An alternative analysis for chlorpyrifos residues in tea by using surface-enhanced Raman spectroscopy
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Oblique angle deposition (OAD) SERS substrate deposited at a vapor incident angle of 86° demonstrates feasibility of rapid screening chlorpyrifos residues in tea. The standard SERS spectra of chlorpyrifos, an organophosphate pesticide, were established for further analysis. The instrumental detection limit of chlorpyrifos achieves 0.05 ppm. The calibration curves of chlorpyrifos based on Raman areas at bands 419, 691, 1343, and 1575 cm-1 have better correlation coefficients (0.9609-0.9918) than that based on Raman intensity (0.9436-0.9731) in the concentration range of 0.2-100 ppm. SERS spectra for chlorpyrifos left on tea samples were demonstrated based on band 1032, 1280, 1342, and1575 cm-1. This study clear differentiate and identify SERS spectra difference between chlorpyrifos and parathion where gas chromatography method has difficulty to separate. Our results suggest that the SERS combined with principle component analysis (PCA) can be used to identify pesticide residues in food systems via identifying the minute different fingerprints.