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Laser Induced breakdown spectroscopy in Water for elemental analysis. Satyanarayan Ray Pitambar Mohapatra Project Guide: Dr. R.K. Thareja. Advantages of LIBS technique. Can be used for rapid and remote analysis. Real time analysis possible. Complete elemental coverage can be achieved.
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Laser Induced breakdown spectroscopy in Water for elemental analysis. Satyanarayan Ray Pitambar Mohapatra Project Guide: Dr. R.K. Thareja
Advantages of LIBS technique • Can be used for rapid and remote analysis. • Real time analysis possible. • Complete elemental coverage can be achieved. • The analysis spot size is small. • Relatively low detection limit ( ppm/ppb).
Possible application • Detection of elements in nuclear reactors. • Detection of elements inside deep sea. • Space mission; detection of elements in other planets. • Environmental monitoring (soil contamination, particulates) . • Materials analysis (metals, plastics). • Forensics and biomedical studies (teeth, bones analysis). • Military and safety needs (explosive particles, chemical and biological warfare agents e.g. Anthrax). • Art restoration/conservation (pigments, precious/ancient metals).
LIBS on Mars ! • A 300 mJ laser pulse can detect from 25m away. • A 2 J laser pulse can detect from 100m away. photo credit: Chemistry Division , Los Alamos National Laboratory
Setup specification • Wavelength of laser radiation = 355 nm • Energy of laser radiation = 18 mJ • Focal length of Plano-convex quartz lens = 10 cm • Pulse repetition rate = 10 Hz • Gate width for time integrated spectra = 2 micro second • Gate width for time- resolved spectra = 500 ns • Gate delay with respect to laser pulse = 300 ns
Advantages of water based test samples • Relatively low conc. Solution (ppm) can be prepared. • Solution in water are more homogeneous than solid ( so spatial variation of concentration is not there).
Why Na ? • Easily available element to start with. • To determine the concentration of Na in sea ice. • Na concentration in blood and cells.
Typical sodium lines time integrated • Na I 589 nm ( 3s 2S-3p 2P0)( J = 1) D1 line • Na I 589.6 nm ( 3s 2S-3p 2P0)( J = 0) D2 line
Time resolved observation for concentration = 102 ppm, gate delay = 300 ns
Time resolved data of Sodium line for Concentration = 409 ppm, gate delay = 300 ns
Calibration curve D2 line • Detection limit = 3σ /m • Detection limit observed = (123 + 17) ppm
Calibration curve for D1 line • Detection limit = 3σ/m • Detection limit observed = (116+13) ppm
Calibration curve D2 line • Detection limit = 3σ/m • Detection limit observed = (19+ 5) ppm
Calibration curve for D1 line • Detection limit = 3σ/m • Detection limit observed = (7.8+3) ppm
Detection limit optimization • Two types of background noise; plasma continuum & detector noise. • Optimization Optimum gating time & optimum position of detector. Study of temporal and spatial expansion of plasma in air.
Problems to be fixed and future plans • An actual set up should have the capability to distinguish among several elements. • For that suitable wavelength of laser radiation to be decided. • Suitable energy of laser radiation to be determined. • Plasma parameters (plasma temperature, plasma density) to be determined for different elements. • The LIBS method should be compared with other standard authentic methods. • Salt solution of sodium and magnesium in the form of ice cubes to be analyzed.