ICP AES overview-Nipa 25.01.2023.pptx
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Estimation of heavy metals and trace elements by inductively couple plasma-atomic emission spectrometer
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ICP AES overview-Nipa 25.01.2023.pptx
- 1. QUANTITATIVE ESTIMATION OF TRACE ELEMENTS BY INDUCTIVELY COUPLED PLASMA- ATOMIC EMISSION SPECTROSCOPY( ICP-AES) Presenter Dr. Nipa Mendapara Junior Resident Department of Pharmacology AIIMS New Delhi
- 2. ICP-AES USE: • Used for the determination of ppm levels of metals in liquid samples • It is widely used to analyze liquid samples as well as substances that are easily dissolved or digested into liquid form • Common sample types analyzed by ICP include trace elements in polymers, wear metals in oils, and numerous catalysts 2
- 4. Clinical importance of trace elements • Essential trace elements are usually associated with an enzyme (metalloenzyme) or protein (metalloprotein) as an essential component or cofactor. 1. Deficiencies typically impair one or more biochemical functions 2. Excess concentrations are associated with at least some degree of toxicity. 4
- 5. Photon Energy Absorbed Energy Emitted Atomic Absorption Spectrometer Atomic Emission Spectrometer E=hc/λ Why does the elements emit or absorb a specific radiation? 5
- 6. Atomic Absorption Light of specific wavelength from Hollow Cathode Lamp (HCL) Atomic Emission Light and heat energy from high intensity source (flame or plasma) Mass Spectrometry Light and heat energy from high intensity source (plasma) Light of specific characteristic wavelength is absorbed by promoting an electron to a higher energy level (excitation) Light absorbed is proportional to elemental concentration High energy (light and heat) promotes an electron to a higher energy level (excitation). Electron falls back and emits light at characteristic wavelength. Light emission is proportional to elemental concentration High energy (light and heat) ejects electron from shell (ionization). Result is free electron and atom with positive charge (ion) Ions are extracted and measured directly in mass spectrometer METHODS 6
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- 9. WHICH METHOD TO USE AND WHEN? AAS MS 9
- 10. ICP-Mass spectrometry (MS) •It has multi-element capability •Liquid samples are first nebulized in the sample introduction system, creating a fine aerosol that is subsequently transferred to the argon plasma •High-temperature plasma atomizes and ionizes the sample, generating ions which are then extracted through the interface region and into a set of electrostatic lenses called the ion optics. 10
- 11. Continue.. •The ion optics focuses and guides the ion beam into the quadrupole mass analyzer. •The mass analyzer separates ions according to their mass-charge ratio (m/z), and these ions are measured at the detector. 11
- 12. ICP-MS 12
- 13. Difference between AES and MS ICP-AES • Provides higher detection limit down to ppm or ppb • Detects energy (photons) emitted by the atoms • Isotopes compositions can not be detected • Less costly compared to MS ICP-MS • Provides a lower detection limit down to ppt (ng/l) (highly sensitive) • Able to detect the ions. Then, these ions are sorted on account of their mass. • Possibilities to detect isotope composition of elements i.e. 2H/1H, 13C/12C • Disadvantages is the occurrence of spectral and non-spectral interferences and the high costs. 13
- 14. ICP-AES 14
- 15. •ICP-AES for the estimation of heavy metals •Model: JY 2000-2 •Company: Horiba Jobin Yvon ICP-AES 15
- 16. ATOMIC EMISSION SPECTROPHOTOMETER • The fundamental characteristic of this process is that each element emits energy at specific wavelength peculiar to its atomic structure. • The energy transfer for electron when they fall back to ground state is unique to each element as it depends on the electronic configuration of the orbital. • The energy transfer is inversely proportional to wavelength of electromagnetic radiation E= hc/n where h is plank’s constant; c is velocity of light and n is the wavelength. Hence, the wavelength of light emitted is also unique! 16
- 17. Principle Inductively Coupled Plasma- Atomic Emission Spectrometer Atoms of samples are excited by plasma at very high temperature (100000K) Return to the normal states, emit characteristic photons of energy Electrons of an atom absorb energy and jump to higher energy levels 17
- 18. PLASMA- It is a conducting gaseous mixture containing a significant concentration of ions and electrons. • Argon Plasma is commonly used. • The temperature of the plasma may be of the order of 5,000 to 10,000 K. 18
- 19. Working flow of ICP-AES 19
- 20. 7. As the excited atoms reach the detector they again decay to ground state and emitting a photon 8. This photon is amplified and captured by the detector with charge coupled device (CCD) 1. Plasma Gas flows into the ICP Torch 2. Radiofrequency (RF) Generator coil induces Electromagnetic Potential (40.68 MHz) 3. Ionization of Argon Ar ------> Ar+ & e- 4. Resistance of e- to move with the circular magnetic field causes intense heat and generation of Plasma 5. Injection of sample element through the nebulizer 6. Atoms leave the flame towards detector (Axial or Radial) in a excited state 20
