Detection of Pesticide (Chlorpyrifos) Residues on Fruit Peels Through Spectra of Volatiles by FTIR

The fast measurement of pesticide residues on fruits peels is crucial, for it is harmful for both human health and environment. In this study, we used apples and chlorpyrifos as the research materials and analyzed the volatiles from apples via its infrared spectra. As the low concentration of the volatiles, multi-reflecting mirrors were used to enhance the sensitivity of the spectroscopy system. From the experiment, two obvious spectral characteristics from chlorpyrifos, 990-2830 and 1259-1227 cm(-1), has been observed. By analyzing the infrared spectra of the volatiles released from chlorpyrifos with different dilution ratios on the apple peels, we found the spectral intensities increased with the chlorpyrifos concentrations. The results were further analyzed using chemometrics, it is demonstrated that there are obvious spectral differences among the apples sprayed with 1:20, 1:100, and 1:1000 chlorpyrifos and clean apples. The above four groups of the samples can be classified using principal component analysis (PCA). This study demonstrated that gas-phase long-path infrared spectroscopy is an effective method to detect the pesticide residues on fruits peels, with the advantages of no sample treatment and fast. To the best of our knowledge, this is the first study to detect pesticide residues on fresh and untreated apples using infrared spectroscopy via its volatiles.