Quantification of a mercapturate metabolite of the biocides methylisothiazolinone and chloromethylisothiazolinone (“M-12”) in human urine using online-SPE-LC/MS/MS

Analytical Methods, vol. 13, pp. 1847–1856

Abstract

Methylisothiazolinone and the reaction mixture of chloromethylisothiazolinone/methylisothiazolinone (MCI/MI, 3 : 1) are broadly used biocides that are contained in many products of everyday life (e.g. cosmetics, wet wipes, etc.). As MI and MCI are able to sensitize (and penetrate) the skin, their application in cosmetic products is of concern. In previous work, we have revealed a background exposure of the general population to MI and/or MCI/MI (3 : 1) by the determination of urinary N-methylmalonamic acid (NMMA) as the main human metabolite. To corroborate these findings, we have now developed a two-dimensional LC/MS/MS method for the quantification of a mercapturic acid metabolite of MI and MCI ((acetylamino){[3-(methylamino)-1-(methylthio)-3-oxopropyl]thio}acetic acid or shortly "M-12") in human urine. This analyte is enriched online using a Strata-X-column and stripped from the urinary matrix. Then, the analyte is back flushed to the analytical column (Phenomenex C18(2), 150 × 4.6 mm) and finally quantified by tandem mass spectrometry with the use of isotopically labelled M-12 as the internal standard. The LOQ for M-12 was 0.2 ng mL-1 urine and sufficient to quantify urinary background levels. Precision within and between series for M-12 in urine at concentrations varying from 0.2 to 5 ng mL-1 ranged from 2.1 to 23.9% and accuracy ranged from 86.3 to 101.8%. Mean accuracy for M-12 in individual urine samples was 94.3% (range: 89.7-102.9%). We applied this method to previously collected 24 h urine samples of 60 persons with no specific exposure to MI and/or MCI/MI (3 : 1). The metabolite M-12 could be quantified in each urine sample. The median and 95th percentile levels for urinary M-12 were determined to be 0.62 and 2.26 ng mL-1, respectively. In these urine samples, the concentrations of the previously determined metabolite NMMA and M-12 correlated well. In the future, we will apply this method to urine samples of a previously conducted human exposure study to explore the additional value of M-12 as a biomarker of exposure to MI and MCI.

Authors 5

1. Thomas Schettgen corresponding Aachen Medical Faculty Institute for Occupational, Social and Environmental Medicine

   RWTH Aachen University

   Affiliation as printed

   D-52074 Aachen

   Germany

   Institute for Occupational, Social and Environmental Medicine

   Medical Faculty

   RWTH Aachen University

   Institute for Occupational, Social and Environmental Medicine, Medical Faculty, RWTH Aachen University, Pauwelsstrasse 30, D-52074 Aachen, Germany

2. Jens Bertram Aachen Medical Faculty Institute for Occupational, Social and Environmental Medicine

   RWTH Aachen University

   Affiliation as printed

   D-52074 Aachen

   Germany

   Institute for Occupational, Social and Environmental Medicine

   Medical Faculty

   RWTH Aachen University

   Institute for Occupational, Social and Environmental Medicine, Medical Faculty, RWTH Aachen University, Pauwelsstrasse 30, D-52074 Aachen, Germany

3. Till Weber

   German Environment Agency

   Affiliation as printed

   Berlin

   German Environment Agency (UBA)

   Germany

   German Environment Agency (UBA), Corrensplatz 1, Berlin, Germany

4. Thomas Kraus Aachen Medical Faculty Institute for Occupational, Social and Environmental Medicine

   RWTH Aachen University

   Affiliation as printed

   D-52074 Aachen

   Germany

   Institute for Occupational, Social and Environmental Medicine

   Medical Faculty

   RWTH Aachen University

   Institute for Occupational, Social and Environmental Medicine, Medical Faculty, RWTH Aachen University, Pauwelsstrasse 30, D-52074 Aachen, Germany

5. Marike Kolossa‐Gehring

   German Environment Agency

   Affiliation as printed

   Berlin

   German Environment Agency (UBA)

   Germany

   German Environment Agency (UBA), Corrensplatz 1, Berlin, Germany