Comparison of ATR/transmittance FTIR combined with Beer's law and PLS to determine fipronil in matrine formulation

The rapid analysis of fipronil in pesticide preparations is demanded because use of this pesticide is restricted and even prohibited in many countries. The objective of present work is to compare four methodologies for quantitative analysis of fipronil in matrine by ATR/transmittance FTIR combined with Beer's law and partial least squares (PLS) analysis. To remove aqueous solvent, 0.2 ml each sample was dried under an infrared lamp and subsequently re-dissolved in 1 ml acetonitrile. Good calibration curves of Beer's law with correlation coefficients (R2) of 0.9982 (H1322) for ATR spectra and 0.9843 (H1324), 0.9821 (H1634) for transmittance second derivative spectra were achieved; and in the PLS calibration, the the root mean square error of prediction (RMSEP) of fipronil were 0.00197, 0.00580 and R2 of validation set were 0.9970, 0.9758 for ATR and transmittance, respectively. These methods are all acceptable and demonstrate the possibility of quick detection of fipronil in matrine by FTIR spectroscopy.