Abstract: A simple,rapid and environment-friendly method was developed for determination of trace chlorpyrifos in pesticide solution formulations by near infrared (NIR). Two samples with different liquid backgrounds, namely simple background and complex background were designed to measure trace chlorpyrifos by the method. By pre-processing methods of the second derivative +17 point smooth and the first derivative +21 point smooth and partial least square regression (PLS), quantitative analyses of samples were carried out in effective wavelength ranges. The results proved that NIR is appropriate to analyze the mixing solutions containing 3 mg/kg to 10 mg/kg chlorpyrifos.

Key words: near infrared, trace level, pesticide, chlorpyrifos