indirect Simultaneous Kinetic Determination of Semicarbazide and Hydrazine in...Fatemeh Sedaghatpour
This document describes a method using the H-point standard addition method (HPSAM) for the simultaneous determination of semicarbazide and hydrazine. The method is based on the reduction of Cu2+ to Cu+ by semicarbazide and hydrazine in the presence of neocuproine, followed by complex formation between Cu+ and neocuproine, producing a colored complex. The difference in the rates of reduction allows for the simultaneous analysis of both analytes. The method was able to determine semicarbazide in the range of 0.5-3.75 mg/ml and hydrazine in the range of 0.5-5 mg/ml in synthetic mixtures with different
Analytical Method Development and Validation for the Estimation of Zolmitript...ijtsrd
In this work the authors have proposed a simple, specific, economic and accurate reverse phase liquid chromatographic method for the estimation of Zolmitriptan as an active pharmaceutical ingredient and in pharmaceutical formulation. The main objective of the current research paper is to To develop simple, precise and accurate RP HPLC method for Zolmitriptan also to validate the developed method as per ICH guideline Q2R1 and to explore the applicability of the method in finished product formulation for estimation of Zolmitriptan during its lifecycle. The objective was achieved by optimized condition with Phonemenex C18 column 150mm×4.6mm , 5µm. And mobile phase Phosphate buffer pH 3.5 85 Methanol 15. The separation was done with a flow rate of 0.9ml min, detection with 224nm. The retention was found to be 3.57 minute. LOD and LOQ were found to be 2.45 and 7.42 respectively. So in order to obtain the correct results various validations methods are performed to get the results. The results obtained from those validation methods are plotted in the form of the charts as well as the different curves. Mr. Rahul M. Sagde | Mr. Pawan N. Karwa | Mr. Vivek M. Thorat | Sanjay S. Jadhav "Analytical Method Development and Validation for the Estimation of Zolmitriptan by RP HPLC Method" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-3 | Issue-5 , August 2019, URL: https://www.ijtsrd.com/papers/ijtsrd26474.pdfPaper URL: https://www.ijtsrd.com/pharmacy/analytical-chemistry/26474/analytical-method-development-and-validation-for-the-estimation-of-zolmitriptan-by-rp-hplc-method/mr-rahul-m-sagde
Simultaneous Equation and Area Under the Curve Spectrophotometric Methods for...BRNSS Publication Hub
Two simple spectrophotometric methods were developed and validated for the determination of ranolazine hydrochloride in the presence of its base-induced degradation product, namely simultaneous equation method using two wavelengths of 272 and 249 nm method (A) and area under the curve method using two wavelength ranges of 267–277 nm and 244–254 nm method (B). The accuracy, precision, and linearity ranges of the planned methods were firm. The methods were validated and the specificity was assessed by analyzing synthetic mixtures containing the drug and it’s degradant. The two methods were useful for the determination of the cited drug in its pharmaceutical preparation and the obtained results were statistically compared with those of a reported method. The comparison shows that there is no important difference between the proposed methods and the reported method about both accuracy and precision.
IOSR Journal of Applied Physics (IOSR-JAP) is an open access international journal that provides rapid publication (within a month) of articles in all areas of physics and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in applied physics. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Quality control of drug fleroxacin dosage, its monitoring in biological fluids, and research of drug’s metabolism and action are an important analytical task.
Combined spectra problem (ir, nmr & mass) format of organic moleculesDr. Krishna Swamy. G
This document outlines experiments for using spectroscopy techniques like UV, IR, NMR, and mass spectrometry to determine the structure of organic compounds. It describes collecting spectroscopic data like IR spectra, 1H NMR spectra, 13C NMR spectra, and mass spectra for several unknown compounds. The data would be analyzed by identifying functional groups and interpreting chemical shifts, multiplicities, fragmentations to deduce molecular formulas and structures. The experiments aim to elucidate organic structures using various spectroscopy methods.
GASSCHROMATOGRAPHY, ADVANCED STUDY OF THE FOLLOWING AND THEIR APPLICATIONS, I...Dr. Ravi Sankar
GASSCHROMATOGRAPHY, ADVANCED STUDY OF THE FOLLOWING AND THEIR APPLICATIONS, INTRODUCTION, THEORY, COLUMN OPERATION,INSTRUMENTATION AND DETECTION,APPLICATIONS AND ADVANTAGES OF GC,PRINCIPLE OF SEPARATION IN GC, HOW GC MECHINE WORKS? COLUMN, DETECTORS.
BY P.RAVISANKAR, VIGNAN PHARMACY COLLEGE, VADLAMUDI, GUNTUR, ANDHRA PRADESH, INDIA.
Simultaneous estimation of meclizine and nicotinic acid by using RP-HPLCpharmaindexing
This document describes the development and validation of a reverse phase high performance liquid chromatography (RP-HPLC) method for the simultaneous estimation of Meclizine and Nicotinic acid. The method utilizes a mobile phase of acetonitrile and potassium dihydrogen phosphate buffer with a flow rate of 1.0 mL/min. The retention times were 3.01 minutes for Meclizine and 6.07 minutes for Nicotinic acid. The method was validated and found to be accurate, precise, specific, linear, robust, sensitive and able to quantify the drugs in tablet dosage forms without interference from other components.
Indirect Simultaneous Kinetic Determination of Semicarbazide and Hydrazine in...Fatemeh Sedaghatpour
This document describes a method using the H-point standard addition method (HPSAM) for the simultaneous determination of semicarbazide and hydrazine. The method is based on the reduction of Cu2+ to Cu+ by semicarbazide and hydrazine in the presence of neocuproine, followed by complex formation between Cu+ and neocuproine, producing a colored complex. The difference in the rates of reduction allows for the simultaneous analysis of both analytes. The method was able to determine semicarbazide in the range of 0.5-3.75 mg/ml and hydrazine in the range of 0.5-5 mg/ml in synthetic mixtures with different
Analytical Method Development and Validation for the Estimation of Zolmitript...ijtsrd
In this work the authors have proposed a simple, specific, economic and accurate reverse phase liquid chromatographic method for the estimation of Zolmitriptan as an active pharmaceutical ingredient and in pharmaceutical formulation. The main objective of the current research paper is to To develop simple, precise and accurate RP HPLC method for Zolmitriptan also to validate the developed method as per ICH guideline Q2R1 and to explore the applicability of the method in finished product formulation for estimation of Zolmitriptan during its lifecycle. The objective was achieved by optimized condition with Phonemenex C18 column 150mm×4.6mm , 5µm. And mobile phase Phosphate buffer pH 3.5 85 Methanol 15. The separation was done with a flow rate of 0.9ml min, detection with 224nm. The retention was found to be 3.57 minute. LOD and LOQ were found to be 2.45 and 7.42 respectively. So in order to obtain the correct results various validations methods are performed to get the results. The results obtained from those validation methods are plotted in the form of the charts as well as the different curves. Mr. Rahul M. Sagde | Mr. Pawan N. Karwa | Mr. Vivek M. Thorat | Sanjay S. Jadhav "Analytical Method Development and Validation for the Estimation of Zolmitriptan by RP HPLC Method" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-3 | Issue-5 , August 2019, URL: https://www.ijtsrd.com/papers/ijtsrd26474.pdfPaper URL: https://www.ijtsrd.com/pharmacy/analytical-chemistry/26474/analytical-method-development-and-validation-for-the-estimation-of-zolmitriptan-by-rp-hplc-method/mr-rahul-m-sagde
Simultaneous Equation and Area Under the Curve Spectrophotometric Methods for...BRNSS Publication Hub
Two simple spectrophotometric methods were developed and validated for the determination of ranolazine hydrochloride in the presence of its base-induced degradation product, namely simultaneous equation method using two wavelengths of 272 and 249 nm method (A) and area under the curve method using two wavelength ranges of 267–277 nm and 244–254 nm method (B). The accuracy, precision, and linearity ranges of the planned methods were firm. The methods were validated and the specificity was assessed by analyzing synthetic mixtures containing the drug and it’s degradant. The two methods were useful for the determination of the cited drug in its pharmaceutical preparation and the obtained results were statistically compared with those of a reported method. The comparison shows that there is no important difference between the proposed methods and the reported method about both accuracy and precision.
