Determination of Nonylphenol in Tile Grouts by Gas Chromatography- Mass Spectrometry with Ultrasonic Extraction

The tile grout sample was incubated, frozen overnight, and ground into particles with particle size of not more than 1 mm. An aliquot (2.0 g) of the sample was taken, and 50 mL of n-hexane was added. The mixture was extracted under 400 W ultrasound power in 40 ℃ water bath for 1 h. The extract was dried by anhydrous sodium sulfate, and evaporated to 1 mL by rotating at 35 ℃, all of which passed through the HLB solid phase extraction column. Elution was carried out by 5 mL of acetone, 5 mL of mixed solution composed of acetone and n-hexane at volume ratio of 1∶1 and 5 mL of n-hexane, and all the eluate was collected, blown to near dryness by nitrogen, and diluted to 1 mL by n-hexane. The resulting solution was analyzed by gas chromatograph-mass spectrometer. Nonylphenol was separated on the HP-5MS chromatographic column as the stationary phase, ionized by electron impact ion source, and quantified by external standard method. As found by the results, the retention time of 12 nonylphenol isomers was found in the range of 7.8-8.6 min, and linear relationship between values of the mass concentration of nonylphenol and the sum of peak areas of quantitative ions (m/z 107, 121, 135, 149, 163) was kept in the range of 0.3-5.0 mg·L^-1, with detection limit (3S/N) of 0.05 mg·kg^-1. Test for recovery was made by standard addition method, giving recoveries in the range of 88.4%-98.6%, and RSDs (n=6) of the determined values ranged from 2.7% to 11%. The proposed method was applied to the analysis of 8 tile grout samples from the market, nonylphenol was detected in 1 sample, with detection amount of 0.21 mg·kg^-1.