Urine samples from 197 Arkansas children were analyzed for eight chlorinated phenols and four chlorinated phenoxy herbicides by using a new procedure that combined gas chromatography with tandem mass spectrometry. With the detection limit of 1 part per billion (ppb), six of these pesticides were detected in more than 10% of the samples. 2,5-Dichlorophenol (a metabolite of p-dichlorobenzene), and pentachlorophenol were detected in 96% and 100%, respectively, of the children's urine at median concentrations of 9 ppb and 14 ppb, respectively. 2,4,5-Trichlorophenol was detected in 54% of the children's urine at a median concentration of 1 ppb. One trichlorophenol and three other dichlorophenols were found in 3% to 27% of the samples. The herbicide 2,4-dichlorophenoxyacetic acid was observed in 20% of all samples. The concentrations of all analytes are reported as background or reference levels for use in future studies. The finding of 2,5-dichlorophenol as a ubiquitous contaminant merits further study.

We have developed a method for determining selected chlorinated phenols and phenoxy herbicides in urine. The process of preparing the samples includes acid hydrolysis, extraction with benzene, derivatization with diazoethane, and column chromatography cleanup. We quantify the more volatile compounds by using capillary column gas chromatography/positive chemical ionization/mass spectrometry/mass spectrometry. Less volatile compounds are quantified by using electron capture negative chemical ionization in a single stage mass spectrometry mode. Quality control samples are included in each analytical run, and the results demonstrate that the analytical system is in control. Positive values for the target analytes are determined on the basis of appropriate relative retention time, a signal-to-noise ratio greater than 3:1, and a calculated concentration greater than 1 ppb. We determine the chlorine isotope ratios for each compound to assess the presence or absence of interferences. This analytical method has been applied in a case-control study of 199 individuals to examine exposure to the 12 target analytes.