Novel exposure biomarkers of N,N-diethyl-m-toluamide (DEET): Data from the 2007-2010 National Health and Nutrition Examination Survey.

BACKGROUND: N,N-diethyl-m-toluamide (DEET) is a widely used insect repellent in the United States. OBJECTIVES: To assess exposure to DEET in a representative sample of persons 6years and older in the U.S. general population from the 2007-2010 National Health and Nutrition Examination Survey. METHODS: We analyzed 5348 urine samples by using online solid-phase extraction coupled to isotope dilution-high-performance liquid chromatography-tandem mass spectrometry. We used regression models to examine associations of various demographic parameters with urinary concentrations of DEET biomarkers. RESULTS: We detected DEET in ~3% of samples and at concentration ranges (>0.08µg/L-45.1µg/L) much lower than those of 3-(diethylcarbamoyl)benzoic acid (DCBA) (>0.48µg/L-30,400µg/L) and N,N-diethyl-3-hydroxymethylbenzamide (DHMB) (>0.09µg/L-332µg/L). DCBA was the most frequently detected metabolite (~84%). Regardless of survey cycle and the person's race/ethnicity or income, adjusted geometric mean concentrations of DCBA were higher in May-Sep than in Oct-Apr. Furthermore, non-Hispanic whites in the warm season were more likely than in the colder months [adjusted odds ratio (OR)=10.83; 95% confidence interval (CI), 3.28-35.79] and more likely than non-Hispanic blacks (OR=3.45; 95% CI, 1.51-7.87) to have DCBA concentrations above the 95th percentile. CONCLUSIONS: The general U.S. population, including school-age children, is exposed to DEET. However, reliance on DEET as the sole urinary biomarker would likely underestimate the prevalence of exposure. Instead, oxidative metabolites of DEET are the most adequate exposure biomarkers. Differences by season of the year based on demographic variables including race/ethnicity likely reflect different lifestyle uses of DEET-containing products.

On-line solid phase extraction-high performance liquid chromatography-isotope dilution-tandem mass spectrometry approach to quantify N,N-diethyl-m-toluamide and oxidative metabolites in urine.

Human exposure to N,N-diethyl-m-toluamide (DEET) occurs because of the widespread use of DEET as an active ingredient in insect repellents. However, information on the extent of such exposure is rather limited. Therefore, we developed a fast on-line solid phase extraction-high performance liquid chromatography-isotope dilution tandem mass spectrometry (HPLC-MS/MS) method to measure in urine the concentrations of DEET and two of its oxidative metabolites: N,N-diethyl-3-(hydroxymethyl)benzamide and 3-(diethylcarbamoyl)benzoic acid (DCBA). To the best of our knowledge, this is the first HPLC-MS/MS method for the simultaneous quantification of DEET and its select metabolites in human urine. After enzymatic hydrolysis of the conjugated species in 0.1 mL of urine, the target analytes were retained and pre-concentrated on a monolithic column, separated from each other and from other urinary biomolecules on a reversed-phase analytical column, and detected by atmospheric pressure chemical ionization in positive ion mode. The limits of detection ranged from 0.1 ng mL(-1) to 1.0 ng mL(-1), depending on the analyte. Accuracy ranged between 90.4 and 104.9%, and precision ranged between 5.5 and 13.1% RSD, depending on the analyte and the concentration. We tested the usefulness of this method by analyzing 75 urine samples collected anonymously in the Southeastern United States in June 2012 from adults with no known exposure to DEET. Thirty eight samples (51%) tested positive for at least one of the analytes. We detected DCBA most frequently and at the highest concentrations. Our results suggest that this method can be used for the analysis of a large number of samples for epidemiological studies to assess human exposure to DEET.

Quantification of riboflavin in human urine using high performance liquid chromatography-tandem mass spectrometry.

We developed a selective method to measure riboflavin in human urine. Sample preparation involved solid phase extraction and concentration of the target analyte in urine. The urine concentrate was analyzed using high performance liquid chromatography-tandem mass spectrometry. Riboflavin concentrations were quantified using an isotopically labeled internal standard. The limit of detection was 11 ng/mL, and the linear range was 4.4-20,000 ng/mL. The relative standard deviation at 100, 1000, and 5000 ng/mL was 17%, 17%, and 12%, respectively. The accuracy was 90%. On average, 100 samples, including calibration standards and quality control samples, were prepared per day. Using our method, we measured concentrations of riboflavin in human urine samples that were collected from participants in a study where riboflavin was used as a surrogate chemical to simulate exposure to an environmental toxicant.