Headspace solid-phase microextraction and on-fibre derivatization of primary aromatic amines for their determination by pyrolysis to aryl isothiocyanates and gas chromatography-mass spectrometry

Abstract

A sensitive and solvent-free procedure for the determination of aromatic amines in environmental and food samples was studied using solid-phase microextraction (SPME) for on-fibre derivatization and gas chromatography-mass spectrometry (GC-MS). The analytical procedure involved headspace impregnation of allyl isothiocyanate on the SPME fibre and then extraction/derivatization of aromatic amines by placing impregnated fibre in the headspace of the sample. The allyl thiourea derivatives were pyrolyzed in the injection port of the GC and the aryl isothiocyanates thus formed were chromatographed. SPME parameters such as selection of coating material, extraction/derivatization time and temperature were optimized. The optimum extraction was obtained using a divinylbenzene/carboxen/polydimethylsiloxane fibre placed for 20 min in the headspace of the sample heated to 70 °C. This method increased the extractability and detectability of aromatic amines from complex environmental and food samples. The calibration curves for derivatized amines were linear in the range 0.05–100 μg L⁻¹ with correlation coefficients in the range 0.9946–0.9994 and limits of detection in the range 6–180 ng L⁻¹. Many real samples including food colours, ice cream powder, soft drink concentrate, and industrial area sand have been analyzed and were found to contain elevated levels of aromatic amines.