在涂漆筷子食品接触部位截取横截面积为0.004 m²,长度为30 mm的小块样品,装入顶空瓶中,加入40 μL橄榄油并充入氮气,加盖密封并于80℃加热30 min,释放的气体以5∶1的分流比进入气相色谱仪,使用DB-624毛细管色谱柱在程序升温条件下分离目标物。设置载气流量为3.0 mL·min^-1,初始柱温为40℃,升温速率为2℃·min^-1。分离得到的目标物用带有电子轰击离子源的质谱仪,在选择离子监测模式下检测。结果显示:32种溶剂可在28 min内分离完全,工作曲线的线性范围为0.02~0.20 mg·m^-2(对二甲苯/间二甲苯)和0.01~0.10 mg·m^-2(其他30种溶剂),检出限(3S/N)为0.01 mg·m^-2(对二甲苯/间二甲苯)和0.005 mg·m^-2(其他30种溶剂);加标回收率为80.1%~118%,测定值的相对标准偏差(n=5)为1.2%~9.7%。方法用于20批实际样品的分析,酯类、醛类、醇类、酮类和苯类溶剂均有检出。为了消除样品中溶剂残留的影响,分别采用不同洗涤剂[1%(体积分数)洗洁精溶液、4%(体积分数)乙酸溶液和50%(体积分数,下同)乙醇溶液]于40℃浸泡30 min和高温(25~150℃)烘烤0~120 min的方法预处理新购样品。结果显示:用50%乙醇溶液浸泡后样品中的溶剂残留率(相对于水)均小于100%,低于其他2种洗涤剂的(相对于水);而120℃高温烘烤80 min所得样品中的溶剂残留率(相对于不烘烤)几乎为0,因此建议消费者在使用新购涂漆筷子前,先以此高温烘烤的条件预处理样品。

Small piece of the sample with cross-sectional area of 0.004 m² and length of 30 mm from the food contact part of the painted chopsticks was taken and put into an ampoule. 40 μL of olive oil was added, and the ampoule was filled with nitrogen. After sealing, the above mixture was heated at 80 ℃ for 30 min. The gases released were introduced into the gas chromatograph with a split ratio of 5∶1, and the targets were separated by using DB-624 capillary chromatographic column under the temperature programmed conditions, with carrier gas flow rate of 3.0 mL·min^-1, initial column temperature of 40 ℃ and heating rate of 2 ℃·min^-1. The separated targets were detected by the mass spectrometer with electron impact ion source and selective ion monitoring mode. It was shown that 32 solvents could be completely separated within 28 min, linear ranges of working curves were 0.02-0.20 mg·m^-2 (for m-xylene/p-xylene) and 0.01-0.10 mg·m^-2 (for the other 30 solvents), with detection limits (3S/N) of 0.01 mg·m^-2 (for m-xylene/p-xylene) and 0.005 mg·m^-2 (for the other 30 solvents). Results of test for the spiked recovery was in the range of 80.1%-118%, and RSDs (n=5) of the determined values ranged from 1.2% to 9.7%. The proposed method was applied to the analysis of 20 batches of actual samples, and esters, aldehydes, alcohols, ketones and benzene solvents were all detected. In order to eliminate the effect of solvent residues in samples, the newly purchased samples were pretreated by soaking in different detergents ［1% (volume fraction) detergent solution , 4% (volume fraction) acetic acid solution and 50% (volume fraction, the same below) ethanol solution］ at 40 ℃ for 30 min and by baking at high temperature (25-150 ℃) for 0-120 min, respectively. As found by the results, the solvent residue rates (relative to water) of targets in the sample soaked in 50% ethanol solution were below 100%, lower than those (relative to water) soaked in the other 2 detergents. The solvent residue rates (relative to no baking) in the samples obtained by high temperature baking at 120 ℃ for 80 min were almost 0, and it is suggested that consumers should pretreat the samples with the high temperature baking conditions before using newly purchased painted chopsticks.