Abstract: A new method of high-purity calcium citrate synthesized by using an on-line cation-resin column was proposed,and it was monitored by an automatic flow-injection electrochemical analysis system which was established on the basis of dynamic electrochemical technology with flow-through mini-type Na⁺ and Ca²⁺ electrodes.Simultaneous monitoring of the operational state of cation resin and the content of calcium citrate in effluent of the cation resin column was achieved by using this system.Through the investigation and optimization of the relevant factors,the total ionic strength adjustment buffer consisted of 80 mmol·L^-1 tris,175 mmol·L^-1 H₃BO₃,1 mmol·L^-1 KCl and 0.025 mmol·L^-1 CaCl₂,sample injection volume was 150 μl,total flow rate was selected at 2.26 ml·min^-1,length of mixing coil was 120 cm(I.D.0.5 mm).The linear determination ranges of the system were 2.0～1000 mmol·L^-1 for Na⁺,0.2～50 mmol·L^-1 for Ca²⁺,respectively,and the relative standard deviation was less than 0.68%(n=11).The detection limits were 1.12 mmol·L^-1 for Na⁺,0.093 mmol·L^-1 for Ca²⁺,respectively.

Key words: flow injection, cation resin, calcium citrate, flow-through electrode, sodium, calcium

摘要： 基于流动注射流通式Na/Ca微电极串联动态电化学自动检测系统,给出了一种阳树脂在线离子交换连续合成高纯度柠檬酸钙的新方法,并实现了对阳树脂柱的运行状态及流出液中柠檬酸钙含量的同时自动在线监测。通过对此系统的相关影响因素进行了考察和优选,得到的结果是:检测系统的总离子强度调节缓冲液由80 mmol·L^-1 tris、175 mmol·L^-1 H₃BO₃、1 mmol·L^-1 KCl和0.025 mmol·L^-1 CaCl₂的混合液(pH 8.0)构成,样品注入体积为150 μl,总流量为2.26 ml·min^-1,混合盘管长度为120 cm(I.D.0.5 mm);检测系统的测定范围分别为2.0～1000 mmol·L^-1 Na⁺,0.2～50 mmol·L^-1 Ca²⁺;相对标准偏差(RSD)小于 0.68%;其检测下限分别为1.12 mmol·L^-1 Na⁺,0.093 mmol·L^-1 Ca²⁺。

关键词: 流动注射, 阳离子交换树脂, 柠檬酸钙, 流通式电极, 钠, 钙