摘要：A method for the determination of low levels (∼10-11g/l) of benzo (α) pyrene (BaP) in raw water of water supply was studied. The water samples (1 or 31) were collected into a silanized erlenmeyer flask. Five g of Amberlite XAD-4 resin was added to the flask and mixed with magnetic stirrer for 5 h at 20°C in the dark. After the resin was filtered by a water aspirator, the resin was oven-dried at 50°C for 16 h. The resin was shaken with 20 ml of elution solvent, a mixture of ethanol and benzene (1 : 9, v/v), for 10 min by an ultrasonificator. The resin and the solvent were transferred to a 80 ml filter-funnel, and then the sorbed BaP on the resin was eluted with 100 ml of the elution solvent. The eluate was evaporated to dryness under a reduced pressure. The residual was dissolved in 0.5 ml of benzene. BaP in the benzene solution was separated by a one dimensional dual band thin-layer chromatography. The spots of BaP on the plate were scraped off into a small centrifugal tube. After adding 2 ml of dimethylsulfoxide (DMSO) into the tube, ultrasonic extraction was carried out for 10 min in order to dissolve BaP completely. The DMSO solution was centrifuged for 5 min, and then the supernatant was used for the identification and determination of BaP by a derivative spectrofluorometry. The determination was carried out under the following instrumental conditions ; excitation wavelength : 369 nm, slit 16 nm, emission wavelength : 380 nm scanning, slit 3.5 nm, order of derivative : 4-th, increment in differentiation : 3 nm, scanning speed : 60 nm/min. The recoveries by the presented method were at the 0.54 and 1.08 ng/l spiking levels of 11 distilled water for 85.6±4.5% and 84.2±3.7%, and at the 0.73 ng/l spiking levels of 31 real water sample for 82.2-97.3%, respectively. The sorbed BaP onto the resin was stable at 4°C or 20°C in the dark during 30 days. The losses of BaP by adsorption onto the inner walls of the erlenmeyer flask were 7% or less. When the determination of the concentration of BaP by this method was carried out, the lower limit of detection for 3 l water samples was 0.03 ng/l at the peak height of 2.5% levels of full-scale range. The concentrations of BaP in 6 ground water samples and 3 river water samples were determined by this method. It was confirmed that the concentrations in raw water of water supply were very small, ranging 0.05-0.15 ng/l.
