## Discussions on How to Improve the Comprehensive Innovation Abilities of Students by Designed Experiments: An Example of Simultaneous Determination of Vitamin C and E by Spectrophotometry

Wang Jingyu,1, Wang Heng1, Hui Xiong1, Chen Zhifei1, Yuan Hong2

 基金资助: 中央高校基本科研业务费.  2018KFYYXJJ120湖北高校省级教学研究项目.  2017095

Abstract

Simultaneous determination of vitamin C and vitamin E by spectrophotometry is a typical experiment of simultaneous determination of multiple components. However, the current experimental method has a large relative error (13.7%) in the determination of vitamin C. In this paper, according to the molecular structural characteristics of vitamin C and vitamin E, we studied the factors affecting the measurement accuracy of vitamin C and improve the experimental method by optimization pf design, and the error is reduced to 1.98%. Results proved that the improved method achieved higher accuracy, better reproducibility, more reliable results and better teaching responses. Through this designed experiment, the students are guided from many aspects such as aiming at practical problems and using theoretical knowledge to optimize the experimental scheme, therefore their comprehensive innovation abilities are improved.

Keywords： Simultaneous determination ; Vitamin C ; Vitamin E ; Spectrophotometry ; Comprehensive innovation ability

Wang Jingyu. Discussions on How to Improve the Comprehensive Innovation Abilities of Students by Designed Experiments: An Example of Simultaneous Determination of Vitamin C and E by Spectrophotometry. University Chemistry[J], 2020, 35(9): 76-82 doi:10.3866/PKU.DXHX201908025

### 1.1 仪器与试剂

#### 1.2.1 维生素C和维生素E系列标准溶液的配制

95%工业乙醇作为溶剂：将无水乙醇换成95%工业乙醇。其余步骤同上。

#### 1.2.4 待测样品液的配制

95%工业乙醇作为溶剂：将无水乙醇换成95%工业乙醇。其余步骤同上。

#### 1.2.5 待测样品中维生素C和E含量的测定

$A_{{\lambda _1}}^{{\rm{C}} + {\rm{E}}} = \varepsilon _{{\lambda _1}}^{\rm{C}}b{c_{\rm{C}}} + \varepsilon _{{\lambda _1}}^{\rm{E}}b{c_{\rm{E}}}$

$A_{{\lambda _2}}^{{\rm{C}} + {\rm{E}}} = \varepsilon _{{\lambda _2}}^{\rm{C}}b{c_{\rm{C}}} + \varepsilon _{{\lambda _2}}^{\rm{E}}b{c_{\rm{E}}}$

${c_{\rm{C}}} = \frac{{A_{{\lambda _1}}^{{\rm{C}} + {\rm{E}}}\varepsilon _{{\lambda _2}}^{\rm{E}} - A_{{\lambda _2}}^{{\rm{C}} + {\rm{E}}}\varepsilon _{{\lambda _1}}^{\rm{E}}}}{{\left( {\varepsilon _{{\lambda _1}}^{\rm{C}}\varepsilon _{{\lambda _2}}^{\rm{E}} - \varepsilon _{{\lambda _2}}^{\rm{C}}\varepsilon _{{\lambda _1}}^{\rm{E}}} \right)b}}$

${c_{\rm{E}}} = \frac{{A_{{\lambda _1}}^{{\rm{C}} + {\rm{E}}} - \varepsilon _{{\lambda _1}}^{\rm{C}}b{c_{\rm{C}}}}}{{\varepsilon _{{\lambda _1}}^{\rm{E}}b}}$

 测试条件 标准曲线 维生素C 维生素E λ1 λ2 λ1 λ2 无水乙醇 y = 0.0928x + 0.0265 (R2 = 0.9817) y = 0.0027x + 0.0646 (R2 = 0.5842) y = 0.0024x − 0.0001 (R2 = 0.9900) y = 0.0143x + 0.0002 (R2 = 0.9999) 无水乙醇加适量稀硫酸 y = 0.1075x + 0.0124 (R2 = 0.9995) y = −0.0006x + 0.0054 (R2 = 0.6452) y = 0.0032x − 0.0198 (R2 = 0.9876) y = 0.0143x − 0.0031 (R2 = 0.9999)

 溶剂 λ1处吸光度 λ2处吸光度 测试cC/(mg∙L−1) 测试cE/(mg∙L−1) cC相对误差/% cE相对误差/% 无水乙醇 0.3672 0.2398 3.54 16.10 13.65 40.01 无水乙醇加适量稀硫酸 0.4866 0.1634 4.18 11.60 1.98 0.89

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