Phosphorus quantification in fertilizers using laser induced breakdown spectroscopy (LIBS): a methodology of analysis to correct physical matrix effects

The aim of this study was to develop a quantitative method to determine phosphorus in fertilizers of different matrix compositions using the laser induced breakdown spectroscopy (LIBS) technique. The LIBS spectra were acquired on 26 samples of organic and inorganic fertilizers by using a low cost, portable, gated CCD system in the atmospheric environment. Inductively coupled plasma optical emission spectroscopy (ICP-OES) was used as the reference technique. A method was developed to remove the outlier spectra and perform the baseline correction and peak normalization. By applying the proposed corrections, the linear correlation between LIBS and ICP increased from R 1/4 0.76 to R 1/4 0.95. An average error of 15% found in cross-validation of LIBS quantification appeared feasible for P quantification in fertilizers. Two reference samples with different matrix compositions were also analyzed, and the absolute error in the quantification was below 5%. Further, no significant fluctuation was found in P quantification when LIBS was performed over 150 days.