Conversion to isothiocyanates via dithiocarbamates for the determination of aromatic primary amines by headspace-solid phase microextraction and gas chromatography

A novel and highly selective method has been developed for the determination of aromatic primary amines by their conversion to dithiocarbamates by reaction with carbon disulphide, and then to isothiocyanates, which are volatile, by heating in the presence of a heavy metal ion. Zinc(II) was selected owing to its low toxicity and optimum yield of isothiocyanates. The latter were sampled by headspace-solid phase microextraction (HS-SPME) on divinylbenzene-carboxen-polydimethylsiloxane fibre, 50/30 mu m. The HS-SPME procedure was optimized to provide adequate limits of detection in the analysis of aromatic amines in their real samples by gas chromatography with mass spectrometry (GC-MS) or flame ionization detection (GC-FID). The method gave rectilinear calibration graph, correlation coefficient and limit of detection, respectively, over the range 0.08-100 mu gL(-1), 0.9950-0.9990 and 25-240 ng L-1 in gas chromatography-mass spectrometry, and 0.01-10 mg L-1, 0.9910-0.9991 and 0.8-3.0 mu gL(-1) in gas chromatography-flame ionization detection. At two different levels, 10 and 40 mu gL(-1), the range of intraday RSD was 3.7-8.5% (GC-MS) and 3.3-9.2% (GC-FID), respectively. The proposed method is simple and rapid, and has been applied to determine aromatic primary amines in the environmental waters, food samples of ice cream powder and soft drinks concentrate, and food colours. The intra-day RSD in the analysis of real samples by GC-MS was in the range 3.6-6.2%. The food/colour samples were found to contain elevated levels of aniline and 2-toluidine. (C) 2013 Elsevier B.V. All rights reserved.