Development And Application Of Pesticide Multi-residue Pretreatment Method Based On Multi-walled Carbon Nanotubes

Pesticide residue analysis is an analysis technique of the trace components in complex mixture, which requires high sensitivity and specificity. The concentration of the analytes in the samples is very low and the composition of the samples is really complex, so the interference of matrix background is the key problem. Recently, based on reversed dispersive solid-phase (r-DSPE), QuEChERS method has been widely used, which is simple, rapid, safe, and cheap. It simplies the extraction steps, reduces solvent consumption, and speeds up the sample preparation process. R-DSPE is easy and quick, but when it comes to some complex matrices, the cleanup performance is not good enough. In this study, based on multi-walled carbon nanotubes (MWCNTs), a modified reversed dispersive solid-phase extraction method in QuEChERS method is developed and rapid muti-plug filtration cleanup (m-PFC) method is designed, at the same time the interaction between MWCNTs and interference substances is explored.A pesticide residue analysis method based on r-DSPE using MWCNTs is developed in this study, which is validated on many kinds of matrices and pesticides. In this study, the type and amount of MWCNTs are optimised, and recoveries, limits of detection, limits of quantification, matrix effect are also validated. Moreover, the proposed method is compared with the traditionally QuEChERS method. For most cases, the average recoveries were in the range of70%-110%with relative standard deviations lower than15%. The proposed method is applied to real samples in markets.Rapid multiplug filtration cleanup with MWCNTs for pesticide residue analysis is designed in this study. The proposed method validated on many kinds of matrices and pesticides. During the experiment, sample preparation method and instrument condition are optimised. Recoveries, limits of detection, limits of quantification, matrix effect are validated. The proposed method is also used to detect the real samples from markets. For most cases, the average recoveries were in the range of70%-110%with relative standard deviations lower than15%The interaction between MWCNTs and interference substances is studied using TEM and the theory of matrix interference removal is expored. During the experiment, TEM images of MWCNTs before and after r-DSPE process are compared, and two kinds of interactions between MWCNTs and interference substances are observed.In this study, it is shown that MWCNTs could be used as a alternative r-DSPE materials or mixed with other kinds of sorbent to enhance the cleanup performance. M-PFC method could be applied for pesticide residue analysis since it is rapider and easier than the other traditionally method. The theory of matrix interference removal by MWCNTs was expored.