Analytical performance of accelerator mass spectrometry and liquid scintillation counting for detection of ¹⁴C-labeled atrazine metabolites in human urine

Accelerator mass spectrometry (AMS) has been applied to the detection of ¹⁴C-labeled urinary metabolites of the triazine herbicide, atrazine, and the analytical performance of AMS has been directly compared to that of liquid scintillation counting (LSC). Ten human subjects were given a dermal dose of ¹⁴C-labeled atrazine over 24 h, and urine from the subjects was collected over a 7-day period. Concentrations of ¹⁴C in the samples have been determined by AMS and LSC and range from 1.8 fmol/mL to 4.3 pmol/mL. Data from these two methods have a correlation 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%. Factors limiting AMS detection limits for these samples and ways in which these can be improved are examined.