- 21. Components of ICP-AES 1. Sample introduction system 2. Radiofrequency generator 3. Optical system 4. Signal processing system 5. Computer system Inductively coupled plasma source Separation and detection 21
- 22. 1. Sample Introduction System: • Liquid samples are pumped into the nebulizer and sample chamber via a peristaltic pump. • Then the samples pass through a nebulizer that creates a fine mist of liquid particles. • Larger water droplets condense on the sides of the spray chamber and are removed via the drain, while finer water droplets move with the argon flow and enter the plasma. • Nebulizers help ensure that the sample enters into the plasma at a uniform flow rate and specific droplet size. • Droplets that are great than 5 µm in diameter are likely to interfere with plasma stability. 22
- 23. 2. Radiofrequency Generator: • Creates an oscillating magnetic field around the torch that results in ohmic (inductive) heating of the charged gases at the end of the torch: Sustains plasma • Solid-state semiconductor generators (commonly used), where circuit consists of a) Capacitor: Stores a high electrical charge (thus requiring the 220-240 V electrical power requirements) a) Inductor coil: Deliver the oscillating current to the torch and generate the magnetic field around the torch 23
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- 25. Torch • The plasma is formed in the end of a set of three concentric quartz tubes, collectively referred to as the torch • Argon gas flows through all three tubes 1. The inner tube is called the injector, and contains the sample aerosol in a stream of argon which delivers the sample to the plasma 2. Concentric to this tube is a tangential flow of argon called the auxiliary gas, which forms the plasma 3. The outer tube contains a flow of argon which serves as a cooling layer to prevent the torch from melting 25
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- 27. Plasma: Partially ionized gas which is electrically neutral (cations and electrons) 27
- 28. View of the detection • Depending on the concentration of analytes in a given sample, the analyst may choose to monitor the emissions from the a) Radial view: for higher concentrations b) Axial view: for lower concentration 28
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- 30. Types of spectrometers • Three categories of detection are available for analysing the emitted photons: 1. Sequential 2. Simultaneous multi-channel 3. Fourier transform systems 30
- 31. In both, all wavelengths enter a monochromator where they are dispersed by prisms and/or grating monochromators and are then transmitted to the detector SEQUENTIAL SIMULTANEOUS MULTI-CHANNEL 31
- 32. Types of spectrometers 1. Sequential : less expensive and more flexible • They include a single photomultiplier tube and movable gratings to select wavelength in sequential orders 2. Direct/simultaneous: faster, more precise, and more accurate • All elements (up to 60) are determined simultaneously by increasing the analytical speed • Radiations from the plasma enter through single slits and are dispersed by a concave reflection grating • Then these wavelengths reach a series of exit slits which isolate specific wavelengths for specific elements https://psiberg.com/atomic-emission-spectroscopy/ 32
- 33. Fourier transform systems • No slits or monochromators are required, and this creates better detector limits because more intense radiation reaches the detector. • Fourier transform systems also have higher spectral resolution (and thus have fewer spectral interferences) and can simultaneous monitor all wavelengths for longer times. 33
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- 39. Research studies undertaken in our Department 39
- 40. Other Examples of ICP AES studies • S S, Ss A, S SB, Hk V, Pv M. Determination of the bioavailability of zinc oxide nanoparticles using ICP- AES and associated toxicity. Colloids Surf B Biointerfaces. 2020 Apr;188:110767. • Zhang Y, Ge S, Yang Z, Dong C. Heavy metals analysis in chalk sticks based on ICP-AES and their associated health risk. Environ Sci Pollut Res Int. 2020 Oct;27(30):37887-37893. • Reproductive toxicity of lead, cadmium and phthalate exposure in men. Pant N, Kumar G, Upadhyay AD, Patel DK, Gupta YK, Chaturvedi PK. Environ Sci Pollut Res Int. 2014 Sep;21(18):11066-74 • Monitoring of mercury, arsenic, cadmium and lead in Ayurvedic formulations marketed in Delhi by flame AAS and confirmation by ICP-MC. Kumar G, Gupta YK.Food Addit Contam Part B Surveill. 2012;5(2):140-4. • Semen quality of environmentally exposed human population: the toxicological consequence. Pant N, Pant AB, Chaturvedi PK, Shukla M, Mathur N, Gupta YK, Saxena DK. Environ Sci Pollut Res Int. 2013 Nov;20(11):8274-81 • Dark colored semen in non obstructive azoospermia: a report of four cases. Halder A, Jain M, Chaudhary I, Kumar G, Das T, Gupta YK. Andrologia. 2014 Apr;46(3):316-21 40
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Editor's Notes
- Trace elements found in PPM (mg/L) or less than PPB (µg/L).
