Measurement of additive residues in food contact materials is important for safety monitoring at the initial stage. Most of the current studies focus on the determination of the migration amounts of chemical hazards from food contact materials into food simulants. Studies on chemical hazard residues in food contact materials are limited to monomers, oligomers, heavy metals, phthalic acid esters, and biphenols, which are known environmental pollutants. Only a few studies have investigated analysis methods for additive residues in food contact materials. In this study, the main factors (monitoring wavelength, chromatographic column, mobile phase, extraction solvent, etc.) that affect the accuracy and sensitivity of eight compounds, including three antioxidants, three light stabilizers, and two plasticizers, were investigated during sample preparation and instrument analysis. A method based on ultrahigh-performance liquid chromatography (UPLC) was developed for the simultaneous determination of these eight additives in polyethylene (PE). The PE food contact material sample was ground to homogenize the particle sizes under freeze-grinding. After comparing the extraction efficiencies of methylbenzene, chloroform, acetone, and acetonitrile, 2.0 g of the sample was extracted with methylbenzene at 80 ℃ and 10.34-11.72 MPa (1500-1700 psi) by accelerated solvent extraction (ASE) for 10 min once. The exaction solvent (10 mL) was transferred and concentrated to near dryness under a gentle stream of nitrogen gas and then re-dissolved in 10 mL of the initial mobile phase (70% (v/v) methanol in water). Finally, the eight compounds were analyzed by UPLC. After optimization of the analytical column and mobile phases, the eight analytes were separated on an ACQUITY UPLC BEH C8 chromatographic column (100 mm×2.1 mm, 1.7 μm) by gradient elution using water and acetonitrile as the mobile phases. The column oven temperature, flow rate of the mobile phase, and injection volume were 30 ℃, 0.3 mL/min, and 5 μL, respectively. The analytes were detected by a diode assay detector (DAD) in the scanning range of 210 nm to 400 nm. The monitoring wavelength was set at 230 nm, 250 nm, 280 nm, and 330 nm. External standard calibration curves were used for quantification. Under the optimized conditions, the calibration curves for the eight compounds showed good linearity in the range of 0.2 μg/mL to 10 μg/mL, and the correlation coefficients were >0.999. The recoveries in spiked blank polyethylene samples at the level of 0.05% were in the range of 83.8% to 103.4%, with relative standard deviations (RSDs) ranging from 0.14% to 7.86%. To validate the method, PE reference materials containing these eight compounds were manufactured at the content level of 0.2% to 0.9%. The recoveries using the prepared reference materials ranged from 63.5% to 118.5%, and the RSDs were in the range of 4.61% to 15.6%. The limits of detection (LODs, S/N=3) of all the eight compounds were 0.005% and the limits of quantification (LOQs, S/N=10) were 0.02%, in compliance with the current legislation. To assess the feasibility and potential of the proposed approach for routine analyses of these eight compounds, the developed method was applied to the analysis of these compounds in ten PE food packages and PE gloves. In six samples, tris(2,4-di-tert-butylphenyl)phosphite (Irganox 168) was detected at a level of 0.02%-0.07%, which was lower than the maximum level of this compound in PE food contact material products regulated in GB 9685-2016 at 0.2%. The method is compliant with the current legislation, and it can be used for the monitoring and supervision of these eight additives in PE food contact materials.
食品接触材料中添加剂残留量的测定为食品接触材料从源头进行安全监管具有重要意义。然而目前的大多数研究只针对食品接触材料中有害物迁移量的测定,对于食品接触材料中有害物含量的测定方法仅局限于残留单体、低聚体、重金属,以及邻苯二甲酸酯类、双酚类化合物等环境污染物,对食品接触材料中添加剂残留量的测定较少。该研究系统地优化了样品前处理过程及仪器分析中影响8种添加剂分析准确度与响应灵敏度的各主要因素,建立了超高效液相色谱同时测定聚乙烯材料中8种添加剂的定量分析方法。聚乙烯样品冷冻研磨后,取2.0 g样品采用甲苯作为萃取溶剂,80 ℃, 10.34~11.72 MPa (1500~1700 psi)下对其进行加速溶剂萃取,取10 mL上清液,氮气吹干后用10 mL初始流动相(甲醇-水,7∶3, v/v)定容。采用ACQUITY UPLC BEH C8色谱柱(100 mm×2.1 mm, 1.7 μm)进行分离,柱温30 ℃,进样量5 μL,以乙腈和水作为流动相进行梯度洗脱,流速0.3 mL/min,二极管阵列检测器(DAD)在210~400 nm范围内扫描,230、250、280、330 nm监测,外标法定量。8种目标物在0.2~10 μg/mL质量浓度范围内线性关系良好,相关系数(R 2)>0.999。空白聚乙烯样品添加含量为0.05%时,加标回收率在83.8%~103.4%之间,RSD在0.14%~7.86%之间。对于含量为0.2%~0.9%之间的质控样品,8种目标物的平均回收率在63.5%~118.5%之间,RSD在4.61%~15.6%之间。8种目标物的定量限为0.02%。应用该方法测定10份市售聚乙烯食品包装袋和手套,其中6份样品均检测出含有亚磷酸三(2,4-二叔丁苯基)酯(抗氧剂168),含量为0.02%~0.07%,均小于GB 9685-2016规定的聚乙烯类食品接触材料中抗氧剂168的最大使用量(0.2%)。该方法能够满足聚乙烯类产品中8种添加剂的分析要求,可用于食品接触材料风险监测。
Keywords: additive; food contact material; polyethylene (PE); ultrahigh-performance liquid chromatography (UPLC).