IOSR Journal of Applied Physics (IOSR-JAP) is an open access international journal that provides rapid publication (within a month) of articles in all areas of physics and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in applied physics. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Quality control of drug fleroxacin dosage, its monitoring in biological fluids, and research of drug’s metabolism and action are an important analytical task.
Combined spectra problem (ir, nmr & mass) format of organic moleculesDr. Krishna Swamy. G
This document outlines experiments for using spectroscopy techniques like UV, IR, NMR, and mass spectrometry to determine the structure of organic compounds. It describes collecting spectroscopic data like IR spectra, 1H NMR spectra, 13C NMR spectra, and mass spectra for several unknown compounds. The data would be analyzed by identifying functional groups and interpreting chemical shifts, multiplicities, fragmentations to deduce molecular formulas and structures. The experiments aim to elucidate organic structures using various spectroscopy methods.
GASSCHROMATOGRAPHY, ADVANCED STUDY OF THE FOLLOWING AND THEIR APPLICATIONS, I...Dr. Ravi Sankar
GASSCHROMATOGRAPHY, ADVANCED STUDY OF THE FOLLOWING AND THEIR APPLICATIONS, INTRODUCTION, THEORY, COLUMN OPERATION,INSTRUMENTATION AND DETECTION,APPLICATIONS AND ADVANTAGES OF GC,PRINCIPLE OF SEPARATION IN GC, HOW GC MECHINE WORKS? COLUMN, DETECTORS.
BY P.RAVISANKAR, VIGNAN PHARMACY COLLEGE, VADLAMUDI, GUNTUR, ANDHRA PRADESH, INDIA.
Simultaneous estimation of meclizine and nicotinic acid by using RP-HPLCpharmaindexing
This document describes the development and validation of a reverse phase high performance liquid chromatography (RP-HPLC) method for the simultaneous estimation of Meclizine and Nicotinic acid. The method utilizes a mobile phase of acetonitrile and potassium dihydrogen phosphate buffer with a flow rate of 1.0 mL/min. The retention times were 3.01 minutes for Meclizine and 6.07 minutes for Nicotinic acid. The method was validated and found to be accurate, precise, specific, linear, robust, sensitive and able to quantify the drugs in tablet dosage forms without interference from other components.
Microchimica Acta Volume 69 issue 3-4 1978 [doi 10.1007_bf01201734] M. A. Sek...Sekheta Bros Company
This document describes kinetic methods for determining ultramicro quantities of manganese(II), molybdenum(VI), and tungsten(VI) based on their catalytic effect on the oxidation of Azorubin S by hydrogen peroxide. The methods were found to determine these elements in the concentration ranges of 5.5-33 ng/ml for manganese, 1.3-8.1 μg/ml for molybdenum, and 5.9-44.1 μg/ml for tungsten, with relative standard deviations less than 11%, 9%, and 5% respectively. The oxidation reactions were determined to be first order with respect to the catalyst and zero order with respect to Azor
This document describes a method for determining the concentration of vanadium(V) in sediment samples. The method involves leaching vanadium(V) compounds from sediment samples using sodium carbonate solution, followed by analysis using electrothermal atomic absorption spectrometry (ET-AAS). The method was validated on certified reference materials PACS-2 and MESS-3, which are marine sediments with known total vanadium content. Approximately 19% of the total vanadium in PACS-2 and 5% in MESS-3 was found to be in the vanadium(V) form. Validation experiments showed quantitative recovery of vanadium(V) spikes added to the samples. The method provides an accurate means of determining vanadium(V)
Equilibrium and kinetic study on chromium (vi) removal from simulatedGJESM Publication
Gooseberry seed powder was investigated as a novel biosorbent for the removal of chromium (VI) from simulated wastewater. Batch experiments were conducted to determine the effects of parameters such as pH, contact time, initial metal concentration, and adsorbent dosage on chromium removal efficiency. Maximum removal of 96% was achieved under optimal conditions at pH 2 within 60 minutes of contact time. Adsorption isotherm and kinetic models were applied to understand the adsorption mechanism, with the data fitting well to the Langmuir isotherm model and pseudo-second order kinetic model. The results indicate that gooseberry seed powder has potential as an effective and economical adsorbent for chromium removal.
IOSR Journal of Applied Chemistry (IOSR-JAC) is an open access international journal that provides rapid publication (within a month) of articles in all areas of applied chemistry and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in Chemical Science. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
This document describes the development and validation of an RP-HPLC method for the simultaneous analysis of diclofenac sodium and rabeprazole sodium without the need for an internal standard. The method utilizes a C8 column with a mobile phase of triethyl amine buffer (pH 5):acetonitrile (50:50 v/v) at a flow rate of 2 mL/min. Validation showed the method to be linear, accurate, precise, sensitive and stable. The method was applied to a pharmaceutical formulation containing both drugs with recoveries from 98-100%.
Development and validation of hplc method for determination of theophylline a...IJSIT Editor
A stable, simple, rapid, precise, accurate HPLC method for analysis of Theophyllinee and 1-Methyl
Uric Acid was developed and validated as per ICH guidelines without need of any internal standard.
Separation was carried out using X’terra RP18 (250*4.6) mm, 5µ column with potassium dihydrogen
orthophosphate buffer (pH 3): acetonitrile (30:70 v/v) as mobile phase with flow rate 1 mL min-1. The
parameters studied were retention time, linearity and range, accuracy, precision. The proposed method can
be used for determination of Theophylline and 1-Methyl Uric Acid from Human plasma.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
analytical techniques for estimation of organic compoundsRabia Aziz
more chemistry contents are available
1. pdf file on Termmate: https://www.termmate.com/rabia.aziz
2. YouTube: https://www.youtube.com/channel/UCKxWnNdskGHnZFS0h1QRTEA
3. Facebook: https://web.facebook.com/Chemist.Rabia.Aziz/
4. Blogger: https://chemistry-academy.blogspot.com/
ANALYTICAL TECHNIQUES FOR ESTIMATION OF ORGANIC COMPOUNDS
Validation of an extraction technique based on tributyl phosphateNasir Othman
This document describes the validation of an extraction technique using tributyl phosphate (TBP) for the determination of lead (Pb) in water samples. The extraction was optimized at pH 9-11, shaking time of 2-5 minutes, and 0.04M nitric acid as the stripping agent. Validation criteria such as recovery, linearity, accuracy, precision, detection limits, and robustness were evaluated. The technique showed high accuracy with 100% recovery and good linearity (R2=0.9969). Precision was good with relative standard deviations below 20%. The method detection limit was 4.43 μg/L and limit of quantification was 14.75 μg/L. Application to water samples from six sites on the Lang
1) Gas chromatography mass spectrometry (GC-MS) is a hyphenated technique that combines gas chromatography and mass spectrometry to identify different molecules within a sample.
2) GC separates the components in a mixture through partitioning between a mobile and stationary phase, while MS identifies molecules by detecting their mass.
3) Common ionization techniques used in GC-MS include electron impact and chemical ionization. Mass analyzers like quadrupole, ion trap, and time-of-flight are used to detect ions.
4) GC-MS has applications in pharmaceutical analysis, forensics, anti-doping testing, and newborn screening for inborn errors of metabolism.
This document discusses recent advancements in impurity profiling. It defines impurity profiling and outlines the importance of identifying impurities. The history of instrumental analysis for impurity identification is reviewed. A systematic approach to impurity profiling is presented, including thresholds for identification, qualification, and reporting. Methods for isolation and identification of impurities are described, including case studies. Both classical and modern methodologies are covered, with examples of separation techniques like HPLC, TLC, and capillary electrophoresis.
The document summarizes a jar test experiment conducted on water from the Kanawha River to determine the optimum dosage of alum coagulant. Six jars were dosed with varying amounts of alum from 10-60 mg/L. The pH, alkalinity, total solids, and turbidity were measured for each jar. The results showed that a dosage of 40 mg/L alum produced the lowest total solids and turbidity, indicating it was the optimum dosage for treatment of water from this source.
