The identification and concentration of heavy metals, which may be so harmful for the body, is determined by the method of calibration-free laser-induced breakdown spectroscopy using a special strategy. First, the plasma temperature is obtained using the Boltzmann plot. Then, a line with an inappreciable self-absorption is considered for each element as the reference. The modified intensities of other lines of the element are calculated through their self-absorbed intensities in terms of the reference intensity. The plasma temperature is again computed by line pair ratio method. This procedure is carried out by an iterative algorithm until the self-absorption coefficient of selected lines converges on one. In the last step, the corrected temperature is evaluated by the Boltzmann plot drawn using true (non self-absorbed) line intensities of each element. The concentration of the elements is finally determined by the corrected temperature and intensities. The results indicate that the accuracy of this method in determining the concentrations is significantly better than the normal way.

Keywords: LIBS, plasma temperatures, quantitative analysis, self-absorption, heavy metals.

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