Abstract:
The food contact paper products were cut into about 1 cm
2 of small pieces. The sample (10 g) was taken and placed into a stoppered triangular flask, and 200 mL of boiling water was added. The mixture was heated at 80 ℃ for 2 h. After cooling, the solution was diluted to 250 mL with water. 5.00 mL of the above solution was taken and placed into a test tube, and 0.05 mL of 10 mg · L
−1 mixed internal standard solution and 1 g of sodium chloride were added. After dissolution, the solution was passed through a diatomite solid-phase extraction cartridge, equilibrating for 10 min. Then the mixture was eluted with 18 mL of ethyl acetate, and the eluate was collected. 4 g of anhydrous sodium sulfate was added, and the mixture was settled for 10 min. The solution was filtered, and the filtrate was collected. The solution was blown to near dryness with nitrogen at 45 ℃, and the residue was dissolved in 2 mL of
n-hexane, and 0.04 mL of heptafluorobutyryl imidazole was quickly added. The mixture was vortexed for 30 s and derivatized in a electric hot blast drying oven at 70 ℃ for 30 min. After cooling to room temperature, 2 mL of 20% (mass fraction) sodium chloride solution was added. The mixture was vortexed for 1 min, allowed to stand for layering, and the upper layer solution was taken. 0.3 g of anhydrous sodium sulfate was added for drying, and the solution was filtered through a 0.22 μm nylon filter membrane. The 2 chloropropanols, including 1,3-dichloro-2-propanol (1,3-DCP) and 3-chloro-1,2-propanediol (3-MCPD) in the filtrate were determined by gas chromatography-tandem mass spectrometry. The derivatives of 1,3-DCP and 3-MCPD were separated on SH-Rxi-5Sil MS chromatographic column by programmed column temperature, ionized by electron impact ion source, detected in multiple reaction monitoring (MRM) mode, and quantified by isotope internal standard method. As shown by the results, linear relationships between the ratios of the corresponding derivative peak area to the internal standard derivative peak area and the ratios of mass concentrations 2 chloropropanols to their internal standards were found in the range of 0.5-200.0 μg · L
−1, with the same detection limits (3S/N) of 0.25 μg · L
−1. Test for recovery was made by the standard addition method, giving results in the range of 80.9%-116%, with RSDs (
n=7) of the determined values in the range of 0.58%-0.85%. This method was applied to analysis of 20 batches of food contact paper product samples, and both 1,3-DCP and 3-MCPD were detected, with the detection amounts in the range of 2.0-16 μg · L
−1 and 2.0-69 μg · L
−1, respectively. The release amounts of 1,3-DCP and 3-MCPD were higher when food contact paper products were exposed to higher contact temperatures and longer contact time with food.