The document summarizes research on using functionalized multi-walled carbon nanotubes (MWCNTs) to remove chromium (Cr3+) ions from wastewater through adsorption. The researchers found that MWCNTs achieved 99.83% removal of Cr3+ ions at an optimum dosage of 25 mg in a pH 6 solution. Equilibrium adsorption experiments showed that the Langmuir isotherm model fit the data better than the Freundlich model, indicating monolayer adsorption of Cr3+ ions onto the MWCNT surfaces. Fourier transform infrared spectroscopy characterization confirmed the presence of functional groups like carboxyl that contribute to the adsorption of Cr3+ ions.
This paper studied the competitive adsorption of nitrate and oxalic acid on TiO2. It found that while nitrate had a higher Langmuir adsorption coefficient, oxalic acid adsorbed about 10 times more due to its ability to bind in two ways. In competitive adsorption, oxalic acid preferentially adsorbed, inhibiting nitrate uptake by up to 93% at higher oxalic acid concentrations. This inhibition could reduce the effectiveness of photocatalytic nitrate remediation, suggesting surface modification may be needed to enhance nitrate adsorption for faster reaction rates.
Ph.D. viva voce presentation on Anti-diabetics and statinsDr Sravani Karumudi
The document describes the development and validation of analytical methods for the estimation of anti-diabetic and statin drugs. It includes UV spectroscopic, colorimetric and stability-indicating RP-HPLC methods developed for the estimation of rosuvastatin calcium, pitavastatin calcium, empagliflozin, canagliflozin, ertugliflozin/metformin, and empagliflozin/linagliptin in bulk and pharmaceutical formulations. It also describes an in-vitro bioanalytical RP-HPLC method developed for the estimation of empagliflozin in human plasma. The methods were validated as per ICH guidelines and found to be accurate, precise, specific
This document describes the development of an enzymatic biosensing system to detect hydrogen sulfide (H2S) based on the inhibitory effect of H2S on the activity of ascorbate oxidase (AOx). Ascorbate oxidase was immobilized on a nylon membrane using glutaraldehyde. The immobilization parameters, including glutaraldehyde concentration and pH, were optimized using experimental design to achieve the fastest steady-state reaction time of 55 seconds. The biosensing system showed a linear response to H2S concentrations between 1-15 mg/L. Common ions like Fe3+ and SO42- had little effect on the sensor's ability to detect H2S. The sensor could retain
Mechanism of the Reaction of Plasma Albumin with Formaldehyde in Ethanol - Wa...IOSR Journals
The Spectrophotometric determination of the acid dissociation/ionisation constant (pKa) of plasma albumin-formaldehyde adduct in both water solution and Ethanol solutions was carried out in this study. The pKa values obtained in both media were used to establish the Bronsted-linear type constants from plots of pKa against logarithm of second order rate constants obtained at varying pHs in the study. The result of the pKa values obtained in both water solution and ethanol-water mixtures were found to be in the range of 5.0 - 8.0. This pointed to the fact that only lysine residue with pKa value 8.3 that might have possibly reacted with formaldehyde in this reaction of all the known amino acid residues in plasma albumin. The corresponding Brønsted-type plots proportionality constants (β) for the reaction in water and ethanol-water mixtures were found to be β = 0.059 and 0.0057 respectively. The reaction mechanisms that have low values for proportionality constants α or β are considered to have a transition state closely resembling the reactant with little proton transfer (Cox et al, 1988). Thus, one would suggest that the cross-linking of formaldehyde with plasma albumin in water and ethanol-water mixtures proceeds through little proton transfer
Kinetic Study of Polymerization of Methyl Methacrylate Initiated by Ce(IV) – ...IRJET Journal
1. The document describes a kinetic study of the polymerization of methyl methacrylate initiated by the Ce(IV)–vanillin redox system.
2. The effects of various reactants like Ce(IV), vanillin, H+, and reaction conditions like temperature, ionic strength, and micellar phase on the rate of polymerization and Ce(IV) consumption were examined.
3. The results show that the rate of polymerization increases with increasing concentrations of Ce(IV) and vanillin, and is dependent on [H+], while being independent of changes in [H+]. The activation and thermodynamic parameters were calculated from Arrhenius and Eyring plots.
This document analyzes the magnesium isotopic compositions of 22 differentiated meteorites from 7 types of achondrites and pallasite meteorites. It finds:
1) Achondrites have d26Mg values ranging from -0.369‰ to -0.158‰, with most compositions similar and showing no significant isotopic fractionation.
2) However, some angrites and howardite-eucrite-diogenite (HED) meteorites have slightly heavier Mg isotopic compositions, possibly due to impact evaporation or higher clinopyroxene abundances.
3) The average Mg isotopic composition of achondrites (-0.246‰) is indistinguish
Esencia Maya es una cadena de tiendas de ropa y artesanías con alta rotación de personal del 35%. El área con mayor rotación es ventas con 45%. El objetivo es identificar las causas y disminuir la rotación al 27% mediante nueve actividades como encuestas de clima laboral, inducción de empleados, evaluaciones, capacitación y actividades deportivas para retener el talento. Se estima que las ventas aumentarán en un 80% con esta estrategia.
El documento describe varias redes sociales populares como Facebook, YouTube, WhatsApp, QQ, WeChat, Qzone, Instagram, Sina Weibo, LinkedIn, Twitter, Google+, Line, Tagged, Habbo, Hi5, Tumblr, SoundCloud y Badoo. Cada una tiene características únicas como compartir videos, mensajería, blogs, fotos, música y conectar a usuarios de negocios y para conocer nuevas personas.
Microchimica Acta Volume 69 issue 3-4 1978 [doi 10.1007_bf01201734] M. A. Sek...Sekheta Bros Company
This document describes kinetic methods for determining ultramicro quantities of manganese(II), molybdenum(VI), and tungsten(VI) based on their catalytic effect on the oxidation of Azorubin S by hydrogen peroxide. The methods were found to determine these elements in the concentration ranges of 5.5-33 ng/ml for manganese, 1.3-8.1 μg/ml for molybdenum, and 5.9-44.1 μg/ml for tungsten, with relative standard deviations less than 11%, 9%, and 5% respectively. The oxidation reactions were determined to be first order with respect to the catalyst and zero order with respect to Azor
This document describes a method for determining the concentration of vanadium(V) in sediment samples. The method involves leaching vanadium(V) compounds from sediment samples using sodium carbonate solution, followed by analysis using electrothermal atomic absorption spectrometry (ET-AAS). The method was validated on certified reference materials PACS-2 and MESS-3, which are marine sediments with known total vanadium content. Approximately 19% of the total vanadium in PACS-2 and 5% in MESS-3 was found to be in the vanadium(V) form. Validation experiments showed quantitative recovery of vanadium(V) spikes added to the samples. The method provides an accurate means of determining vanadium(V)
Equilibrium and kinetic study on chromium (vi) removal from simulatedGJESM Publication
Gooseberry seed powder was investigated as a novel biosorbent for the removal of chromium (VI) from simulated wastewater. Batch experiments were conducted to determine the effects of parameters such as pH, contact time, initial metal concentration, and adsorbent dosage on chromium removal efficiency. Maximum removal of 96% was achieved under optimal conditions at pH 2 within 60 minutes of contact time. Adsorption isotherm and kinetic models were applied to understand the adsorption mechanism, with the data fitting well to the Langmuir isotherm model and pseudo-second order kinetic model. The results indicate that gooseberry seed powder has potential as an effective and economical adsorbent for chromium removal.
IOSR Journal of Applied Chemistry (IOSR-JAC) is an open access international journal that provides rapid publication (within a month) of articles in all areas of applied chemistry and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in Chemical Science. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
This document describes the development and validation of an RP-HPLC method for the simultaneous analysis of diclofenac sodium and rabeprazole sodium without the need for an internal standard. The method utilizes a C8 column with a mobile phase of triethyl amine buffer (pH 5):acetonitrile (50:50 v/v) at a flow rate of 2 mL/min. Validation showed the method to be linear, accurate, precise, sensitive and stable. The method was applied to a pharmaceutical formulation containing both drugs with recoveries from 98-100%.
