LC-MS/MS Method Minimizing Matrix Effect for the Analysis of Bifenthrin and Butachlor in Chinese Chives and Its Application for Residual Study

Abstract

The matrix effect refers to the change in the analytical signal caused by the matrix in which the sample is contained, as well as the impurities that are co-eluted with the target analyte. In crop sample analysis using LC-MS/MS, the matrix effect can affect the quantification results. Chinese chives are likely to exhibit a strong matrix effect when co-extracted with bifenthrin and butachlor due to the presence of phytochemicals and chlorophyll. A novel analytical method was developed to reduce the matrix effects of bifenthrin and butachlor to a negligible level in Chinese chives. The established method had a limit of quantitation of 0.005 mg/kg and correlation coefficients greater than 0.999 within the range of 0.005-0.5 mg/kg. Matrix effects were found to be negligible, with values ranging from -18.8% to 7.2% in four different sources of chives and two leafy vegetables. Compared to conventional analytical methods for the LOQ and matrix effect, the established method demonstrated improved performances. The analytical method was further applied in a residual study in chive fields. The active ingredient of butachlor 5 granule (GR) was not detected after soil admixture application, while that of bifenthrin 1 emulsifiable concentrate (EC) showed a range from 1.002 to 0.087 mg/kg after foliar spraying. The dissipation rate constant (k) of bifenthrin was determined to be 0.115, thus its half-life was calculated to be 6.0 days. From the results, PHI and safety use standards of both pesticides were suggested. The developed analytical method can be applied to accurately determine bifenthrin and butachlor residues in Chinese chives and provides a foundation for further research on the fate and behavior of these pesticides in the environment.

Keywords: Chinese chives; LC–MS/MS; QuEChERS; bifenthrin; butachlor; matrix effect.

Figure 1

A design layout of the experimental fields in (a) Jeonju-si for bifenthrin 1 EC; (b) Jincheon-gun for butachlor 5 GR.

Figure 2

Chromatograms for bifenthrin and butachlor using the established MRM conditions; (a) blank samples without bifenthrin, (b) bifenthrin matrix-matched standard at LOQ (0.005 mg/kg), (c) bifenthrin recovery sample at 0.01 mg/kg, (d) bifenthrin residue sample (T4; 30-21), (e) blank samples without butachlor, (f) butachlor matrix-matched standard at LOQ (0.005 mg/kg), (g) butachlor recovery sample at 0.01 mg/kg, (h) butachlor real sample (T5).

Figure 3

Colorimetric estimation of extract solutions for various purification methods. (a) Extraction with MeCN; (b) Extraction with MeCN/EA (1:1, v/v). The methods corresponding to capital letters A to D in this figure are as follows: A, PSA d-SPE; B, PSA + GCB d-SPE; C, HLB; D, PSA + GCB d-SPE and HLB combination.

Figure 4

Dissipation patterns of bifenthrin residue in chives.