- Examples of conditions that could result in deficiency of trace elements: Decreased intake, Impaired absorption, Increased excretion, And genetic abnormalities copper deficiency are seen in Menkes' disease Too much copper in the diet can result in damage to the liver, discoloration of the skin and hair, and can cause hyperactivity in children. Too much iron in the diet can result in damage to the heart and liver. Zinc is a component of certain digestive enzymes and other proteins. Not enough in the diet can result in growth failure, scaly skin inflammation, reproductive failure and impaired immunity. People who suffer from iron deficiency show symptoms such as lack of energy, getting tired easily and being short of breath.
- Study of electromagnetic radiation absorbed and emitted by atoms
- It mostly depends on purpose and budget.
- The role of the ion optics system is to guide the ion beam toward the mass analyser, and to prevent photons and other neutral species (such as non-ionised matrix components) from reaching the detector. By far the most common type used for routine clinical biochemistry applications is the quadrupole mass analyser. essentially a mass filter, separating ions based on their m/z ratio (defined as the mass of an ion divided by its charge). quadrupole consists of four parallel hyperbolic or cylindrical metallic rods (normally 15–20 cm long) positioned in a square array. Radio frequency alternating current (AC) and direct current (DC) potentials are applied to the rods, creating a time-varying electric field in the centre through which ions pass. Positively-charged analyte ions strike the first dynode of the detector which is held at a high negative voltage. The impact of the ion on the detector causes the emission of several electrons from the surface, which, in turn, strike the next dynode releasing more electrons. This process (called secondary emission) continues, generating an amplification cascade that culminates in a signal large enough to be measured reliably as an ion ‘count’. In this way, an EM can generate a measurable signal pulse from the impact of a single ion on the detector, conferring very high analytical sensitivity.
- This is a type of emission spectroscopy that uses the inductively coupled plasma to produce excited atoms and ions that emit EMR at wavelength characteristic to a particular element
- Argon is inert gas which doesn’t react with other metals
- At the end of the tube, larger aerosol droplets exit the spray chamber under the influence of gravity and are drained to waste while smaller droplets, roughly <10 μm diameter, are transferred to the plasma. This is important because the plasma is inefficient at dissociating large droplets (>10 μm diameter). Nebulizer (derived from nebula): converting liquid to fine spray “Pneumatic” use air or a similar gas for nebulization (most popular types: concentric, fixed cross-flow, and high solids) “Ultrasonic” use sound instead of a gas as the energy source for converting a liquid to a mist (Instrument in our department has cross-flow pneumatic nebulizer)
- The capacitor responsible for generating the plasma from argon gas, oscillates an electrical field at a rate between approximately 27 and 41 MHz (a frequency regulated by the FCC) and through induction creates a magnetic field in the plasma. The intensity of the frequency, measured in Watts, is sufficient to promote the valance electrons in some of the Ar atoms but not ionize them sufficiently to initiate or sustain a plasma.
- The torch is cooled in two ways, the first is by the tangential introduction of relatively large volumes of argon gas through the outer tube of the torch. This argon flow spirals around the middle tube resulting in uniform cooling. Furthermore cooled water flows through the copper induction coil of the RF generator that is wrapped around the end of the torch. These combined cooling systems promote an equilibrium maximum temperature of approximately 10 000 K in the hottest portion of the plasma.
- The purpose of the plasma torch is to (1) evaporate the solvent (usually water) from the analyte salts, (2) atomize the atoms in the salt (break the ionic bonds and form gaseous state atoms), and (3) excite or ionize the atoms. A plasma is an electrically conducting gaseous mixture containing enough cations and electrons (though the plasma has a neutral charge overall) to maintain the conductance. The creation of plasma occurs when a spark (from a Tesla coil; basically an automatic gas grill lighter) introduces free electrons at the end of the torch when the electrical field is being oscillated at a specific frequency by a RF generator. The seed electrons from the Tesla coil oscillate in an angular path and periodically collide with argon gas atoms and ionize them, releasing more electrons. Due to their kinetic energy and collisions with other atoms a large amount of heat is generated, enough to generate and sustain a plasma at temperatures up to 10 000 K. In terms of an electrical analogy, the term “inductively coupled” in ICP is a result of the coupling of the induction coil and the electrons. The copper induction coil serves as the “primary winding” of the radiofrequency transformer and the “secondary winding” is the oscillating electrons and cations in the plasma; the two “windings” are thus coupled together because the second winding depends on the presence of the first. Both atoms and ions becomes excited in the plasma and they revert to their ground state in tail flame, they emit light (photon).
- TDS- total dissolved solids
- Photomultiplier tubes, photoemissive cells, or array detectors act as detectors. They are used to convert optical signals into electrical current which is then amplified by the amplifier.
- Separation of spectral lines can be accomplished in two ways. In a sequential or scanning ICP, a scanning monochromator with a movable grating is used to being the light from the wavelength of interest to a single detector. In a simultaneous or direct reader ICP, a polychromator with a diffraction grating is used to disperse the light into its component wavelength.