Development and validation of hplc method for determination of theophylline a...IJSIT Editor
A stable, simple, rapid, precise, accurate HPLC method for analysis of Theophyllinee and 1-Methyl
Uric Acid was developed and validated as per ICH guidelines without need of any internal standard.
Separation was carried out using X’terra RP18 (250*4.6) mm, 5µ column with potassium dihydrogen
orthophosphate buffer (pH 3): acetonitrile (30:70 v/v) as mobile phase with flow rate 1 mL min-1. The
parameters studied were retention time, linearity and range, accuracy, precision. The proposed method can
be used for determination of Theophylline and 1-Methyl Uric Acid from Human plasma.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
analytical techniques for estimation of organic compoundsRabia Aziz
more chemistry contents are available
1. pdf file on Termmate: https://www.termmate.com/rabia.aziz
2. YouTube: https://www.youtube.com/channel/UCKxWnNdskGHnZFS0h1QRTEA
3. Facebook: https://web.facebook.com/Chemist.Rabia.Aziz/
4. Blogger: https://chemistry-academy.blogspot.com/
ANALYTICAL TECHNIQUES FOR ESTIMATION OF ORGANIC COMPOUNDS
Validation of an extraction technique based on tributyl phosphateNasir Othman
This document describes the validation of an extraction technique using tributyl phosphate (TBP) for the determination of lead (Pb) in water samples. The extraction was optimized at pH 9-11, shaking time of 2-5 minutes, and 0.04M nitric acid as the stripping agent. Validation criteria such as recovery, linearity, accuracy, precision, detection limits, and robustness were evaluated. The technique showed high accuracy with 100% recovery and good linearity (R2=0.9969). Precision was good with relative standard deviations below 20%. The method detection limit was 4.43 μg/L and limit of quantification was 14.75 μg/L. Application to water samples from six sites on the Lang
1) Gas chromatography mass spectrometry (GC-MS) is a hyphenated technique that combines gas chromatography and mass spectrometry to identify different molecules within a sample.
2) GC separates the components in a mixture through partitioning between a mobile and stationary phase, while MS identifies molecules by detecting their mass.
3) Common ionization techniques used in GC-MS include electron impact and chemical ionization. Mass analyzers like quadrupole, ion trap, and time-of-flight are used to detect ions.
4) GC-MS has applications in pharmaceutical analysis, forensics, anti-doping testing, and newborn screening for inborn errors of metabolism.
This document discusses recent advancements in impurity profiling. It defines impurity profiling and outlines the importance of identifying impurities. The history of instrumental analysis for impurity identification is reviewed. A systematic approach to impurity profiling is presented, including thresholds for identification, qualification, and reporting. Methods for isolation and identification of impurities are described, including case studies. Both classical and modern methodologies are covered, with examples of separation techniques like HPLC, TLC, and capillary electrophoresis.
The document summarizes a jar test experiment conducted on water from the Kanawha River to determine the optimum dosage of alum coagulant. Six jars were dosed with varying amounts of alum from 10-60 mg/L. The pH, alkalinity, total solids, and turbidity were measured for each jar. The results showed that a dosage of 40 mg/L alum produced the lowest total solids and turbidity, indicating it was the optimum dosage for treatment of water from this source.
The document summarizes research on using functionalized multi-walled carbon nanotubes (MWCNTs) to remove chromium (Cr3+) ions from wastewater through adsorption. The researchers found that MWCNTs achieved 99.83% removal of Cr3+ ions at an optimum dosage of 25 mg in a pH 6 solution. Equilibrium adsorption experiments showed that the Langmuir isotherm model fit the data better than the Freundlich model, indicating monolayer adsorption of Cr3+ ions onto the MWCNT surfaces. Fourier transform infrared spectroscopy characterization confirmed the presence of functional groups like carboxyl that contribute to the adsorption of Cr3+ ions.
This paper studied the competitive adsorption of nitrate and oxalic acid on TiO2. It found that while nitrate had a higher Langmuir adsorption coefficient, oxalic acid adsorbed about 10 times more due to its ability to bind in two ways. In competitive adsorption, oxalic acid preferentially adsorbed, inhibiting nitrate uptake by up to 93% at higher oxalic acid concentrations. This inhibition could reduce the effectiveness of photocatalytic nitrate remediation, suggesting surface modification may be needed to enhance nitrate adsorption for faster reaction rates.
Ph.D. viva voce presentation on Anti-diabetics and statinsDr Sravani Karumudi
The document describes the development and validation of analytical methods for the estimation of anti-diabetic and statin drugs. It includes UV spectroscopic, colorimetric and stability-indicating RP-HPLC methods developed for the estimation of rosuvastatin calcium, pitavastatin calcium, empagliflozin, canagliflozin, ertugliflozin/metformin, and empagliflozin/linagliptin in bulk and pharmaceutical formulations. It also describes an in-vitro bioanalytical RP-HPLC method developed for the estimation of empagliflozin in human plasma. The methods were validated as per ICH guidelines and found to be accurate, precise, specific
This document describes the development of an enzymatic biosensing system to detect hydrogen sulfide (H2S) based on the inhibitory effect of H2S on the activity of ascorbate oxidase (AOx). Ascorbate oxidase was immobilized on a nylon membrane using glutaraldehyde. The immobilization parameters, including glutaraldehyde concentration and pH, were optimized using experimental design to achieve the fastest steady-state reaction time of 55 seconds. The biosensing system showed a linear response to H2S concentrations between 1-15 mg/L. Common ions like Fe3+ and SO42- had little effect on the sensor's ability to detect H2S. The sensor could retain
Mechanism of the Reaction of Plasma Albumin with Formaldehyde in Ethanol - Wa...IOSR Journals
The Spectrophotometric determination of the acid dissociation/ionisation constant (pKa) of plasma albumin-formaldehyde adduct in both water solution and Ethanol solutions was carried out in this study. The pKa values obtained in both media were used to establish the Bronsted-linear type constants from plots of pKa against logarithm of second order rate constants obtained at varying pHs in the study. The result of the pKa values obtained in both water solution and ethanol-water mixtures were found to be in the range of 5.0 - 8.0. This pointed to the fact that only lysine residue with pKa value 8.3 that might have possibly reacted with formaldehyde in this reaction of all the known amino acid residues in plasma albumin. The corresponding Brønsted-type plots proportionality constants (β) for the reaction in water and ethanol-water mixtures were found to be β = 0.059 and 0.0057 respectively. The reaction mechanisms that have low values for proportionality constants α or β are considered to have a transition state closely resembling the reactant with little proton transfer (Cox et al, 1988). Thus, one would suggest that the cross-linking of formaldehyde with plasma albumin in water and ethanol-water mixtures proceeds through little proton transfer
Kinetic Study of Polymerization of Methyl Methacrylate Initiated by Ce(IV) – ...IRJET Journal
1. The document describes a kinetic study of the polymerization of methyl methacrylate initiated by the Ce(IV)–vanillin redox system.
2. The effects of various reactants like Ce(IV), vanillin, H+, and reaction conditions like temperature, ionic strength, and micellar phase on the rate of polymerization and Ce(IV) consumption were examined.
3. The results show that the rate of polymerization increases with increasing concentrations of Ce(IV) and vanillin, and is dependent on [H+], while being independent of changes in [H+]. The activation and thermodynamic parameters were calculated from Arrhenius and Eyring plots.
This document analyzes the magnesium isotopic compositions of 22 differentiated meteorites from 7 types of achondrites and pallasite meteorites. It finds:
1) Achondrites have d26Mg values ranging from -0.369‰ to -0.158‰, with most compositions similar and showing no significant isotopic fractionation.
2) However, some angrites and howardite-eucrite-diogenite (HED) meteorites have slightly heavier Mg isotopic compositions, possibly due to impact evaporation or higher clinopyroxene abundances.
