维生素C和焦亚硫酸钠与溶解氧反应机理的探讨

目的:确定维生素C溶液中维生素C和抗氧剂焦亚硫酸钠与溶解氧的反应机理。方法:将维生素C和焦亚硫酸钠分别于敞开容器中进行试验,分别测定其降解动力学参数,求得其降解速率常数。再将维生素C和焦亚硫酸钠混合,在敞开容器中试验,分别测定其降解动力学参数,求得其降解速率常数。结果:维生素C和焦亚硫酸钠在敞开容器中都为表观零级降解,其降解速率常数分别为:kA,ap=2.2×10-3(mol·L-1·h-1)和kB,ap=1.12×10-4(mol·L-1·h-1)。维生素C和焦亚硫酸钠混合时,其降解速率常数分别为:kA,ap=2.0×10-3(mol·L-1·h-1)和kB,ap=1.13×10-4(mol·L-1·h-1)。当在维生素C溶液中加入焦亚硫酸钠时,两者的降解速率常数几乎不变,表明维生素C和焦亚硫酸钠同时与氧气进行反应。结论:维生素C溶液中,维生素C和焦亚硫酸钠与氧气的反应同时进行,为平行反应。

Determination of the reaction mechanism of ascorbic acid and sodium metabisulfite with oxygen

Objective:To determine the mechanism of the reaction of ascorbic acid and sodium metabisulfite with the dissolved oxygen in the solution. Methods: The degradation of ascorbic acid and sodium metabisulfite under exposed atmosphere condition were investigated,respectively. The degradation of ascorbic acid and sodium metabisulfite in their mixed solution were also investigated, respectively. Results: Both of the reaction order with respect to ascorbic acid and sodium metabisulfite were apparent zero -order reaction. The apparent rate constants were k A,ap =2.2×10 -3 (mol·L -1 ·h -1 )and k B,ap =1.12×10 -4 (mol·L -1 ·h -1 )for ascorbic acid and sodium metabisulfite,respectively,when the experiments were run separately. And the apparent rate constants were k A,ap =2.0×10 -3 (mol·L -1 · h -1 )and k B,ap =1.13×10 -4 (mol·L -1 ·h -1 )for ascorbic acid and sodium metabisulfite,respectively,in their mixed solution. The values of the rate constants for ascorbic acid and sodium metabisulfite in the two sets of experiments were almost same,respectively. Conclusion: The results suggesting that the reaction mechanism of ascorbic acid and sodium metabisulfite with oxygen was a parallel reaction.