title: Quantification of N-methylmalonamic acid in urine as metabolite of the biocides methylisothiazolinone and chloromethylisothiazolinone using gas chromatography-tandem mass spectrometry.
abstract: Methylisothiazolinone and the mixture of chloromethylisothiazolinone/methylisothiazolinone (MCI/MI, 3:1) are widespread biocides used in cosmetic and household products. Due to their skin permeability, they might be taken up by the general population via use of products containing these biocides. As both compounds are known skin sensitizers, the use of these products is under discussion by regulatory agencies. In order to evaluate the possible uptake of MI and/or MCI/MI by human biomonitoring, we have developed and validated a highly sensitive and specific GC/MS/MS-method for the quantification of N-methylmalonamic acid (NMMA), a known metabolite of MI and MCI in urine of rats. After freeze-drying of urine, the analyte is derivatised with pentafluorobenzyl bromide in anhydrous solution and the PFB-derivative is extracted into n-hexane. After concentration, the derivative is finally quantified by GC/MS/MS in EI-mode using13C3-NMMA as internal standard. The limit of quantification for NMMA was 0.5ngmL-1urine. Precision within and between-series was determined to range between 3.7-10.9% using native and spiked quality control samples. Accuracy ranged between 89 and 114%. In a pilot study we applied this method to spot urine samples of 63 persons not knowingly exposed to MI and/or MCI/MI. NMMA was quantifiable in every urine sample analysed, with no significant difference in urinary levels between male and female participants. The median (95th percentile) levels for urinary NMMA were 3.6 (7.4) ngmg-1creatinine and 2.9 (9.1) ngmg-1creatinine for males (n=32) and females (n=31), respectively. In a volunteer experiment, a relation of exposure to MI and/or MCI/MI and subsequent NMMA-excretion was shown. Our method is the first to report human urinary background levels of NMMA. However, the possibility of formation and urinary excretion of NMMA within physiological processes cannot be ruled out.
authors.affiliation: Institute for Occupational and Social Medicine, Medical Faculty, RWTH Aachen University, Pauwelsstrasse 30, D-52074, Aachen, Germany. Electronic address: tschettgen@ukaachen.de.
authors.forename: T
authors.initials: T
authors.lastname: Schettgen
authors.affiliation: Institute for Occupational and Social Medicine, Medical Faculty, RWTH Aachen University, Pauwelsstrasse 30, D-52074, Aachen, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Bertram
authors.affiliation: Institute for Occupational and Social Medicine, Medical Faculty, RWTH Aachen University, Pauwelsstrasse 30, D-52074, Aachen, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Kraus
mesh_terms: D000328:Adult; D000818:Animals; D004202:Disinfectants / Q000652:urine*; D005260:Female; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D006801:Humans; D016014:Linear Models; D008297:Male; D008314:Malonates / Q000652:urine*; D008875:Middle Aged; D051381:Rats; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D053719:Tandem Mass Spectrometry / Q000379:methods*; D013844:Thiazoles / Q000652:urine*; D055815:Young Adult
chemical_list: D004202:Disinfectants; D008314:Malonates; D013844:Thiazoles; C011506:2-methyl-4-isothiazolin-3-one; C061666:N-methylmalonamic acid
keywords: Biocides; Human biomonitoring; Metabolism; Pentafluorobenzyl bromide; Urine