Supercritical Fluid Extraction and Gas Chromatography/Ion Trap Mass Spectrometry of Pentachloromtrobenzene Pesticides in Vegetables

Abstract

An analytical approach using supercritical fluid extraction (SFE) followed by gas chromatography/ion trap mass spectrometry (GC/ITMS) was developed for the analysis of the fungicide pentachloronitrobenzene and several analogues in vegetables. The method was tested in the analysis of carrots, potatoes, green beans, celery, and radishes fortified with pentachloronitrobenzene, tetrachloronitrobenzene, pentachloroanisole, pentachlorothioanisole, pentachlorobenzene, hexachlorobenzene, and pentachloroaniline. An incurred carrot sample analyzed by the method was shown to contain hexachlorobenzene at 7 +/- 3 ng/g, which agreed with the concentration (8 +/- 4 ng/g) determined using a traditional solvent-based method. The SFE method consisted of the following steps: (1) homogenizing a 50 g vegetable sample and weighing a 3 g subsample; (2) mixing 2 g sorbent (Hydromatrix) with the subsample to absorb moisture and packing a 10 mL extraction vessel; (3) extracting with 40 mL CO2 at 200 atm, 40 degrees C, and a flow rate of 3 mL/min; and (4) collecting the extract on a 1 g alumina basic trap at 25 degrees C and flushing with 8 mL isooctane. Collection of the extract on alumina efficiently removed chlorophyll and other matrix interferences. GC/ITMS in the electron-impact mode confirmed and quantitated the analytes at concentrations as low as 1 ng/g.