Determination of pentachlorophenol in wastewater irrigated soils and incubated earthworms

The analyses of low pentachlorophenol (PCP) in soils and earthworms require a sensitive and reliable analytical method. In this paper, several derivatization methods and extraction solvents were compared systematically. The derivatization reagents included acetic anhydride, 2,3,4,5,6-pentafluorobenzyl bromide (PFBBr) and diazomethane. Hexane, acetone, hexane–acetone (1:1), dichloromethane and methanol were used as the extraction solvents. PFBBr derivatization showed the highest sensitivity. The derivatization parameters of PFBBr including the amount of PFBBr, the power and irradiation time of microwave were optimized. As a result, 200 μl of PFBBr (10%) at 150 W of microwave oven for 30 min achieved the best result. The PFBBr derivatization method had the detection limit of 0.07 μg l−1 of PCP. Extraction by a mixture of hexane and acetone (1:1) showed the best recoveries. The recommended method was used to determine the low PCP in soils irrigated by wastewater and earthworms incubated in the corresponding soils. The concentrations of PCP in soils were in the range of 1.38–179 ng g−1, while those in earthworms were 11.2–262 ng g−1. The recoveries of the surrogate standard (trichlorophenol) ranged from 81.1% to 107%, demonstrating the merit of the method.