Laser induced breakdown spectroscopy characterization of Ca in a soil depth profile

Laser induced breakdown spectroscopy (LIBS) was used for the analysis of Ca in a soil depth profile of Patagonia (Argentina), using a CO2 TEA Laser and solid pellets of the soil in a BaCl2 matrix. The experimental set-up allowed for the simultaneous observation of the emission lines in the range 390–420 nm, corresponding to Ca(II) and Ba(II), so that the intensity ratio I(Ca)/I(Ba) could be measured to obtain a calibration curve, rather than I(Ca) alone. The results of the ablation could be interpreted with an evaporation model and non-stoichiometric conditions. The experimental variables such as laser energy, number of pulses averaged, and Ca concentration in the pellet were evaluated in order to find the best conditions for the analysis. The samples were obtained at variable depths (from 0 to 18 m) and analyzed to measure the total Ca and the acid soluble Ca. These results were compared with those obtained with the standard techniques.