EVALUATION OF THE GOULDEN LARGE-SAMPLE EXTRACTOR FOR ACIDIC COMPOUNDS IN NATURAL WATERS

摘要

The Goulden Large-Sample Extractor has received extensive use for monitoring and surveillance surveys of natural waters impacted by pulp and paper mills and agricultural runoff water. However, there are concerns'about whether this sampler, which was originally developed for extractions of hydrophobic polycyclic aromatic hydrocarbons', polychlorinated biphenyls, and other organochlorines, is suitable for sampling polar acidic compounds. The sampler was evaluated for recovery of surrogates for resin acids, fatty acids, herbicide acids, and chlorophenols from natural waters. Performance tests conducted in this work indicated that three surrogate compounds with K_p (C_(DCM)/C_(water pH 2)) values from 16,700 to 1,260 were extracted from pH 2-adjusted 20-L water samples with an average recovery of 83.6%. The surrogate compounds with K_p values less than 1,000 were extracted with significantly lower recoveries. The variability ranged from 10 to 36% relative standard deviation. Recoveries and variability compared favorably with reported recoveries and variabilities for neutral pesticide surrogates. Specific performance criteria (percent recoveries ± standard deviation, number of determinations in parentheses) observed for the surrogates 2,4,6-tribrom-ophenol, heptadeeanoic acid, O-methylpodocarpic acid, dichlorophenylacetic acid, and 4-bromophenol were 89.5 ± 24.0 (17), 82.8 ± 21.7 (18), 78.4 ± 14.8 (18), 41.9 ± 8.5 (16), and 22.1 ± 8.1 (19), respectively. Low recoveries of the 4-bromophenol surrogate may be due in part to side reactions with diazomethane. As a result, 4-bromophenol is not recommended as a surrogate. These values can be used to provide guidelines for acceptable surrogate recoveries and validation of extractions of polar acidic compounds.