Determination of 9 Indicative Polychlorinated Biphenyls in Surface Water and Groundwater by Gas Chromatography-Mass Spectrometry with Automatic Solid Phase Extraction

The 9 indicative polychlorinated biphenyls (PCBs) specified by GB/T 14848-2017 in surface water and groundwater were determined by the method mentioned by the title. Parameters of solid phase extraction column, water sample acidity, elution solvent and sampling flow were optimized. The surface water or groundwater sample was filled with a brown glass bottle, and its acidity was adjusted to pH 4. An aliquot (1 L) of the water sample was taken, and mixed with 50 mL of acetone. The mixed solution was put into a brown sample bottle, and passed through the activated Bond Elut C₁₈ solid phase extraction column with sampling flow of 10 mL·min^-1. The column was rinsed with 10 mL of water, and blown by nitrogen for 35 min. After the syringe pump was washed with 3 mL of methanol and 5 mL of n-hexane, the column was eluted with 7.5 mL of n-hexane and 7.5 mL of dichloromethane, and the eluent was collected and blown to nearly dry by nitrogen. The residue was mixed with the mixed internal standard solution of PCB77-d₆ and PCB156-2',6,6'-d₃, and diluted with n-hexane to 1.0 mL, making the mass concentration of each internal standard reach to 100 μg·L^-1. The obtained solution was introduced into gas chromatograph, and separated on HP-5MS chromatographic column under programmed temperature. The targets were detected by mass spectrometer equipped with an electron impact ion source, and quantitatively analyzed by internal standard method. As found by results that the linear ranges of the standard curves of the 9 PCBs were in the range of 1.0-200.0 μg·L^-1, with detection limits (3.143s) in the range of 1.1-2.2 ng·L^-1. Test for the spiked recovery was carried out on surface water and groundwater samples, and the 9 PCBs were not detected, giving recoveries in the ranges of 76.4%-102% (surface water) and 84.8%-106% (groundwater). The RSDs (n=6) of the determined values were found in the ranges of 0.21%-4.7% (surface water) and 0.64%-4.8% (groundwater).