Determination of N-Methylpyrrolidone in Food Packaging Paper by Gas Chromatography-Mass Spectrometry with Freeze Grinding and Headspace

A method for determination of N-methylpyrrolidone (NMP) in food packaging paper by gas chromatography-mass spectrometry with freeze grinding and headspace was proposed. The food packaging paper sample was frozen and ground, and 1 g of ground sample was taken and placed in a 20 mL-headspace vial. 1 mL of glycerol triacetate was added, and 100 µL of 1 g·L⁻¹ NMP-d₉ internal standard solution was added. The mixture was separated on a HP-INNOWAX chromatographic column according to the column heating program. Selected ion monitoring (SIM) mode was adopted in mass spectrometry analysis, and the matrix matching method was used for quantitative analysis. As shown by the results, linear relationship between the ratios of the corresponding peak area to the internal standard peak area and mass fractions of NMP was kept in the range of 5-500 mg·kg⁻¹, with detection limit (3S/N) of 1.07 mg·kg⁻¹. Test for recovery was made by the standard addition method, giving results in the range of 98.8%-100%, with RSDs (n=6) of the determined values less than 2.0%. This method was used for the analysis of 36 samples of food packaging paper, and NMP in 15 samples was detected, with detection amounts in the range of 26.3-351.0 mg·kg⁻¹.