Microcontaminants in pentachlorophenol synthesis. 1. New bioassay for microcontaminant quantification

We have refined and implemented a novel aryl hydrocarbon receptor capture bioassay for determining the toxic equivalent (TEQ) concentration of polychlorinated dibenzodioxins (PCDDs) and dibenzofurans (PCDFs) in pentachlorophenol samples. We calibrated the method for TEQ concentrations between 0.29 and 2.0 ppm. The standard deviation is typically about 20% of the reported value, but this value can be higher for samples with lower TEQ levels. Testing revealed that the single analysis of a sample is likely to be accurate to within +/- 40% of the reported value, with the uncertainty being attributable to random error. Performing multiple analyses of the same sample reduces the error considerably, to only a few percent. Applying this bioassay method to pentachlorophenol samples synthesized previously via an isothermal reaction provided TEQ concentrations for these samples. The results showed that the TEQ concentration in the samples increased as the synthesis temperature increased. Very high TEQ concentrations (9 ppm) were present in samples from synthesis at 188 degrees C, which points to the importance of keeping the temperature as low as possible during pentachlorophenol synthesis.