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    酶催化-库仑滴定法快速测定烟草制品中葡萄糖的含量

    Rapid Determination of Glucose in Tobacco Products by Coulometric Titration with Enzymatic Catalysis

    • 摘要: 取处理过的烟草制品样品1.000 0 g,加入20 mL水,于30 ℃振荡萃取1 h,过定性滤纸,用0.1 mol·L−1乙酸溶液调节滤液pH至5.8,加入20 mL 0.05 mol·L−1乙酸盐缓冲液(pH 5.8),于37 ℃预热10 min,再加入1 mL 2.0 g·L−1葡萄糖氧化酶溶液,于37 ℃反应20 min,加入2 mL 0.10 mol·L−1氢氧化钠溶液,混匀,用水定容至50 mL。基于葡萄糖氧化酶催化氧化葡萄糖生成葡萄糖酸-δ-内酯和过氧化氢的反应,提出了两种库仑滴定法。酸碱库仑滴定法以0.6 mol·L−1氯化钾溶液作电解质溶液,在20.0~50.0 mA电流下电解产生H+滴定样品溶液中过量的OH;氧化还原库仑滴定法以0.8 mol·L−1硫酸亚铈溶液作电解质溶液,在1.0~5.0 mA电流下电解生成Ce4+滴定样品溶液中过氧化氢。两种方法均通过到达滴定终点的电解时间(即滴定时间),根据法拉第电解定律测定烟草制品样品中葡萄糖的含量。结果显示,葡萄糖的质量浓度在50.0~800.0 mg·L−1内与对应的滴定时间呈线性关系,酸碱库仑滴定法的检出限(3s)为2.04 mg·L−1,氧化还原库仑滴定法的检出限(3s)为3.13 mg·L−1。按照标准加入法进行回收试验,回收率为98.1%~103%,测定值的相对标准偏差(n=5)均小于2.0%。方法用于实际样品的分析,葡萄糖的测定结果与YC/T 447—2012中高效液相色谱-蒸发光散射检测器法测定结果相比较,无显著性差异。

       

      Abstract: The treated tobacco product sample (1.000 0 g) was taken, and 20 mL of water was added. The mixture was shaken and extracted at 30 ℃ for 1 h, then filtered through qualitative filter paper. The pH of the filtrate was adjusted to 5.8 with 0.1 mol·L−1 acetic acid solution. 20 mL of 0.05 mol·L−1 acetate buffer solution (pH 5.8) was added, and the solution was preheated at 37 ℃ for 10 min. Then 1 mL of 2.0 g·L−1 glucose oxidase solution was added, and the solution was reacted at 37 ℃ for 20 min. 2 mL of 0.10 mol·L−1 sodium hydroxide solution was added, the mixture was mixed thoroughly, and the volume was made up to 50 mL with water. Based on the reaction in which glucose is catalytically oxidized by glucose oxidase to produce gluconic acid-δ-lactone and hydrogen peroxide, two coulometric titration methods were proposed. For the acid-base coulometric titration, 0.6 mol·L−1 potassium chloride solution was used as the electrolyte solution. H+ was electrolytically generated under a current of 20.0−50.0 mA for the titration of excess OH in the sample solution. For the redox coulometric titration, 0.8 mol·L−1 cerous sulfate solution was used as the electrolyte solution. Ce4+ was electrolytically generated under a current of 1.0−5.0 mA for the titration of hydrogen peroxide in the sample solution. The glucose in tobacco product samples was determined in both methods by measuring the electrolysis time required to reach the titration endpoint (i.e., the titration time) according to Faraday's law of electrolysis. As shown by the results, linear relationship between the corresponding titration time and mass concentrations of glucose was kept in the range of 50.0‒800.0 mg·L−1. The detection limit (3s) of the acid-base coulometric titration method was 2.04 mg·L−1, and detection limit (3s) of the redox coulometric titration method was 3.13 mg·L−1. Test for recovery was made by the standard addition method, giving results in the range of 98.1%−103%, with RSDs (n=5) of the determined values less than 2.0%. This method was applied to the analysis of actual samples, and there was no significant difference in the determination results of glucose between this method and high performance liquid chromatography-evaporative light scattering detector method in YC/T 447—2012.

       

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