Analysis of kresoxim-methyl and its thermolabile metabolites in Korean plum: An application of pepper leaf matrix as a protectant for GC amenable metabolites

Authors


Correspondence: Professor Jae-Han Shim, Natural Products Chemistry Laboratory, Biotechnology Research Institute, Chonnam National University, Gwangju 500-757, Republic of Korea

E-mail: jhshim@chonnam.ac.kr

Fax: +82-62-530-0219

Additional correspondence: Prof. A. M. Abd El-Aty, e-mail: abdelaty44@hotmail.com

Abstract

A new method was developed for kresoxim-methyl (parent compound) and its two thermolabile metabolites, BF 490-2 and BF 490-9, in Korean plum, introducing pepper leaf matrix as a natural analyte protectant for GC-amenable metabolites using a GC-electron capture detector. Samples were extracted with a simple and rapid method using a mixture of ethyl acetate–n-hexane (1:1) and salts, and purified via SPE. Due to the elution gap between parent compound and metabolites in the SPE cartridge and matrix interference, kresoxim-methyl was isolated separately from its metabolites. An optimized amount of pepper leaf matrix (0.25 g/mL) was added to the metabolites prior to each injection. Calibration curves were linear over the concentration ranges with coefficient of determination (r2) ≥ 0.999. The method was validated in triplicate at two fortification levels, giving recoveries ranging between 74.3 and 101.4%, and RSDs less than 5%. The LOD and LOQ were 0.015 and 0.05 mg/kg, respectively. The method was successfully applied to real samples where kresoxim-methyl residues were detected in field-incurred plum samples. Residues were confirmed using GC-MS.

Ancillary