Laser Induced breakdown spectroscopy in Water for elemental analysis .

1. Laser Induced breakdown spectroscopy in Water for elemental analysis. Satyanarayan Ray Pitambar Mohapatra Project Guide: Dr. R.K. Thareja

2. 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).

3. 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).  

4. 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

5. Set up

6. 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

7. 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).

8. Why Na ? • Easily available element to start with. • To determine the concentration of Na in sea ice. • Na concentration in blood and cells.

9. 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

10. Time resolved data for concentration = 38 ppm

11. Time resolved observation for concentration = 102 ppm, gate delay = 300 ns

12. Time resolved data of Sodium line for Concentration = 409 ppm, gate delay = 300 ns

13. Calibration curve D2 line • Detection limit = 3σ /m • Detection limit observed = (123 + 17) ppm

14. Calibration curve for D1 line • Detection limit = 3σ/m • Detection limit observed = (116+13) ppm

15. Calibration curve D2 line • Detection limit = 3σ/m • Detection limit observed = (19+ 5) ppm

16. Calibration curve for D1 line • Detection limit = 3σ/m • Detection limit observed = (7.8+3) ppm

17. 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.

18. 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.