可视化移动反应界面滴定法测定豆浆中蛋白质的含量

Determination of total protein content in soya-bean milk via visual movingreaction boundarytitration

利用移动反应界面滴定（moving reaction boundary titration,MRBT）技术可视化快速准确测定豆浆中的总蛋白质含量.在MRBT中,移动反应界面（moving reaction boundary,MRB）是由阴极液中的氢氧根离子和固定在聚丙烯酰胺凝胶（polyacrylamide gel,PAG）中的豆浆蛋白质分子形成,通过酸碱指示剂来指示MRB的移动.利用MRB移动速度（VMRB）与蛋白质浓度存在的函数关系建立标准曲线.配对t检验MRBT测定结果与凯氏定氮相比在95％的置信区间内无显著性差异.MRBT测定所需时间为10 min左右,线性范围为2.0 ～14.0 g/L,检出限为0.05 g/L,日内相对标准偏差小于1.90％,日间相对标准偏差小于4.39％,回收率为97.41％ ～99.91％.此外,三聚氰胺等非蛋白质氮（non-protein nitrogen,NPN）的添加,对豆浆中蛋白质的测定结果影响较小.

A visual,rapid and accurate moving reaction boundary titration （MRBT） method was used for the determination of the total protein in soya-bean milk.During the process,moving reaction boundary （MRB） was formed by hydroxyl ions in the catholyte and soya-bean milk proteins immobilized in polyacrylamide gel （PAG）,and an acid-base indicator was used to denote the boundary motion.The velocity of MRB has a relationship with protein concentration,which was used to obtain a standard curve.By paired t-test,there was no significant difference of the protein content between MRBT and Kjeldahl method at 95% confidence interval.The procedure of MRBT method required about 10 min,and it had linearity in the range of 2.0-14.0 g/L,low limit ofdetection （0.05 g/L）,good precision （RSD of intra-day 〈 1.90% and inter-day 〈4.39%）,and high recoveries （97.41%-99.91%）.In addition,non-protein nitrogen （NPN） such as melamine added into the soya-bean milk had weak influence on MRBT results.