SERS结合快速前处理检测绿茶中毒死蜱农药残留

茶叶是中国的主要经济作物之一,而在茶叶种植过程中存在农药不合理使用及滥用等行为,导致茶叶中存在严重农药残留问题。茶叶中农药残留检测主要采用经典化学实验室方法,存在前处理复杂、耗时长、成本高等缺陷,急需研究茶叶中农药残留的快速检测方法,以监管茶叶市场的质量安全。本论文采用纳米竹炭(NBC)为净化剂快速去除绿茶的色素等基质影响,使用表面增强拉曼光谱(SERS)方法分析绿茶中毒死蜱农药残留,建立绿茶中毒死蜱农药残留的SERS快速检测方法。采用不同NBC用量(0,15,20,25和30 mg)去除茶叶基质,比较不同NBC用量去除基质的净化效果和SERS谱图,得出最优NBC用量,并对前处理方法进行回收率实验,验证前处理方法的可靠性。结果表明,使用20 mg NBC能较好地净化绿茶中的色素等基质影响,前处理方法回收率实验表明,该净化剂用于绿茶中毒死蜱农药残留基质净化是可行的。采用密度泛函理论模拟毒死蜱分子理论拉曼光谱,对比毒死蜱分子理论拉曼光谱和实验拉曼光谱,对其官能团进行谱峰归属,得到定性定量分析绿茶中毒死蜱农药残留的5个特征峰:526,560,674,760和1096 cm-1。在0.28~11.11 mg·kg-1浓度范围内,以1096 cm-1的峰强度建立绿茶中毒死蜱农药残留线性分析方程y=0.0175x+0.9092,决定系数为R 2=0.9863,表明毒死蜱农药浓度与其特征峰强度之间具有良好的线性关系,方法的平均回收率在96.71%~105.24%之间,相对标准偏差(RSD)为2.36%~3.65%。该方法检测绿茶中毒死蜱农药的最低检出浓度约为0.56 mg·kg-1,单个样本检测时间在15 min内完成。研究表明,表面增强拉曼光谱技术结合净化剂前处理方法能快速检测绿茶中的农药残留。

Detection of Chlorpyrifos Residues in Green Tea Using SERS and Rapid Pretreatment Method

Tea is one of the main economic-crops in China.During tea planting,the unreasonable use and abuse of pesticides lead to serious pesticide residues in tea.At present,the classical chemical laboratory methods are adopted to detect the pesticide residues in tea,but there are some shortcomings such as complex pretreatment,time-consumption and high cost in the laboratory methods.Therefore,it is urgent to study the rapid detection method of pesticide residues in tea to supervise the quality and safety of tea market.In this study,Nano Bamboo Charcoal(NBC)purifier was used to reduce the matrix-induced enhancement of tea substrate.Surface-enhanced Raman spectroscopy(SERS)was employed to detect Chlorpyrifos residues in green tea,and a rapid detection method for analyzing Chlorpyrifos residues in green tea was developed.Different doses of NBC(0,15,20,25,30 mg)were used to remove the matrix effects.The optimal dosage of NBC was obtained by comparing the purification effect and SERS of different NBC dosage.The recovery experiment was carried to verify the reliability of the optimized pretreatment method.The results showed that NBC had obvious purification effect and the green tea substrates such as pigment and so on matrix-induced enhancement were reducing when the dosage of NBC was 20 mg.It was proved that this optimized pretreatment method was suitable for decreasing the matrix-induced enhancement of tea substrate by recovery tests.Density functional theory was used to simulate the theory Raman spectrum of chlorpyrifos.The theoretical and experimental Raman spectrums of chlorpyrifos were compared and spectral peaks of their functional groups were assigned.Five characteristic peaks of Chlorpyrifos in green tea such as 526,560,674,760 and 1096 cm-1 were found.Within the scope of the concentration of 0.28~11.11 mg·kg-1,a line relation was developed between the peak intensity of 1096 cm-1 and the concentration of Chlorpyrifos of tea extract,y=0.0175x+0.9092 and R 2 was 0.9862,indicating a good linear relationship.The average recovery rates of the method were 96.71%~105.24%,and the relative standard deviations(RSD)were between 2.36%~3.65%.The minimum detection concentration of Chlorpyrifos residues detected by this method was about 0.56 mg·kg-1 and the detection time of a single sample was performed within 15 minutes.The result demonstrated that SERS combined with rapid pretreatment method was feasible for rapidly detecting pesticide residue in tea.