Development and application of an LC-MS method to determine possible migration of mercaptobenzothiazole, benzothiazole and related vulcanization residues from rubber used in contact with food and drink

A method was developed for the analysis of food and drink for residues of specific vulcanization accelerators used to cross-link rubber. The method was applied to the analysis of 236 samples of selected retail foodstuffs that may have been in contact with rubber during their manufacture, transport and storage. The method of analysis involved extraction of the food using acidified solvent and analysis by liquid chromatography/atmospheric pressure chemical ionization-mass spectrometry (LC-APcI-MS). The detection limit depended on the sample type and was in the range 0.005-0.043 mg kg(-1) for 2-mercaptobenzothiazole (MBT) and benzothiazole (BT). The average analytical recovery rate was 82% for MBT and 87% for BT. The analytical method was validated using a blind check sample exercise. For MBT and BT at seven different concentrations in the range 0.1-0.2 mg kg(-1), the laboratory found a mean of 91 and 90% of the expected concentrations, respectively. No trace of MBT or BT was found in any of the retail samples. It is also concluded that no sample contained significant 2-mercaptobenzothiazyl disulphide (MBTS) or N- cyclohexyl-2-benzothiazole sulphenamide (CBS). Both MBTS and CBS are important accelerators used to vulcanize rubber and they break down in foodstuffs to form MBT and BT. The absence of MBT and BT in the foodstuffs therefore also provides proof of the absence of MBTS and CBS.