Analysis of low-volatility pesticides in cabbage by high temperature comprehensive two-dimensional gas chromatography

Abstract

High-temperature comprehensive two-dimensional gas chromatography (HTGC × GC) using a longitudinally modulated cryogenic system (LMCS) was developed for the analysis of low-volatility pesticides in cabbage. The method applied DB-17HT and DB-5HT as the first and second dimensional (¹D and ²D) columns, respectively. Twelve pesticides, namely 6 organochlorines (4,4′-DDT, β-endosulfan, endosulfan sulfate, endrin, heptachlor, and dicofol), 4 carbamates (metolcarb, isoprocarb, methiocarb, and carbofuran), 1 organophosphate (chlorpyrifos), and 1 pyrethroid (permethrin), were spiked into cabbage samples and prepared using QuEChERS. The applied oven temperature was up to 340 °C, enabling the elution of all the target pesticides and the matrix. The effects of initial oven temperature program, temperature ramp rate, LMCS trap temperature, and modulation period (P_M) on the separation results were investigated, leading to the suitable conditions of 80 °C, 15 °C min⁻¹, 10 °C, and 12 s, respectively. The method detection limits, signal-to-noise ratio, and recoveries of the compounds were within the ranges of 0.01–0.09 mg kg⁻¹, 4.26–32.7, and 78–104%, respectively. Good linearity ranges within the concentration range of 0.1–1 ppm with R² > 0.9134 were also obtained with the intra and interday precisions of the peak areas of 0.4–9.8% and 1.0–10.2%, respectively.