Comparison of immunoassay and gas chromatography/mass spectrometry methods for measuring 3,5,6-trichloro-2-pyridinol in multiple sample media

Two enzyme-linked immunosorbent assay (ELISA) methods were evaluated for the determination of 3,5,6-trichloro-2-pyridinol (3,5,6TCP) in multiple sample media (dust, soil, food, and urine). The dust and soil samples were analyzed by a commercial RaPID immunoassay testing kit. The food and urine samples were analyzed by a laboratory-based 96-microwell plate immunoassay format. Methanol was used as the extraction solvent for the preparation of the dust and soil samples for analysis by both the ELISA and gas chromatography/mass spectrometry (GC/MS) procedures. Chlorobutane was used for extraction of the urine samples for each method. The food samples were extracted with methanol for GC/MS and with acidic methanol for ELISA. The percent difference of the duplicate RaPID assays ranged from 0 to 43.4% for dust and from 0 to 47.9% for soil. The percent relative standard deviation of the 96-microwell plate triplicate assays was 15% or less for food and urine samples. Quantitative recoveries of 3,5,6-TCP were obtained for the spiked dust, soil, food and urine samples by ELISA ranging from 71 to 102%. Quantitative recoveries (>90%) of 3,5,6-TCP were also obtained for these samples by the GC/MS procedure. The overall method precision of these samples was within (plus-minus)10% using the GC/MS procedure. The immunoassay and GC/MS data were highly correlated, with correlation coefficients of 0.98 for dust, 0.98 for soil, 0.93 for food, and 0.98 for urine. Both ELISA methods can be used as quantitative monitoring tools for 3,5,6-TCP concentrations in dust, soil, food, and urine samples.