【摘要】 目的测定硫普罗宁水溶液氧化反应的速率常数和反应级数。方法在一定温度下,向反应溶液中持续通入空气以维持溶解氧浓度恒定,利用氧电极测定氧的浓度。采用碘量法测定硫普罗宁在水溶液中不同时刻的浓度,计算氧化反应降解速率常数。结果试验温度下,在pH=4.0和pH=6.8的缓冲溶液中,硫普罗宁与氧的反应均为表观零级反应,293.2 K时平均表观反应速率常数分别为(8.08±0.12)×10-6mol.L-1.h-1和(7.53±0.06)×10-5mol.L-1.h-1;而在pH=9.0的缓冲溶液中,293.2 K时硫普罗宁与氧的反应为表观一级反应,平均表观反应速率常数为(2.12±0.05)×10-2h-1。结论在弱酸性和中性条件下反应速率较慢,抗氧化能力较强;在弱碱性条件下反应速率较快,抗氧化能力较弱。在硫普罗宁溶液的初始浓度及pH值相同的条件下,温度升高,表观反应速率常数增大。更多还原

【Abstract】 Objective To determine the oxidation reaction rate constant of Tiopronin in aqueous solution.Methods A sufficient air was inflated into the solution continually to keep the concentration of dissolved oxygen steady.The concentration of dissolved oxygen was determined by the electric potential method.The residual concentration of Tiopronin in the solution was measured with the iodimetry.The reaction rate constant could be obtained from a linear regression method.Results In weak acid and neutral buffer solutions,the degradation of Tiopronin conformed to zero-order kinetics at all experimental temperatures.The apparent rate constants at 293.2 K were(8.08±0.12)×10-3 mmol·L-1·h-1 and(7.53±0.06)×10-2 mmol·L-1·h-1,respectively.In the weak alkaline solution,the degradation conformed to first-order kinetics.The apparent rate constant at 293.2 K was(2.12±0.05)×10-2 h-1.Conclusion Results show that Tiopronin possesses stronger antioxidant activity in weak acid and neutral solutions than in the weak alkaline solution.Under the same initial concentration and pH value,the higher the temperature is,the larger the apparent rate constant will be.更多还原