Quantification of Mineral Nutrients Using Advanced Instruments Like AAS & ICP
- 1. Quantification of Mineral Nutrients Using Advanced Instruments Like AAS & ICP Presented by :- S. A. Patil A. S. Deshmukh Ph.D Scholar Department of Agriculture Botany, VNMKV, Parbhani Course No. PP-604 Vasantrao Naik Marathwada Krishi Vidyapeeth, Parbhani College of Agriculture, Parbhani
- 2. 1) AAS (Atomoic Absorption Spectorometry) 2) ICP (Inductively Coupled Plasma) Advance Instruments for Quantification of Mineral Nutrients
- 4. Introduction Atomic Absorption Spectrometry (AAS) INDEX Introduction Importance Principle of AAS Instrumentation Applications Limitations
- 5. Introduction Atomic Absorption Spectroscopy (AAS) is also famous by the name Atomic Emission Spectroscopy (AES). AAS is a spectroanalytical procedure for the quantitative determination of chemical elements using the absorption of optical radiation (light) by free atoms in the gaseous state. AAS can be used to determine over 70 different elements. It is very reliable and simple to use.
- 6. HISTORY The phenomenon of Atomic Absorption (AA) was first observed in 1802 with the discovery of the Fraunhofer lines in the sun's spectrum. Fraunhofer lines, in astronomical spectroscopy, any of the dark (absorption) lines in the spectrum of the Sun or other star, caused by selective absorption of the Sun's or star's radiation at specific wavelengths by the various elements existing as gases in its atmosphere. It was not until 1953 that Australian physicist Sir Alan Walsh demonstrated that Atomic Absorption could be used as a quantitative analytical tool.
- 7. Cont…..
- 8. What is Atomic Absorption Spectrometry? AAS detects elements in either liquid or solid samples through the application of characteristic wavelengths of electromagnetic radiation from a light source. Individual elements will absorb wavelengths differently, and these absorbances are measured against standards. In effect, AAS takes advantage of the different radiation wavelengths that are absorbed by different atoms. In AAS, analytes are first atomized so that their characteristic wavelengths are emitted and recorded. Then, during excitation, electrons move up one energy level in their respective atoms (figure 1) when those atoms absorb a specific energy. As electrons return to their original energy state, they emit energy in the form of light (figure 2). This light has a wavelength that is characteristic of the element. Depending on the light wavelength and its intensity, specific elements can be detected and their concentrations measured.
- 9. Importance of AAS & ICP Instruments in Plant Physiology Plant requires at least sixteen elements for normal growth and completion of their life cycle. These elements occur in very small amounts in both soil and plants, but their role is as important. A deficiency of one or more of the micronutrients can lead to severe depression in growth, yield, and crop quality. Some soils do not contain sufficient amounts of these nutrients to meet the plant’s requirement for rapid growth and good production. In this case, supplemental micronutrients for rapid growth and good yield have to be applied in the form of foliar sprays with adequate knowledge of the elemental concentrations. Thus this work seeks to analyze the essential elements for plants growth by using instrumental neutron activation analysis.
- 10. Principle of AAS The sample form of a homogeneous liquid is aspirated in to flame where “free” atoms of the element to be analysed are created. A light source (hollow cathode lamp) is used to excite the free atoms formed in the flame by the absorption of the electromagnetic radiation. The decrease in energy (absorption) is then measured which follows the Lamber-beer’s law, i.e. the absorbance is proportional to the number of free atoms in the ground state. Lamber-beer’s law The absorbance of light is proportional to the thickness of the sample or The absorbance is proportional to the concentration of the sample.
- 13. Instrumentation
- 15. LIGHT SOURCE Hollow Cathode Lamp are the most common radiation source in AAS. It contains a tungsten anode and a hollow cylindrical cathode made of the element to be determined. These are sealed in a glass tube filled with an inert gas (neon or argon) Each element has its own unique lamp which must be used for that analysis.
- 16. NEBULIZER Suck up liquid samples at controlled rate. Create a fine aerosol spray for introduction into flame. Mix the aerosol and fuel and oxidant thoroughly for introduction into flame. ATOMIZER Elements to be analysed needs to be in atomic state. Atomization is a separation of particles into individual molecules and breaking molecules into atoms. This is done by exposing the analyte to high temperatures in a flame. Atomizers are of two types.
- 18. FLAME ATOMIZER To Create flame, we need to mix an oxidant gas and a fuel gas. In most of the cases air-acetylene flame or nitrous oxide-acetylene flame is used. Liquid or dissolved samples are typically used with flame atomizer. GRAPHITE TUBE ATOMIZER Uses a graphite coated furnace to vaporize the sample. In GFAAS , samples are deposited in a small graphite coated tube which can then be heated to vaporize and atomize the analyte. The graphite tubes are heated using a high current power supply.
- 19. MONOCHROMATOR This is a very important part in an AA Spectrometer. It is used to separate out all of the thousands of lines. A Monochromator is used to select the specific wavelength of light which is absorbed by the sample and to exclude other wavelengths. The selection of the specific light allows the determination of the specific element in the presence of others.
- 20. DETECTOR The light selected by the monochromator is directed onto a detector that is typically a photomultiplier tube, whose function is to convert the light signal into an electrical signal proportional to the light intensity. The processing of electrical signal is fulfilled by a signal amplifier. The signal could be displayed for readout or further fed into a data station for printout by the requested format.
- 21. Calibration Curve A Calibration curve is used to determine the unknown concentration of an element in a solution. The instrument is calibrated using several solutions of known concentrations. The absorbance of each known solution is measured and then a calibration curve of concentration vs. absorbance is plotted. The sample solution is fed into the instrument and the absorbance of the element in this solution is measured. The unknown concentration of the element is then calculated from the calibration curve.
