Rapid and sensitive LC–MS–MS determination of 2-mercaptobenzothiazole, a rubber additive, in human urine
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2-Mercaptobenzothiazole (MBT) is one of the most important vulcanization accelerators in the industrial production of rubber, especially car tires. Given its wide use in household articles and industrial rubber products it has a high potential to migrate into the environment. Humans can be exposed by dermal, oral, or inhalative routes. Incorporated MBT is excreted in urine, mainly as conjugates to glucuronide, sulfate, and mercapturic acid. On the basis of these facts MBT has been selected as a substance of high interest in the large scale 10-year German project on human biomonitoring (HBM); a cooperation between the German Federal Ministry for the Environment (BMUB) and the German Chemical Industry Association (VCI) with the objective of developing new analytical methods for relevant chemicals. The presented method was developed to determine MBT in human urine to reliably investigate the internal human MBT dose. Total MBT is measured after enzymatic hydrolysis followed by application of high-pressure liquid chromatography tandem mass spectrometry (HPLC–MS–MS) in positive-electrospray-ionization mode (ESI+) using isotope-dilution quantification. High sample throughput could be obtained by use of the column-switching technique. Optimization yielded an analytical method with a low and reproducible limit of detection (LOD) of 0.4 μg L−1 and a limit of quantification (LOQ) of 1 μg L−1, and low relative standard deviations in the range 1.6–5.8 %. A small biomonitoring study covering unexposed humans and occupationally exposed workers was performed to establish the feasibility and reliability of the method. MBT was found in only one urine sample from the unexposed humans, at a value of 10.8 μg MBT per liter, whereas it was found in all samples from the tested workers at values of up to 6210 μg MBT per liter.
Keywords2-Mercaptobenzothiazole MBT Urine Conjugates Excretion LC–MS–MS Biomonitoring
The development of this method of analyzing MBT found in the human body (including the synthesis of the internal standard) was funded by the German chemicals industry. The method was developed during an ongoing 10-year project on human biomonitoring. The project is a cooperation agreed in 2010 between the Federal Ministry for the Environment, Nature Conservation, Building and Nuclear Safety (BMUB) and the Verband der chemischen Industrie e.V. (German Chemical Industry Association – VCI); it is administered by the Federal Environment Agency (UBA). Experts from government authorities, industry, and science accompany the project in selecting substances and developing methods.
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