X-RAY FLUORESCENCE SPECTROSCOPY

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X-RAY FLUORESCENCE SPECTROSCOPY:

N. Sandhya Rani, 11AB1S0418, M.Pharm(PA&QA ) X-RAY FLUORESCENCE SPECTROSCOPY

CONTENTS::

CONTENTS : PRINCIPLE BRAGG’S LAW INSTRUMENTATION TYPES APPLICATIONS

PRINCIPLE::

PRINCIPLE:

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Emitted bandwidth is characteristic of elements and enables us to identify the element. Fluorescent intensity is the function of concentration of sample. For qualitative studies, the angle of diffraction, Ø is measured. F rom this wavelength of fluorescence can be calculated using Bragg’s equation.

BRAGG’S LAW::

BRAGG’S LAW:

INSTRUMENTATION::

INSTRUMENTATION: X-RAY SOURCE SAMPLE HOLDERS ANALYSING CRYSTALS DETECTORS

X-RAY SOURCE::

X-RAY SOURCE: Intensity must be high, for this voltage should be as high as 100kv. Wavelength of radiation must be 16% of the minimum wavelength required to excite the sample. The standard X-ray tube was developed by Coolidge around 1912.

SAMPLE HOLDERS::

SAMPLE HOLDERS: Materials shouldn’t absorb x-ray beams hence polymers such as polyethylene is used. Aluminum holders Dispoza-cups 1A. Cell made up of cellulose acetate butyrate 1B. Nitrile O-rings are fixed 1C. Micro porous film made of polypropylene

SAMPLE PREPARATION::

SAMPLE PREPARATION: Solid samples: Liquid samples: Most satisfactory as they flow easily in to holders with flat surfaces. Best solvents are water, nitric acid, hydrocarbons and oxygenated carbon compounds as they contain low atomic number .

MONOCHROMATOR::

MONOCHROMATOR: Analyzing crystal acts with x-rays in same way as grating chromator with visible light. The crystal separates x-rays of different wavelengths by diffracting them at different angles. a)flat monochromator crystals b)curved monochromator crystals Ideal character --- d should be constant. Curved crystals are made up of Sodium chloride Lithium fluoride Quartz Aluminium Topaz Ammoniumdihydrogen orthophosphate

DETECTORS::

DETECTORS: Used to measure and record x-ray intensities. Types: Gas proportional counter Scintillation counter Geiger-Muller tube counter Semi-conductor detectors Germanium detectors Silicon drift detectors

GAS PROPORTIONAL COUNTER::

GAS PROPORTIONAL COUNTER: Filled with P90 gas (90% argon, 10% methane). X-rays ionize the gas, leaving electrons that migrate to the anode and positive ions that move to the cathode. Proportional counters use gas amplification. The primary electrons and ions, first formed, are accelerated to produce secondary electrons and ions. This yields a greatly increased signal which is, nevertheless, proportional to the energy of the original x-ray.

TYPES::

TYPES: 1) Wavelength dispersive XRF spectrophotometers (WDXRF) a) using flat crystal b) using curved crystal 2) Energy dispersive XRF spectrophotometers (EDXRF)

WDXRF: (flat crystal):

WDXRF: (flat crystal)

WDXRF: (curved crystal):

WDXRF: (curved crystal)

EDXRF::

EDXRF:

COMPARISION between WDXRF and EDXRF:

COMPARISION between WDXRF and EDXRF Resolution Reduced spectral overlap Elements with close atomic number

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HANDHELD ( X-DELTA ) PORTABLE (INNOV-XX-50) BENCHTOP/LABMODEL ( ARL QUANT’X )

XRF SPECTRA LINES: :

XRF SPECTRA LINES: ORIGIN OF DIFFERENT LINES IN XRD SPECTRA: K SERIES L SERIES M SERIES…..

SIMPLE XRF SPECTRA::

SIMPLE XRF SPECTRA: XRF spectra of arsenic containing compound

QUANTITATIVE ANALYSIS::

QUANTITATIVE ANALYSIS:

MATRIX EFFECTS::

MATRIX EFFECTS: The absorption of primary radiation and absorption and enhancement of fluoresced characteristic lines is termed matrix effects. In XRF absorption-enhancement effects arise from the following phenomena: 1.primary-absorption effect 2.secondary-absorption effect 3.enhancement Matrix effect is often negligible when thin samples are used for analysis.

