掺矿物油大米的定性分析方法研究

On Qualitative Analysis Method of Rice Mixed with Mineral Oil

采用皂化法、薄层色谱法以及红外光谱法对大米上是否涂抹液体石蜡的定性分析方法进行了研究。研究结果表明:采用索氏抽提法用乙醚从整粒大米中提取1g左右油脂,然后将油脂与氢氧化钾在体积分数95%的乙醇溶液中完全皂化,加入沸水后若溶液呈浑浊状态,则表明该种大米涂抹了石蜡;若透明,则表明没有涂石蜡。采用整粒米(50g)按上述方法也可以直接定性分析液体石蜡的存在。薄层色谱法可以有效地分析液体石蜡的存在。但是,红外光谱法则不能有效地鉴别出大米上是否含有液体石蜡。

The qualitative analysis method for determining the existence of liquid paraffin on rice by saponification method, thin-layer chromatography and infrared spectroscopy was studied. The study results showed that about 1 g oil was extracted from whole grain rice with ether by Soxtec extraction method and then the oil was saponified fully in 95% alcohol solution (volume fraction) with potassium hydroxide. The rice was coated with paraffin if the solution was cloudy after boiling water was added; otherwise, the solution was clear. Whole grain rice (50 g) can also be used to make direct qualitative analysis on the existence of liquid paraffin by above-mentioned method. Thin-layer chromatography can be used effectively to analyse the existence of liquid paraffin. However, infrared spectroscopy cannot be used to effectively determine the existence of liquid paraffin on rice.