食品复合塑料包装材料中污染物萃取条件的优化

Optimization of Extraction Conditions of Pollutants in Food Composite Plastic Packaging Materials

目的研究以乙醇、甲醇、正己烷、丙酮、四氢呋喃为萃取剂,对4种复合塑料进行萃取,分析得出最佳的萃取剂、萃取时间、萃取温度、萃取剂用量等萃取工艺,并在该条件下检测复合塑料中污染物的含量。方法采用超声波技术对样品进行萃取,用气相色谱分析4种塑料制品中污染物的含量。结果通过扫描电镜观察超声萃取前后塑料制品的表面形貌,发现4种溶剂萃取后的塑料表面的形貌都发生了变化,正己烷、丙酮对塑料表面的影响尤为明显,都导致塑料表面溶胀发白,结合气相色谱测定的标准样品峰面积表明正己烷对标准样品的溶解度最好,因此最佳萃取剂为正己烷;在用正己烷萃取塑料制品的过程中,随着温度升高,萃取出来的污染物含量也增大,但当温度达到50℃后,增幅不再明显,因此最佳萃取温度为50℃;在最佳萃取温度下,正己烷的最佳萃取量为20 m L;最后测定塑料制品中污染物的含量,得出4种复合塑料中都存在一定量的污染物,且BHT的质量分数在0.0016%~0.11%之间,高于国家标准,污染物超标。结论用20 m L的正己烷在50℃下萃取20 min,其萃取效率最高;气相色谱测定数据显示4种复合塑料中都存在一定量的污染物。

The work aims to extract four kinds of composite plastics with ethanol, methanol, n-hexane, acetone and tetrahydrofuran as solvents, to obtain the best extraction process, including the extraction solvent, extraction time, extraction temperature and dosage of extraction solvent through analysis, and to detect the content of pollutants in composite plastics. The samples were extracted with ultrasonic technology, and the content of pollutants in four kinds of plastic products was analyzed with gas chromatography. The surface morphology of the plastic products before and after ultrasonic extraction was observed by scanning electron microscope. The surface morphology of the plastic was changed after being extracted with 4 kinds of solvents. But the effect of n-hexane and acetone on the plastic surface was obvious, and they both led to a swelling and whitish plastic surface. The peak area of the standard sample was measured in combination with gas chromatography and the results showed that： the solubility of standard samples was the best when the solvent was n-hexane, so the best extraction solvent was n-hexane. In the process of extracting plastic products with n-hexane, as the temperature rose, the content of the extracted pollutants was increased. But when the temperature reached 50 ℃, the increase was not obvious, so the optimum extraction temperature was 50 ℃. Under the optimum extraction temperature, the best extraction amount of n-hexane was 20 m L. Finally, the content of pollutants in plastic products was measured. It was concluded that a certain amount of pollutants existed in four kinds of composite plastics. The content range of BHT was 0.0016%~0.11%, higher than the national standard, and the pollutants exceeded the standard. The efficiency will be the highest when the extraction lasts for 20 min with 20 m L n-hexane at 50 ℃. The data measured with gas chromatographic show that a certain amount of pollutants exist in all the four kinds of composite plastics.