“食品中的铁元素检验”教学实验条件的优化

Optimization of Teaching Experiment Conditions of “Inspection of Iron in Food”

2019年人教版普通高中化学必修一新增了"检验食品中的铁元素"实验,按照该实验方案检测菠菜中的铁元素,由于色素干扰不能观察到明显的实验现象。鉴于此,采用提取液显色后的色度透过率作为评价指标,以控制变量法为实验方法,对常见含铁食品、铁元素提取方法、提取时间、提取剂中盐酸浓度和提取剂用量等条件进行了研究和优化。优化后的实验结果表明:采用2 g豆筋、20 mL浓度为4 mol/L的盐酸、破壁机搅拌提取5 min后的提取液显色,其色度值为62%,显示很明显的血红色。此实验方案能够有效证明食品中铁元素的存在,具有明显的实验现象,能应用于教师演示实验和学生分组实验。

The "inspection of iron in food" experiment has been added to the 2019 People’s Education Edition senior high school chemistry textbook compulsory one, according to this experimental scheme, iron in spinach was detected, but experimental phenomena could not be observed obviously due to pigment interference. In view of this, the color transmittance of the extraction solution after color development was used as the index to evaluate the experimental effect, and the control variable method was used as the experimental method. The common iron-containing food, iron extraction method, extraction time, concentration of hydrochloric acid in the extraction agent and the amount of the extraction agent were optimized. The optimized experimental results showed that 2 g bean tendon and 20 mL hydrochloric acid with the concentration of 4 mol/L were stirred by the wall-breaking machine and extracted for 5 min, and the color value of the extract was 62%, showing a good blood red. It can effectively prove the existence of iron in food and has obvious experimental phenomenon. It can be well applied to teachers’ demonstration experiments and students’ group experiments.