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

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