提出将流动注射电化学分析系统(离子选择电极电位检测)应用于离子交换法制备柠檬酸钠生产流程中对离子交换树脂的运行状态和从交换柱流出液中柠檬酸钙含量的自动在线监测。经试验并优化的检测条件如下:① 总离子强度调节缓冲溶液(TISAB)每升中含80 mmol Tris,175 mmol硼酸、1.0 mmol氯化钾和0.025 mmol氯化钙,此混合溶液酸度为pH 8.0;② 样品注入体积为150 μL;③ 总流量为2.26 mL·min-1;④ 混合盘管长度为120 cm(内径0.5 mm)。测定钠离子的线性范围为2.0~1 000 mmol·L-1,测定钙离子的线性范围为0.2~50.0 mmol·L-1;钠离子选择电极和钙离子选择电极的测定下限依次为1.12,0.09 mmol·L-1。分别对上述二离子的低浓度和高浓度混合标准溶液连续测定11次,测定值的相对标准偏差均小于0.7%。

A flow-injection electrochemoanalytical system was proposed and applied to in-situ supervising analysis for content of the product and state of production in the process of preparation of calcium citrate by cation exchange. As shown by the experimental results, the optimized testing conditions were given as follows: ① a mixed solution containing 80 mmol of Tris, 175 mmol of boric acid, 1.0 mmol of KCl and 0.025 mmol of CaCl2 in 1 L of solution was used as TISAB (pH 8.0) in the analysis; ② 150 μL was taken as the volume of sample injection; ③ total flow-rate taken was 2.26 mL·min-1; and ④ length of the mixing coil taken was 120 cm (with i.d. 0.5 mm). Linearity ranges found for determination of Na+ ion and Ca2+ ion were between 2.0-1 000 mmol·L-1 and 0.2-50.0 mmol·L-1 respectively. Values of lower limits of determination found for the ISE of Na+ and Ca2+ were 1.12 mmol·L-1 and 0.09 mmol·L-1 respectively. Tests for precision were made with mixtures of standard solutions of Na+ and Ca2+ at low and high concentrations, values of RSD′s (n=11) found were all less than 0.7%.