Quantitative analysis of nitrogen in ammonium phosphate fertilizers using laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy (LIBS) coupled with the linear multivariate calibration method was applied to analyze nitrogen (N) quantitatively in ammonium phosphate fertilizers. The intensity of lines N (NI:742.4, 744.2, 746.8, 856.7, 859.4, 862.9, 870.3, 871.2, 871.8 nm) and O (OI:777.2, 844.6, 882.0 nm) were used as independent variables for the models. To verify the accuracy of the models, the unary, binary, ternary, and quaternary variables were chosen to establish the linear regression equations. The results of the linear models showed that the quaternary model was better than the other three models. The correlation coefficient of the quaternary linear model was 0.981 and the maximum relative error of the validation samples was 4.32%.