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.