3) The average Mg isotopic composition of achondrites (-0.246‰) is indistinguish
Esencia Maya es una cadena de tiendas de ropa y artesanías con alta rotación de personal del 35%. El área con mayor rotación es ventas con 45%. El objetivo es identificar las causas y disminuir la rotación al 27% mediante nueve actividades como encuestas de clima laboral, inducción de empleados, evaluaciones, capacitación y actividades deportivas para retener el talento. Se estima que las ventas aumentarán en un 80% con esta estrategia.
El documento describe varias redes sociales populares como Facebook, YouTube, WhatsApp, QQ, WeChat, Qzone, Instagram, Sina Weibo, LinkedIn, Twitter, Google+, Line, Tagged, Habbo, Hi5, Tumblr, SoundCloud y Badoo. Cada una tiene características únicas como compartir videos, mensajería, blogs, fotos, música y conectar a usuarios de negocios y para conocer nuevas personas.
This document is a resume for Shiva Singh seeking an IT job. It summarizes his professional qualifications including a Master's in Computer Application and Visual C# certification. It also lists his academic qualifications and projects done including a Java chat server mini project and an E-examination project built with C#.Net and SQL Server. It outlines his technical skills in software, databases, operating systems and languages. It provides details on his communication skills, activities and personal details.
Magnesium isotopic compositions of international geostandardsFatemeh Sedaghatpour
This document reports magnesium isotopic compositions for 24 international geological reference materials measured with high precision and accuracy. The long-term reproducibility of the measurements is ≤0.07‰ for δ26Mg and ≤0.05‰ for δ25Mg based on analyses of olivine and seawater samples over 4 years. A comprehensive dataset of Mg isotopic compositions for various rock types, minerals, and seawater is presented to serve as a reference for quality control and comparison between laboratories performing high-precision Mg isotope analysis. Careful cleaning of ion exchange resins using hydrofluoric acid is required to achieve accurate results and avoid matrix effects.
Ionic Liquids Modify the Performance of Carbon Based Potentiometric SensorsFatemeh Sedaghatpour
This document describes a study that tested the performance of potentiometric sensors constructed with carbon ionic liquid electrodes (CILEs) compared to traditional carbon paste electrodes (CPEs). Two ionic liquids, N-octylpyridinium hexafluorophosphate and 1-butyl-3-methylimidazolium hexafluorophosphate, were used as binders in CILEs. The results showed that CILE-based sensors exhibited improved Nernstian slope, selectivity, response time, and response stability compared to CPE-based sensors. Specifically, a CILE containing 30% N-octylpyridinium hexafluorophosphate and 70% graphite
This document analyzes the magnesium isotopic compositions of 47 lunar samples including mare basalts, highland rocks, regolith breccias, and lunar soils. The samples show a range of magnesium isotopic values from -0.61‰ to 0.02‰ in mare basalts and -0.34‰ to -0.18‰ in highland rocks. Limited variation is observed among lunar soils and breccias, but large fractionation is seen between low-Ti and high-Ti basalts. Overall, the Moon has a magnesium isotopic composition indistinguishable from Earth and chondrites, suggesting homogeneous distribution in the solar system without fractionation during the Moon-forming giant impact
Single Step Calibration, Prediction and Real Samples Data Acquisition for Art...Fatemeh Sedaghatpour
The document describes the development of an artificial neural network model for the simultaneous determination of aluminum (Al(III)) and iron (III) using a charge-coupled device (CCD) camera. A single image was taken to obtain all calibration, prediction, and real sample data using chrome azurol S as the colorimetric reagent. Experimental conditions were optimized to reduce interference and increase sensitivity. The neural network was trained with a backpropagation algorithm using sigmoid transfer functions. Both Al(III) and Fe(III) could be determined between 0.25-4 μg/ml with good accuracy and precision. The method was also applied to synthetic alloy samples.
Tensammetric Analysis of Nonionic Surfactant Mixtures by Artificial Neural Ne...Fatemeh Sedaghatpour
1. An artificial neural network model was developed to analyze mixtures of four nonionic surfactants (Brij 30, 35, 56, and 96) using tensammetry.
2. Tensammetry measures the capacitive current of an electrode after surfactant adsorption. It was found to be sensitive for detecting the four Brij surfactants individually and in mixtures.
3. An artificial neural network was trained on tensammetry data from calibration mixtures to learn the relationships between peak currents and surfactant concentrations. It was then able to predict concentrations in new samples.
This document discusses iron isotope measurements of lunar samples, including the oldest lunar rock dunite 72 415. The key points are:
1) Dunite 72 415 has a surprisingly light iron isotope composition, in contrast to other lunar samples which are enriched in heavy iron isotopes compared to Earth.
2) Additional measurements of dunite 72 415 confirm this light iron isotope signature.
3) The earliest olivine accumulation in the lunar magma ocean may have been enriched in light iron isotopes, allowing the overall iron isotope composition of the Moon to match that of Earth.
A empresa de tecnologia anunciou um novo smartphone com câmera aprimorada, maior tela e melhor desempenho. O novo dispositivo também possui maior capacidade de armazenamento e bateria de longa duração. O lançamento do novo modelo está programado para o final deste ano.
Characterization of Antarctic micrometeorites by thermoluminescenceFatemeh Sedaghatpour
This document characterizes four Antarctic micrometeorites using thermoluminescence (TL). TL measurements found the micrometeorites have sensitivities ranging from 0.017 to 0.087 and similar TL peak temperatures and widths. Heating experiments on meteorite fragments showed the TL properties were not significantly affected by atmospheric passage. The TL properties of the micrometeorites closely resemble the CM chondrite MAC 87300 and terrestrial forsterites, suggesting they contain forsterite but do not match any known meteorite class. Scanning electron images and analyses found the micrometeorites consist of olivine, pyroxene, and iron oxides.
This document describes an interlaboratory comparison of magnesium isotopic compositions in 12 geological standards with compositions ranging from felsic to ultramafic. The standards were analyzed in five laboratories using multicollector inductively coupled plasma mass spectrometry. The key findings were:
- Magnesium isotopic compositions agreed within uncertainties for most standards between laboratories, but some mafic samples differed by up to 0.3‰.
- The interlaboratory differences did not correlate with matrix element concentrations and likely arose from variations in column chemistry procedures between labs.
- The study highlights the need for well-calibrated standards with matrices matching samples to reduce interlaboratory biases in magnesium isotope analysis.
Homogeneous magnesium isotopic composition of seawater an excellent geostanda...Fatemeh Sedaghatpour
This document investigates the homogeneity of magnesium isotopes in seawater by analyzing 40 seawater samples from the Gulf of Mexico and one sample from Hawaii using mass spectrometry. The results indicate the Mg isotopic composition of seawater is homogeneous both vertically and horizontally, with average values of d26Mg = -0.832 ± 0.068 and d25Mg = -0.432 ± 0.053 for the Gulf of Mexico samples and identical values for the Hawaii sample. Given seawater's homogeneous isotopic composition and ready availability, the document concludes it could serve as an excellent geostandard for assessing accuracy in high-precision magnesium isotope analysis.
Presenting a Succession planning how organisation to ensure leadership continuity retain and develop knowledge and intellectual capital for the future, and encourage individual employee growth and development.
Why ultra high performance liquid chromatography produces more tailing peaksFarzad Samie
This document discusses why ultra high performance liquid chromatography (UHPLC) produces more tailing peaks than high performance liquid chromatography (HPLC), despite providing better resolution of adjacent peaks. The key points are:
1) UHPLC uses smaller particle sizes (e.g. sub-2 μm) than HPLC (e.g. 3 μm particles), which results in higher theoretical plate counts and efficiency. However, when the same amount of sample is injected, UHPLC produces significantly higher tailing factor (Tf) values compared to HPLC separations.
