Determination of Residues of 6 Common Flame Retardants in Soil Around Chemical Enterprises by Ultra-High Performance Liquid Chromatography-Triple Quadrupole Mass Spectrometry with Fully Automatic Accelerated Solvent Extraction

The title method was established to determine the 6 common flame retardants in the soil around chemical enterprises, including trimethyl phosphate, triethyl phosphate, triphenyl phosphate, hexabromocyclododecane, decabromodiphenyl ether and isocyanurate. After sample was removed, crushed, dried and sieved, an aliquot (10.0 g) was taken, and mixed with about 10 g of diatomite. The mixture was placed into the fully automatic accelerated solvent extractor, and extracted by the set procedure. The extract was blown to 5 mL by nitrogen, and passed through the C₁₈ solid phase extraction column activated beforehand. After rinsing, the column was eluted with 10 mL of mixed solution composed of acetone and cyclohexane at volume ratio of 1∶1. The eluent was collected, and blown to nearly dryness by nitrogen at 60 ℃. The residue was diluted to 1 mL with cyclohexane, and the solution was passed through a 0.45 μm filter membrane. The filtrate was analyzed according to the optimized working conditions of the instrument, with the UPLC BEH-C₁₈ column as the stationary phase, and the mixed solutions composed of acetonitrile and 10 mmol·L^-1 ammonium formate solution at different volume ratios as the mobile phase for gradient elution. Each target was ionized by positive ion mode of electric spray ion source, and detected by multiple reaction monitoring mode. It was shown that linearity relationships between values of the mass concentration and the peak area of each target were kept in the same range of 0.01-10.00 mg·L^-1, with detection limits (3S/N) in the range of 0.061-0.143 μg·kg^-1. The spiked recovery test was made on the blank sample at concentration levels of 0.01, 0.50, 10.00 mg·L^-1, giving recoveries in the ranges of 57.1%-80.2%, 81.2%-90.5% and 83.7%-92.8%, respectively. Six parallel tests were made, and RSDs of the determined values were found in the range of 2.0%-4.2%. The proposed method was applied to the analysis of 6 actual samples, and trimethyl phosphate, triethyl phosphate, triphenyl phosphate, hexabromocyclododecane and isocyanurate were detected, with detection amounts in the range of 5.63-214.60 μg·kg^-1.