Gas chromatography-mass spectrometric determination of total isothiocyanates in Chinese medicinal herbs

A gas chromatography-mass spectrometric (GC-MS) method for the determination of total isothiocyanates (ITCs) has been developed based on the quantification of the cyclocondensation product, 1,3-benzodithiole-2-thione, between ITCs and 1,2-benzenedithiol. It was the first analytical application to be applied to the analysis of Chinese medicinal herbs including Laifuzi, Baijiezi, Tinglizi and Hancai, and seeds of commonly consumed vegetables. A considerable variation in ITC contents was observed. The highest concentrations of total ITCs were found to be 20.3 (mu)mol/g in Laifuzi and 12.6 (mu)mol/g in seeds of Chinese kale. The method demonstrates the usefulness of the cyclocondensation of ITCs with 1,2-benzenedithiol reagent for quantifying total ITC contents in Chinese medicinal herbs regardless of the types of ITC. The linear dynamic range covered from 0.12 to 200 (mu)M ITC. The limit of detection (3Sb) was 35 nM and the corresponding absolute detection limit was 35 fmol. The proposed GC-MS technique provides a reliable, unambiguous, reproducible, and efficient method for determining total ITCs of various samples.