Analytical Performance of Accelerator Mass Spectrometry and Liquid Scintillation Counting for Detection of 14 C-Labeled Atrazine Metabolites in Human Urine S. Douglass Gilman,* ,² Shirley J. Gee, and Bruce D. Hammock Departments of Entomology and Environmental Toxicology, University of California, Davis, California 95616 John S. Vogel, Kurt Haack, Bruce A. Buchholz, and Stewart P. H. T. Freeman Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94551 Ronald C. Wester, Xiaoying Hui, and Howard I. Maibach Department of Dermatology, University of California, San Francisco, California 94143 Accelerator mass spectrometry (AMS) has been applied to the detection of 14 C-labeled urinary metabolites of the triazine herbicide, atrazine, and the analytical perfor- mance of AMS has been directly compared to that of liquid scintillation counting (LSC). Ten human subjects were given a dermal dose of 14 C-labeled atrazine over 2 4 h, and urine from the subjects was collected over a 7 -day period. Concentrations of 14 C in the samples have been deter- mined by AMS and LSC and range from 1.8 fmol/ mL to 4.3 pmol/ mL. Data from these two methods have a corre- lation coefficient of 0.998 for a linear plot of the entire sample set. Accelerator mass spectrometry provides superior concentration (2.2 vs 27 fmol/ mL) and mass (5.5 vs 54 000 amol) detection limits relative to those of LSC for these samples. The precision of the data provided by AMS for low-level samples is 1.7%, and the day-to-day reproducibility of the AMS measurements is 3.9%. Fac- tors limiting AMS detection limits for these samples and ways in which these can be improved are examined. More than 70 million pounds of the triazine herbicide, atrazine (Figure 1), are applied annually in the United States to agricultural lands. 1 Low-level human exposure to atrazine is likely to occur, especially to agricultural workers and to people utilizing water- sheds that drain agricultural areas subject to heavy atrazine application. 2-4 Although atrazine exhibits very low acute toxicity 4,5 and has been found to be nonmutagenic in most studies, 4,6,7 there is concern about human exposure to atrazine based on a study that found that high chronic doses of atrazine increased the incidence of mammary tumors in female Sprague-Dawley rats. 4,8 An immunoassay-based method to monitor human exposure to atrazine has been developed and has been shown to be capable of detecting atrazine exposure in pesticide applicators. 9 Our primary interest in atrazine is as an indicator of work practice as related to general agrochemical pesticide exposure. We selected atrazine because of its exceptionally low toxicity to mammals and its widespread use. The metabolism and excretion of triazine herbicides have been well studied in test animals 10-16 and, less commonly, in vitro with * Corresponding author. Fax: (423) 974-3454. E-mail: sdgilman@ utk.edu. † Current address: Department of Chemistry, University of Tennessee, Knoxville, TN 37996-1600. (1) Gianessi, L. P.; Anderson, J. E. Pesticide Use in U.S. Crop Production; National Center for Food and Agricultural Policy: Washington, DC, 1995. (2) Solomon, K. R.; Baker, D. B.; Richards, R. P.; Dixon, K. R.; Klaine, S. J.; La Point, T. W.; Kendall, R. J.; Weisskopf, C. P.; Giddings, J. M.; Giesy, J. P.; Hall, L. W., Jr.; Williams, W. M. Environ. Toxicol. Chem. 1996 , 15, 31-76. (3) Kolpin, D. W.; Thurman, E. M.; Goolsby, D. A. Environ. Sci. Technol. 1996 , 30, 335-40. (4) Environmental Protection Agency. Fed. Regist. 1994 , 59, 60412-43. (5) Stevens, J. T.; Sumner, D. D. In Handbook of Pesticide Toxicology; Hayes, W. J., Laws, E. R., Eds.; Academic Press: New York, 1991; Vol. 3, pp 1381-3. (6) Brusick, D. J. Mutat. Res. 1994 , 317, 133-44. (7) Sathiakumar, N.; Delzell, E.; Cole, P. Am. J. Ind. Med. 1996 , 29, 143-51. (8) Mayhew, D. A.; Taylor, G. D.; Smith, S. H.; Banas, D. A. Twenty-Four Month Combined Chronic Oral Toxicity and Oncogenicity Study in Rats Utilizing Atrazine Technical; Study No. 410-1102, Accession No. 262714-252727, Conducted by American Eiogenics Corp. for Ciba-Geigy Corp., 1986. (9) Lucas, A. D.; Jones, A. D.; Goodrow, M. H.; Saiz, S. G.; Blewett, C.; Seiber, J. N.; Hammock, B. D. Chem. Res. Toxicol. 1993 , 6, 107-16. (10) Adams, N. H.; Levi, P. E.; Hodgson, E. J. Agric. Food Chem. 1990 , 38, 1411- 7. (11) Bakke, J. E.; Larson, J. D.; Price, C. E. J. Agric. Food Chem. 1972 , 20, 602- 7. Figure 1. Structure of atrazine, 6-chloro-N-ethyl-N′-(1-methylethyl)- 1,3,5-triazine-2,4-diamine. The test compound for this study was labeled with 14 C at the three ring carbons as indicated by asterisks. Anal. Chem. 1998, 70, 3463-3469 S0003-2700(97)01383-8 CCC: $15.00 © 1998 American Chemical Society Analytical Chemistry, Vol. 70, No. 16, August 15, 1998 3463 Published on Web 07/11/1998