SERS技术的小白菜中西维因农药残留检测

西维因是一种广谱、高效的氨基甲酸酯杀虫剂。提出一个基于表面增强拉曼光谱进行定量和定性分析小白菜中西维因残留的方法。密度泛函理论B3LYP/6-311G基组被用于计算西维因农药的理论拉曼光谱。硫酸镁、PSA、石墨化炭黑和C18被用来去除叶绿素、矿物质和维生素等物质的影响。采用MSC，SNV和归一化三种方法对原始光谱进行预处理，建立小白菜中西维因残留的偏最小二乘模型。研究表明，小白菜中西维因农药残留检测可以达到0.976 mg·L-1以下。经MSC预处理后所建PLS模型预测性能最好，当主成分数为9时所建模型的性能最好，R_c为0.977，RMSECV为2.09 mg·L-1，R_p为0.986 5，RMSEP为1.71 mg·L-1。五个未知西维因农药浓度小白菜样本用来验证模型的准确度，相对误差为1.98%~7.28%，预测回收率为95.73%~107.28%，T值为0.397, 小于t_{0.05, 4}=2.776，说明模型是准确可靠的。SERS方法是一种有效的方法，可以实现小白菜中西维因农药残留的快速可靠检测。

Study of Rapid Detection of Carbaryl Pesticide Residues in Pakchoi Based on SERS Technology

Carbaryl is a broad-spectrum and efficient carbamate pesticide. In this study, we proposed a surface-enhanced Raman scattering (SERS) approach for quantitative and qualitative analysis of carbaryl residues in pakchoi. Density functional theory(DFT) calculations with Gaussian 03 using B3LYP/6-311G basis sets were executed. The experimental vibrational spectrum and theoretical spectrum of carbaryl were contrasted for its assignments of Raman peaks. Magnesium sulfate, PSA, carbopack and C18 were used to remove the influences of fluorescent substances in pakchoi. The limit of detection can achieve the standard of 0.976 mg·L-1 for carbaryl pesticide residues in pakchoi. Primordial spectra were pretreated by three methods of MSC, SNV and Normalization, and then the spectra were used to construct the pesticide residues models by the method of Partial Least Squares (PLS). Based on the results of PLS, carbaryl residues extracted from pakchoi can be predicted by the MSC model with a lower root mean square error of prediction (RMSEP=1.71 mg·L-1) and higher correlation coefficient in the prediction set (R_p=0.986 5) value. It shows that the model of MSC can accurately predict the carbaryl pesticide residues extracted from pakchoi. Five unknown carbaryl concentration pakchoi samples were prepared for prediction model precision, and the values of relative deviation were calculated to be between 1.98% and 7.28%, and the predicted recovery rates were calculated to be between 95.73% and 107.28%. The T value is 0.397, which is smaller than t_{0.05, 4}=2.776. These demonstrate that there is not evident difference between the measured and predicted values. This study illustrates that SERS method serves as an efficient method for the detection of carbaryl pesticide residues extracted from pakchoi quickly and reliably.