Micro determination of 2-mercaptobenzothiazole in water and sediment by gas chromatography with a flame photometric detector

Micro determination of 2-mercaptobenzothiazole (2-MBT) in water and sediment samples was studied. After 11 of a water sample was adjusted to pH 34 with 1 M hydrochloric acid, 2-MBT was extracted with 50 ml each of dichloromethane twice. In case of sediment samples, 200 ml of distilled water was added to a sample, and the pH of the solution was adjusted to 1011 with 1 M sodium hydroxide. The mixture was filtered after vigorous shaking for 10 min. The filtrate was washed with 50 ml of dichloromethane to remove neutral and basic organic substances. 2-MBT was extracted twice with 50 ml each of dichloromethane after the pH of the aqueous layer being adjusted to 34 with 1 M hydrochloric acid. The extract was dried through an anhydrous sodium sulfate column and concentrated to 1 ml with a KD evaporator under atmospheric pressure. The concentrated sample was further reduced to 0.1 ml with nitrogen gas stream. 2-MBT was methylated with dimethyl-formamide diacetal for 15 min at 60°C to 2-methyl-mercaptobenzothiazole (2-MMBT) and 2-MMBT was determined by gas chromatography with a flame photometric detector. Recoveries of 2-MBT for a water sample were 75% and 40% at 100μg and 1 μg added to samples, respectively. For determination of 2-MMBT, dibenzothiophene was used as an internal standard. Detection limits of 2-MBT in a water sample (11) and sediment sample (20 g) were 0.04 ppb, and 2 ppb, respectively. This method was applied to some environmental samples. 2-MBT was detected in the range of (4.644)ppb in river sediment samples, but not detected for the water samples and marine sediment samples examined.