2) Expressions are derived that describe how the Tf value changes with particle size and theoretical plate count. Additional expressions allow scaling the injection volume based on these parameters to
The document summarizes a new instrument called SIFT-MS (Selected Ion Flow Tube-Mass Spectrometer) that can perform real-time, quantitative, selective, and sensitive analysis of a wide range of volatile organic and inorganic compounds in air. It works by using reagent ions to collide and chemically ionize sample compounds, and then detecting and quantifying the resulting product ions. The instrument requires only carrier gas and can analyze over 1,000 compounds simultaneously without sample preparation. It could potentially analyze many of the compounds currently tested for in the laboratory with just one instrument, improving efficiency. The document recommends considering purchasing the instrument to help monitor air samples.
Design and Construction of a Simple and Reliable Temperature Control Viscomet...theijes
The International Journal of Engineering & Science is aimed at providing a platform for researchers, engineers, scientists, or educators to publish their original research results, to exchange new ideas, to disseminate information in innovative designs, engineering experiences and technological skills. It is also the Journal's objective to promote engineering and technology education. All papers submitted to the Journal will be blind peer-reviewed. Only original articles will be published.
This document discusses using in-situ UV-visible and Raman spectroscopy to characterize the state of a solid in multiphase gas-liquid-solid reactor systems. It presents experiments using these techniques on a slurry of particles and in a packed bubble column. An insoluble pH indicator deposited on particles and foam packing is used as a model system, as it exhibits different spectra depending on liquid pH. The results show the spectra from moving particles in a slurry can characterize the pH indicator state. Bubbles in the packed column interfere with spectra collection from the solid surface, but this interference is successfully removed using a new tolerance-and-averaging method.
This presentation was presented when I was MVSc 1st year student, hence this ppt will provide a piece of basic information about the use of Chromatography.in toxicology. Principle of its work and related terminology are explained in this ppt.
Limitations and Advantages in Assessing Adenovirus Homogeneity by Laser Light...KBI Biopharma
The document discusses methods for characterizing the homogeneity of adenovirus preparations using analytical techniques like light scattering and analytical ultracentrifugation. It finds that light scattering has limitations in accurately assessing particle size distribution and aggregation when measuring large virus particles like adenovirus. Analytical ultracentrifugation is able to provide higher resolution information about the adenovirus particle size distribution and detect different forms of structural heterogeneity.
This document summarizes a study of electron transfer reactions of the eight-coordinate vanadium complex bis-(N-hydroxyiminodiacetate)vanadium(IV) [V(HIDA)2]2–, which is a synthetic analog of the natural compound amavadin found in mushrooms. The self-exchange rate constant of the [V(HIDA)2]2–/– redox couple was determined using both Marcus theory calculations from oxidation/reduction cross reactions, and direct measurement using 51V NMR line broadening techniques. The average self-exchange rate constant was found to be 1.5 × 105 M–1 s–1, similar to that of amavadin itself. This suggests that
UV-vis. spectroscopy N HPLC (rilpivirine) by RJcharan.RJ Charan
This document outlines the development and validation of UV and HPLC methods for the analysis of Rilpivirine, an antiretroviral drug used to treat HIV. It discusses developing UV spectroscopy methods to determine the wavelength of maximum absorbance of Rilpivirine. It also discusses developing an HPLC method to separate and analyze Rilpivirine, including selecting the column, mobile phase, and detection wavelength. The goal is to validate these analytical techniques for accurate quantification of Rilpivirine in samples.
This document summarizes research on using ultrasound Doppler technique to analyze blood flow. An in vitro system was used to measure the frequency and amplitude of ultrasound signals scattered from a moving column of blood analog under varying flow conditions. The relationship between frequency shift, flow rate, and probe angle was determined using multiple regression. It was found that frequency shift correlated well with flow rate and probe angle but not vessel diameter. With knowledge of the probe angle, ultrasound Doppler can estimate blood flow velocity but not vessel diameter. The technique shows potential for non-invasive blood flow measurements in animals and humans.
Effects of Ionic Strength and pH on Arsenic Mobilization from Arsenopyrite_Ch...Chloe An
This document summarizes a study that investigated the effects of ionic strength and pH on arsenic mobilization from arsenopyrite in managed aquifer recharge systems. The study found that:
1) In sodium nitrate systems, the lowest arsenic levels occurred at pH 5 due to a balance between arsenic mobilization from dissolution and sorption by ferrihydrite; the highest levels were at pH 3 and 7.
2) In sodium chloride systems, arsenic levels were highest at lower pHs due to inhibited ferrihydrite formation from chloride; the lowest levels occurred at pH 7.
3) For sodium nitrate systems, arsenic levels were generally highest at 10mM ion
What is the Rate Law for the Crystal Violet Reaction327-43.docxalanfhall8953
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Application of uv visible spectroscopy in microbiologyFarhad Ashraf
UV-visible spectroscopy can be used to analyze various biomolecules and nitrogen compounds in microbiology. The interaction of electromagnetic radiation with matter allows for identification of unknown biomolecules based on their characteristic absorption spectra. Beer's law demonstrates that absorbance is directly proportional to concentration, allowing for quantification of substances. Total nitrogen can be determined by digesting all nitrogenous compounds to nitrate via autoclaving, then analyzing the nitrate concentration. Second derivative UV-visible spectroscopy provides an accurate technique for determining nitrate and total nitrogen in wastewater samples.
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Introduction Part Precision Measurements using Spectroscopy Aim.pdfbkbk37
The document discusses precision measurements using UV/Vis spectroscopy. It describes calibrating pipettes and volumetric flasks, then taking absorbance readings of a methyl orange solution using the calibrated equipment. Statistical analysis found pipettes had lower standard deviations, and thus higher precision, than volumetric flasks. The document also details determining the concentration of salicylate in a face wash using a reaction with Fe(III) ions and developing a calibration curve. A Job plot method was used to find the reaction stoichiometry. Data from repeated measurements was statistically analyzed to check if results came from the same population.
1) A kinetic method is proposed for the determination of uranium(VI) based on its catalytic action on the decomposition of hydrogen peroxide in alkaline media.
2) The method was optimized and the kinetic expression was derived. Uranium(VI) can be determined in the concentration range of 0.8 to 6.4 μg/ml using the tangent method.
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New RP HPLC method for the simultaneous estimation of sulbactum and ceftriaxo...SriramNagarajan19
A simple and selective LC method is described for the determination of Sulbactum and Ceftriaxone tablet dosage forms. Chromatographic separation was achieved on a C18 column using mobile phase consisting of a mixture of mixture of 60 volumes of 20mM Phosphate buffer pH 3.5: 40 volumes of Acetonitrile (60:40 v/v) with detection of 210 nm. Linearity was observed in the range 30-70 µg /ml for Sulbactum (r2 =0.9998) and 60-140µg /ml for Ceftriaxone (r2 =0.9983) for the amount of drugs estimated by the proposed methods was in good agreement with the label claim. The proposed methods were validated. The accuracy of the methods was assessed by recovery studies at three different levels. Recovery experiments indicated the absence of interference from commonly encountered pharmaceutical additives. The method was found to be precise as indicated by the repeatability analysis, showing %RSD less than 2. All statistical data proves validity of the methods and can be used for routine analysis of pharmaceutical dosage form.
