Isothiazolinone biocides are broad-spectrum preservatives that are widely used in cosmetics, household, and industrial products. An increase in the number of cases of allergic contact dermatitis to isothiazolinone preservatives, namely, methylisothiazolinone and methylchloroisothiazolinone, have been recently noticed. The Food and Drug Administration relies on analytical methods to quantify levels of use of cosmetic ingredients and support enforcement action against products that are not in compliance with the law. In this study, an efficient ultra high performance liquid chromatography with tandem mass spectrometry method was developed and validated for the determination of methylisothiazolinone and methylchloroisothiazolinone in selected cosmetic products. The lower limit of quantitation was determined to be 0.1 μg/g for both preservatives. A survey of 24 cosmetic products was conducted and found concentrations of methylisothiazolinone and methylchloroisothiazolinone ranging from not quantified, or below the lower limit of quantitation, to 89.64 μg/g and not quantified to 10.31 μg/g, respectively.

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A method using gas chromatography with mass selective detection for the determination of ethyl carbamate (EC; also known as urethane) in alcoholic beverages and soy sauce was collaboratively studied by 17 laboratories including authors’ laboratories. The method uses prepacked columns for extraction of liquids with methylene chloride, and n-propyl carbamate as the internal standard. A practice sample and 6 samples of distilled spirits, fortified wines, table wines, and soy sauces were analyzed by each collaborator. Each matrix included blind duplicates of incurred and fortified EC at 3 levels. Distilled spirits contained 50–330 ng EC/g (ppb), fortified wine 40–160 ppb, table wine 10–50 ppb, and soy sauce 15–70 ppb. The ranges of the repeatability relative standard deviations, excluding outliers, were 4.03–6.63% for distilled spirits, 4.01–5.05% for fortified wine, 3.94–6.73% for table wine, and 4.70–8.49% for soy sauce. The ranges of the reproducibility relative standard deviations, excluding outliers, were 8.53–9.49% for distilled spirits, 6.84–12.02% for fortified wine, 8.86–18.47% for table wine, and 13.87–27.37% for soy sauce. Recoveries of added EC ranged from 87 to 93%. Recoveries relative to reference values, labeled as the internal standard, obtained by using gas chromatography/ tandem mass spectrometry with a triple quadrupole mass spectrometer ranged from 89 to 100%.