APPLICATIONS::

APPLICATIONS: heavy-metal determination of drugs and excipients in the pharmaceutical industry. multi-elemental analysis determination of essential trace elements (e.g., Fe, Cu, Zn, Cr, Se, Ca , Mg, Co, Mo, I, Si, and Mn ), as well as toxic elements (Cd, Mo, Pb , Hg, As, and Sn ) P harmacy :

MEDICINE::

MEDICINE: determination of sulphur in protein determination of chlorides in blood serum, strontium in blood serum and bone tissue Elemental analysis of tissues, bones, body fluids

MINING::

MINING: Direct analysis of drill core and cuttings Elements of hydrothermal origin can be analysed Analysis of raw materials for determining penalty elements in coal (Fe), Fe ore, bauxite, limestone Light element and trace metal analysis for gas shale and mud logging applications.

AGRICULTURE::

AGRICULTURE: Heavy metal contamination of vegetables Phosphorous in fertilizers Insecticides on fruits and leaves Several elements such as K, Ca , Ti, Mn , Fe, Cu, Zn, Br at ppm levels

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Analyzing non-corrosive metals, alloys and geological materials. Determination of Element Alloys lead Lead-tin alloy Chromium Stainless steel Manganese Plain steel Copper, zinc, tin Copper alloy Tin, zinc Galvanized steel

CEMENT INDUSTRY::

CEMENT INDUSTRY: Elemental analysis of free lime and key clinker phases Helps to adjust parameters that stabilize calcination and clinkerisation process

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ENVIRONMENTAL STUDIES: Metals dispersed in soil in and around mining and urban areas can be easily resolved. PETROLEUM INDUSTRY: Sulfur levels in gasoline Total chlorine in petroleum products Metals in lubricating oils RUBBER INDUSTRY: Vulcanizing element can be determined

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SPACE TECHNOLOGY: Analysis of new alloys and ceramics DENTISTRY: Ca , P, Na, Mg, Al, S, K in teeth samples can be determined GLASS INDUSTRY: Process control of glass during manufacture. Elemental ratios of small glass fragments Ti/ Sr , Mn / Sr

STRENGHTS::

STRENGHTS: Bulk chemical analysis of major elements ( Si, Ti, Al, Mn , Mg, Ca , Na, K, P ) Analysis of trace elements ( >1ppm ),(Ba, Ce , Cu, Co, Cr, La, Ni, Rb , Sr , U, V, Zr ) Simple spectra Spectral positions are almost independent of the chemical state of the analyte Minimal sample preparation It is non-destructive Applicable over a wide range of concentrations Good precision and accuracy

LIMITATIONS::

LIMITATIONS: Elements with atomic number less than 11 ( Z<11) cannot be measured. Inter element (MATRIX) effects may be substantial and require computer correction Limits of detection are only modest Instrumentation is fairly expensive

CONCLUSION::

CONCLUSION: With the help of both wavelength-dispersive (WDXRF) and energy-dispersive (EDXRF) x-ray fluorescence spectrometers virtually all types of sample materials can be analysed . Higher degrees of analytical accuracy and precision and lower limits of detection and concentration levels can be done. Hence x-ray fluorescence is now recognized as a versatile laboratory tool useful for both infrequent and routine sample analysis.

REFERENCES::

REFERENCES: Instrumental analysis. Skoog , Holler, Couch pg.no:359-367. Instrumental methods of analysis, 7 th edition, Willard, Merritt, Dean, Settle pg.no:367-372. Introduction to instrumental analysis, Robert. D. Braun. Pg.no:570-575. Instrumental methods of chemical analysis, Gurdeep R. Chatwal , Sham K. Anand . Pg.no:2.332-2.338 Serc.carleton.edu/research-education/techniques/XRF www.icdd.com www.ncbi.nlm.nih.gov www.gac-cs.ca

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