Microwave-assisted laser induced breakdown molecular spectroscopy: quantitative chlorine detection

Quantitative detection of chlorine, through molecular emission from CaCl, using microwave assisted laser induced breakdown spectroscopy (MW-LIBS) has been demonstrated. CaCl emission is utilised in the spectral range of 617.9-621.5 nm. Using time-resolved emission spectra of CaCl at 617.9 nm, following a 1.5 ms microwave pulse, an optimum gate-width and gate-delay have been established. A linear relationship between the intensity of CaCl molecular emission and chlorine concentration on a cement surface has been validated. This yields a limit of detection (LoD) of 47 +/- 7 mu g g(-1) and similar to 170 +/- 59 mu g g(-1) for chlorine, based on 100 shots averaged and a single shot, respectively. The results represent a 10-fold improvement in the chlorine LoD on cement.