Gas chromatography-mass spectrometry using microvial insert thermal desorption for the determination of BTEX in edible oils

Microvial insert thermal desorption is evaluated as a sample introduction system for gas chromatography-mass spectrometry (GC-MS) determination of benzene, toluene, ethylbenzene and xylene isomers (BTEX) in vegetable oil samples. Under the optimized conditions, the BTEX contained in a 50 mu L oil sample placed in the microvial insert were thermally vaporized at 140 degrees C for 5 min while helium at a flow of 120 mL min(-1) and pressure of 4.3 psi propelled the analytes to the programmable temperature vaporizator (PTV), where they were focused at 15 degrees C. The compounds were finally injected into the GC column by rapidly heating the PTV at 270 degrees C. The proposed method provided good linearity between 10 and 200 mu g L-1. High sensitivity, with detection limits in the 0.7-1.2 mu g L-1 range, depending on the compound, was achieved with a low sample volume and minimum sample handling. Fourteen edible vegetable oil samples were analyzed and the analytes were found in a wide concentration range.