- 22. Applications (AAS) Quantitative analysis can be done using Calibration Curve Method. Very low concentration which is 1 ppm or less than that can also be analysed accurately with the help of AAS. With the help of AAS can detect the toxic elements such as Cu, Ni, Zn present in the food products. How much amount of Pb (lead) is present in the Petrol can be found out with the help of AAS. Soil extracts, plant materials, fertilizers have been analysed for determination of Na, K, Cu, Mg, Mo, V etc. are present. The amount of Ti and V present in the steel alloy can also be determined with the help of AAS.
- 23. Limitations Non metal elements not be determined directly by atomic absorption spectroscope because of it's high Ionization Enthalpy. Simultaneous analysis of many elements is not possible. Metals like La, W, Si. etc. form the stable metallic oxide and so cannot be analysed. For alkali metals like Li, Na, K etc. which has low I.P. in such cases low temperature of the flame is required to minimize the ionization of the elements. Each element requires the separate lamp. If the sample contains the two elements which absorb the light of same Wavelength. (λ) Mn and Ga both absorb at 403nm can not be analysed. In such case we must remove the interfering radical.
- 25. ATOMIC SPECTROSCOPY INDUCTIVELY COUPLED PLASMA (ICP) INDEX Introduction Importance Principle of ICP Instrumentation Applications Limitations
- 26. Introduction It has been 25 years since ICP optical emission spectrometers began to be widely used, and is now one of the most versatile methods of inorganic analysis. Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), also referred to as Inductively Coupled Plasma Optical Emission Spectrometry (ICP- OES) It is an analytical technique used for the detection of chemical elements.
- 27. Importance of AAS & ICP Instruments in Plant Physiology Plant requires at least sixteen elements for normal growth and completion of their life cycle. These elements occur in very small amounts in both soil and plants, but their role is as important. A deficiency of one or more of the micronutrients can lead to severe depression in growth, yield, and crop quality. Some soils do not contain sufficient amounts of these nutrients to meet the plant’s requirement for rapid growth and good production. In this case, supplemental micronutrients for rapid growth and good yield have to be applied in the form of foliar sprays with adequate knowledge of the elemental concentrations. Thus this work seeks to analyze the essential elements for plants growth by using instrumental neutron activation analysis.
- 28. Why is called as ICP ? Insulating solid samples are placed near the discharge so that ionized gas atoms sputter the sample into the gas phase where the analyte atoms are excited. This sputtering process is often referred to as glow-discharge excitation.
- 29. Principle of ICP As indicated by its name, Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES or ICP-AES) is a technique that uses a plasma as a source and relies on optical emission for analysis. However, unlike many other spectrometers, the sample is not simply placed in-between source and detector.
- 31. Mechanism of ICP ICP, abbreviation for inductively coupled plasma is one method of optical emission spectrometry. When plasma energy is given to an analysis sample from outside, the component elements (atoms) are excited. When the excited atoms return to low energy position, emission rays (spectrum rays) are released and the emission rays that correspond to the photon wavelength are measured. The element type is determined based on the position of the photon rays, and the content of each element is determined based on the rays intensity. To generate plasma, first argon gas is supplied to torch coil, and high frequency electric current is applied to the work coil at the tip of the torch tube. Using the electromagnetic field created in torch tube by the high frequency current, argon gas is ionized and plasma is generated. This plasma has high electron density and temperature (10000k) and this energy is used in the excitation emission of the sample. Solution samples are introduced in to the plasma in an automized state through the narrow tube in the center of the torch tube.
- 33. Instrumentation ICP COMPONENTS 1. Sample introduction unit: Convert sample solution into aerosol (Peristatic pump, nebulizer and spray chamber). 2. Energy source: Plasma convert aerosol into energized atoms (Radio frequency generator, load coil and torch) 3. Spectrometer: (Diffract white light into wavelength) 4. Detector: (Measure intensity of wavelength) 5. Output unit: Computer and software
- 34. Sample preparation Minimum 5ml of standards or samples are used. Samples should be filtered with 0.45μm filter. 2 % by volume (HNO3) is added to samples and standards. For testing Bromide or Iodide 0.1 % ammonium hydroxide added.
- 35. ICP discharge (Energy unit) Spark cause electrons to be stripped from argon atoms Electrons are then caught up by magnetic field and accelerated by inductive coil (Inductive coupling) High energy electrons continue collision ionization with argon gas till gas break down into plasma of argon atoms, electrons and ions (Inductively Coupled Plasma)
- 37. Applications (ICP) Very high temperature (6000k) allows for full sample dissociation. Simultaneous, sequential analysis of multiple elements possible. Elements that are difficult to analyze in atomic absorption spectrometry such as Zr, Ta, rare earth, P and B can be easily analyzed. Efficient formation of excited state. Argon inert environment prolongs analyte atoms lifetime. Analyse trace components with accuracy, precision and non-interfering detection limits. (detection limit 1 to 10 ppb). Plasma source has a high degree stability and low interference. Clinical Analysis: Metals in biological fluids (blood, urine). Environmental Analysis: Trace metals and other elements in waters, soils, plants, composts and sludges. Pharmaceuticals: Traces of catalysts used, traces of poison metals (Cd, Pb etc.). Industry: Trace metal analysis in raw materials, noble metals determination. Forensic science: Gun shot powder residue analysis, toxicological examination (eg. Thallium (TI) determination.
- 39. Limitations The disadvantages are the overall inefficiency of the nebulizer and the plasma's sensitivity to organic solvents. The poor tolerance of the plasma source to common mobile phases, such as ion-pair reagents.