Study the effect of adding pva on some physical properties of cmc polymer as ...Alexander Decker
This document studies the effect of adding polyvinyl alcohol (PVA) on various physical properties of carboxymethyl cellulose (CMC) polymer solutions. Several rheological properties (shear viscosity, relative viscosity, specific viscosity, reduced viscosity) and mechanical properties (ultrasonic velocity, absorption coefficient, relaxation time, bulk modulus) of CMC solutions of varying concentrations were measured before and after adding PVA. The results showed that most properties increased with higher CMC concentration but decreased after adding PVA, indicating interactions between the two polymer chains. Specifically, adding PVA enhanced ultrasonic absorption coefficient and reduced viscosity, relaxation time, and compressibility. The study suggests PVA addition can reduce water needs to achieve viscosity goals
This document describes a study that developed and optimized an ion-pair reverse-phase high-performance liquid chromatography coupled with inductively coupled plasma mass spectrometry (HPLC-ICP-MS) method for arsenic speciation in Chinese brake fern (Pteris vittata L.). The method was able to separate and detect four arsenic species (arsenite [As(III)], dimethyl arsenic acid (DMA), monomethyl arsenic (MMA), and arsenate [As(V)]) in a single run. This is the first study to show that Chinese brake fern can convert MMA to DMA via methylation. The optimized HPLC-ICP-MS method was then applied to
A HPLC-UV METHOD FOR DETEERMINATION OF THREE PESTICIDES IN WATERijac123
HPLC method is developed and validated for determination of three pesticides (abamectin, imidacloprid,
and β-cyfluthrin) in water. These pesticides are used widely in agriculture for crops protection, and may be
leached to the groundwater. Reversed-phase method with C18 column (5 µm, 250mm × 4.6 mm inner
diameter) using a mobile phase consisting of acetonitrile/water (v:v = 4:1) at a flow rate of 1.5 mL/min and
UV detection at 220 nm was used. This method is validated according to new methods which include
accuracy, precision, linearity and range, limit of detection and limit of quantitation. The current method
exhibits good linearity over the range of 1-1000 ppb for abamectin, 0.5-1000 ppb for imidacloprid, and
0.4-1000 ppb for ß-cyfluthrin with r2
greater than 0.990. The percentage recovery of the method at three
concentration levels (5, 100, and 1000 ppb) is within 97.6 to 101.5% for the three pesticides. Relative
standard deviation of the area of six replicate injections of each pesticide at three concentration levels (5.0,
100.0, and 1000.0 ppb) was found to be less than 1% which reflect the precision of the method. Limit of
quantitation of the three pesticides using this method is low (1.0, 0.5, and 0.4 ppb) for abamectin,
imidacloprid, and β-cyfluthrin, respectively which enables the determination of these three pesticides in
water at low concentration levels
Similar to Kinetic spectrophotometric determination of V(IV) in the presence of V(V) by H-point standard addition method (20)
2. 276 A. Safavi et al. / Analytica Chimica Acta 409 (2000) 275–282
selective, precise and inexpensive methods for the de-
termination of V(IV) in the presence of V(V) is very
important.
The H-point standard addition method (HPSAM)
is a modification of the standard addition method
that transforms the incorrigible error resulting from
the presence of a direct interference in the determi-
nation of an analyte into a constant systematic error.
This error can then be evaluated and eliminated. This
method also permits both proportional and constant
errors produced by the matrix of the sample to be
corrected directly. The basis of the method was es-
tablished previously [11,12]. Absorbance increments
as analytical signals were used when only the ana-
lyte concentration was required [13]. The method has
been applied to eliminate the blank bias error due
to the use of the absorbant blank [14,15], to liquid
chromatography [16] and to the analysis of kinetic
data [17], with time as an additional variable.
Two variants of HPSAM can be used for the treat-
ment of kinetic data [17]. One is applied when the
reaction of one component is faster than that of the
other or the latter does not take place at all. This vari-
ant of the method is based on the assumption that only
analyte X evolves with time and the other species Y
or interferents do not affect the analytical signal with
time. In this case the variables to be fixed are two
times t1 and t2 at which the species Y, which does
not evolve with time or over the range between these
times, should have the same absorbance. The other
variant of the method is used when the rate constants of
the two components are time-dependent. In this case,
the two species in a mixture, X and Y, evolve with time,
Cx (concentration of analyte) and Ay (the absorbance
of interference) can be calculated by plotting the ana-
lytical signal At1−t2 against the added concentration
of X at two wavelengths λ1 and λ2, provided that the
absorbances of the Y component at these two wave-
lengths are the same (AY ) and so are thus the At1−t2
values.
In this work the first variant of the H-point standard
addition method is suggested as a simple and selective
method for the determination of V(IV) in the presence
of V(V). This method is based on the difference in the
rate of complex formation of V(IV) and V(V) with
xylenol orange under acidic conditions.
The well-known metallochromic indicator, xylenol
orange (XO) [18,19] has been proposed for the colori-
metric determination of a number of metals [20–23].
It is evident that XO shows only slight selectivity,
so that direct determination of metal ions with XO
usually suffers from serious interferences. Although
XO has been used for the determination of vanadium
previously [23], to the best of our knowledge, the
complexation kinetics of V(IV) and XO were not
considered previously for selective determination of
V(IV) in the presence of V(V).
2. Experimental
2.1. Reagents
All chemicals used were of analytical reagent grade.
Triply distilled water was used throughout. Stock
vanadium(V) and (IV) solutions (1000 g ml−1), were
prepared from ammonium metavanadate and vanadyl
sulfate monohydrate (Fluka), respectively, and stan-
dardized [24,25]. XO stock solution (0.01 M) was
prepared from its disodium salt (Fluka). The working
solutions were diluted with water to the appropriate
concentrations. 1000 g ml−1 solutions of the studied
interfering ions were prepared from appropriate salts.
A buffer of pH 2 was prepared by using sodium citrate
and hydrochloric acid at appropriate concentrations
[26].
2.2. Apparatus
UV-visible absorbance spectra were recorded on a
Philips 8750 spectrophotometer. Measurements of pH
were made with Metrohm 691 pH meter using a com-
bined glass electrode. The absorbance measurements
as a function of time, at fixed wavelength, were made
with a Philips PU875 spectrophotometer attached to a
Pentium 200 MHz computer.
2.3. Procedure
2 ml of buffer solution, 0.2 ml of stock XO solu-
tion and appropriate volumes of V(IV) and V(V) were
added to a 5 ml volumetric flask and made up to the
mark with water. For each measurement, ca. 2 ml of
the above solution was transferred to a spectropho-
tometer cell and the variation of absorbance vs. time
3. A. Safavi et al. / Analytica Chimica Acta 409 (2000) 275–282 277
was recorded immediately. The absorbance was mea-
sured at 562 nm with 5 s time intervals for each sam-
ple. Simultaneous determination of V(IV) and V(V)
with HPSAM was performed by measuring the ab-
sorbances at just 60 and 240 s for each sample solution.
The concentration ranges of V(IV) and V(V) for the
construction of a HPSA calibration graph were 0.2–5
and 0.1–3.0 g ml−1, respectively. The same proce-
dure was repeated with 2 ml of samples such as blood
serum, river water, tap water or synthetic samples.
3. Results and discussion
HPSAM as a modified standard addition method
was proposed to obtain an unbiased analyte concentra-
tion when both analyte and interference are present in a
sample. This method can be applied to kinetic data for
the simultaneous determination of binary mixtures or
calculation of analyte concentrations completely free
from bias.
The rate of complex formation between XO and
V(IV) is slower than V(V) complex formation under
acidic conditions. Fig. 1 shows the change in visi-
ble absorption spectra of the XO–V(IV) system as a
function of time. The study on the influence of pH on
the rate of V(IV)–XO complex formation showed that
Fig. 1. Variation of visible absorption spectra of XO (3.0 × 10−4 M) solution in the presence of 2.0 g ml−1 V(IV), as a function of time.
Time interval 1 min.
the maximum change in absorbance in the fixed time
period (30–60 s) occurred at ca. pH = 2. The rate of
complex formation above pH 3 was so fast that the
complex formation reaction was almost complete be-
fore 30 s and thus the change in absorbance between
30 and 60 s was very small (Fig. 2). So, 562 nm and
pH 2 were selected for monitoring the kinetics of the
system. However, under the same condition, the com-
plexation of V(V) was very fast.
