基于K_3[Fe(CN)_6]选择性氧化自动永停滴定法同时测定胱氨酸和半胱氨酸

Determination of cysteine and cystine with automatic dead stop titration based on selective oxidation reaction promoted by K_3[Fe(CN)_6]

目的构建基于K_3[Fe(CN)_6]选择性氧化自动永停滴定法同时测定胱氨酸和半胱氨酸的新方法。方法以K_3[Fe(CN)_6]为滴定剂,永停滴定法同时测定药剂中半胱氨酸和胱氨酸,设定极化电压50 m V、电流计灵敏度10-9A、门限值60%。结果对仪器滴定参数、试样分解、滴定时酸度、试剂用量、测定范围、共存元素影响等分析条件进行了实验优化。该法滴定终点突跃明显,半胱氨酸和胱氨酸检出限为0. 01 mmol/L,平均回收率分别为97. 28%和98. 73%,RSD为0. 27%和0. 56%。结论 K_3[Fe(CN)_6]符合基准物质要求,可直接配制滴定液,安全可靠,易保存;方法简便、快捷、灵敏、准确。

Objective To establish a new method for detection of cysteine and cystine with automatic dead stop titration based on selective oxidation reaction promoted by K3[Fe( CN)6]. Methods With K3[Fe( CN)6] as titrant,cysteine and cystine were detected with automatic dead stop titration. The polarized voltage was set at 50 m V,and the sensitivity was set at 10^-9A.The threshold value was set at 60 scale. Results The analysis conditions were optimized with instrumental titration parameters,sample decomposition,titration acidity,reagent dosage,determination range,coexisting elements. The titration end point of this method was obvious,and the detection limits of cysteine and cystine was 0. 01 mmol/L,the recovery rates were 97. 28% and98. 73%. The RSDs were 0. 27% and 0. 56%. Conclusion K3[Fe( CN)6]was in accordance with the requirements of standard substance,and it can be directly used to prepare titrant,which is safe,reliable and easy to save. This method is simple,rapid,sensitive and accurate.