Fig. 3 shows the possible applicability of HPSAM
for the simultaneous determination of V(IV) and V(V)
by the proposed system. The absorbances correspond-
ing to V(IV) at 562 nm and at two selected times 60
and 240 s are bi and Ai, respectively, while those cor-
responding to V(V) under the same condition are b
and A . A and b are equal because of the fast kinetics
of complex formation between XO and V(V). They
are related, in the simplest assumption, through the
following equations [17]:
for V(IV) Ai = bi + miti 60 ≤ tj ≤ 240
i = 0, 1, ..., n (1)
for V(V) or interferent A = b + m tj (m = 0) (2)
where the subscripts i and j denote the different solu-
tions for n additions of V(IV) concentration prepared
in order to apply the HPSAM and the time compris-
4. 278 A. Safavi et al. / Analytica Chimica Acta 409 (2000) 275–282
Fig. 2. Effect of pH on the change in absorbance of the XO–V(IV) system in a fixed time (between 30–60 s).
ing the 60–240 s range, respectively. These two times
were selected because the change in absorbance re-
lated to V(V) concentration was negligible in this time
interval and also there was an appropriate difference
between the slopes of the calibration lines for V(IV)
at these two times. Thus, the overall absorbances of
the V(IV)–V(V) mixture at 60 and 240 s are:
at 60 s A60 = bi + b (3)
at 240 s A240 = Ai + A (4)
However, applications of HPSAM at the two
aforesaid times are:
Fig. 3. Kinetic curves for (a) 1.0 g ml−1 V(IV) (b) 1.0 g ml−1 V(V) (c) mixture of 1.0 g ml−1 V(V) and 1.0 g ml−1 V(IV).
A60 = b0 + b + M60Ci (5)
A240 = A0 + A + M240Ci (6)
which intersect at point H(−CH, AH) ≡ (−CV(IV),
AV(V)) (Fig. 4). M60 and M240 are the slopes of the
calibration lines at 60 and 240 s, respectively.
At the intersection point:
b0 + b + M60CH = A0 + A + M240CH (7)
hence
CH = (A − b) +
(A0 − b0)
(M60 − M240)
(8)
5. A. Safavi et al. / Analytica Chimica Acta 409 (2000) 275–282 279
Fig. 4. Plot of H-point standard addition method for simultaneous determination of V(IV) (1.05 g ml−1) and V(V) (1.85 g ml−1).
Table 1
Results of four replicate experiments for the analysis of V(IV)–V(V) mixtures
A–C equation r Present in the sample (g ml−1) Found (g ml−1)
V(IV) V(V) V(IV) V(V)
A240 = 0.304 Ci + 0.520 0.9998 0.62 1.85 0.63 1.82
A60 = 0.192 Ci + 0.451 0.9988
A240 = 0.300 Ci + 0.401 0.9997 0.21 1.85 0.23 1.83
A60 = 0.190 Ci + 0.576 0.9989
A240 = 0.304 Ci + 0.520 0.9998 1.86 0.92 1.76 0.90
A60 = 0.188 Ci + 0.464 0.9999
A240 = 0.300 Ci + 0.317 0.9997 0.74 0.78 0.74 0.73
A60 = 0.188 Ci + 0.234 0.9998
As the V(V) complex is assumed not to evolve over
the considered range of time, then A = b and
CH =
(A0 − b0)
(M60 − M240)
(9)
which is equivalent to the existing CV(IV)(= b0/M60
= A0/M240). So, as shown in Fig. 5(a), the value of
CH is independent of the concentration of V(V) in the
sample.
Substitution of CV(IV) into Eq. (5), yields AH = b.
The overall equation for the absorbance at the H-point
is simply:
A = b = AH = AV(V) (10)
So, again as shown in Fig. 5(b) the value of AH is
independent of the amount of V(IV) in the sample.
Therefore, the intersection of the straight lines by
Eqs. (5) and (6) directly yields the unknown V(IV)
concentration (CV(IV)) and the analytical signal of the
Table 2
Determination of V(IV) in different samples
Sample Concentration of V(IV) (g ml−1)
Spiked Founda
Blood serum 0.50 0.45 ± 0.08
Blood serum 0.75 0.78 ± 0.07
River water 0.50 0.52 ± 0.05
Tap water 0.25 0.27 ± 0.04
Syntheticb 0.25 0.22 ± 0.04
a Mean ± s.d. (n = 5).
b The composition of the synthetic sample was, V(V) 2.5 g
ml−1, Cu(II) 5.1 g ml−1, Cd(II) 40 g ml−1, Pb(II) 12 g ml−1,
Ca(II) 6 g ml−1, Zn(II) 2.0 g ml−1, Na(I) 276 g ml−1.
6. 280 A. Safavi et al. / Analytica Chimica Acta 409 (2000) 275–282
Fig. 5. Plots of H-point standard addition method for (a) fixed V(IV) concentration (1.24 g ml−1) and different concentration of V(V);
(b) fixed V(V) concentration (1.85 g ml−1) and different concentration of V(IV).
V(V) species (AV(V)) corresponding to t60 and t240 in
the original samples, as the two times were chosen in
such a way that the latter species had the same ab-
sorbance at both times. This analytical signal enables
the calculation of the concentration of V(V) from a
calibration graph. Several synthetic samples with a
different concentration ratio of V(IV) and V(V) were
analyzed by HPSAM . As can be seen from Table 1,
the accuracy of the results is satisfactory in all cases.
In addition, for the validation of the method, environ-
mental and biological complex matrix samples were
spiked with V(IV) and the proposed method was ap-
plied for determination of the analyte. The results are
shown in Table 2; it can be seen that the results are
satisfactory.
An absorbance increment as an analytical signal can
be employed in another version of HPSAM to allow
the analyte concentration, CV(IV), to be calculated with
no systematic, constant or proportional error thanks to
the intrinsic feature of the HPSAM and the nature of
7. A. Safavi et al. / Analytica Chimica Acta 409 (2000) 275–282 281
Fig. 6. A vs. added V(IV) concentration at different time intervals and 562 nm for synthetic mixtures with (a) 0.77 g ml−1 V(IV) and
0.74 g ml−1 V(V) (b) 1.53 g ml−1 V(IV) and 2.50 g ml−1 V(V).
Table 3
Application of signal increment version of HPSAM to two synthetic mixtures
Time interval (s)
100–240 150–240 100–150 100–200 80–200 60–240 60–200 90–150 110–170 80–200
V(IV) Found (g ml−1) 0.73 0.71 0.71 0.76 0.70 1.57 1.57 1.54 1.57 1.56
Actual V(IV) (g ml−1) 0.77 1.53
Relative standard deviation (%) 2.6 (n = 5) 0.6 (n = 5)
8. 282 A. Safavi et al. / Analytica Chimica Acta 409 (2000) 275–282
the method of standard addition. This variant should
be of use whenever only the analyte is to be deter-
mined or when the A–t curve rather than the compo-
sition of the matrix is known. It should also be useful
to apply the single-standard calibration method, which
features greater simplicity and rapidity. This method
can also be used to diagnose the occurrence of inter-
ferences with a given analytical procedure as, in the
absence of errors, the plot of any At1−t2 against the
added analyte concentration will have a constant point
(−CH, 0) [17]. Thus, for the determination of V(IV)
in the presence of V(V), the absorbance increment
as an analytical signal was used. The application of
the HPSAM in the At1−t2 –Cadded variant yields the
concentration of V(IV) directly from the intercept on
the y-axis. However, in order to ensure the absence
of constant and proportional errors from the calcu-
lated concentration, all the possible At1−t2 –Cadded
lines for V(IV) should intersect at the same point,
namely, that corresponding to the unknown concen-
tration, CH, as this would indicate that the time eval-
uation of the matrix would be a horizontal line. Fig.
6 and Table 3 show the results obtained from em-
ploying this version of HPSAM on the synthetic mix-
tures of V(IV) and V(V). The results obtained by this
procedure were in good agreement with those given
above.
The behavior of the system in the presence of some
ions was also studied. As (III), Cd2+, Sn (II), Pb2+,
Ca2+, Na+ and K+ did not complex with XO un-
der working conditions and thus up to 100 g ml−1
of these ions did not interfere with the determination
of 0.50 g ml−1 V(IV). Cu2+, Hg2+, Zn2+, Mg2+,
Co2+, Se(IV), Te(IV) and Fe3+ instantly form com-
plexes with concentrations up to g ml−1 level, and
because complex formation is fast, no interference was
observed from their presence in the determination of
V(IV). However, only Al3+, Ni2+ and Fe2+ showed
an interference, due to slow complex formation at the
g ml−1 level.
Acknowledgements
The authors gratefully acknowledge the support of
this work by the National Research Council of I.R.
Iran (NRCI) as a National Research Project under the
grant number 1081.
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