比浊法测定硼酸中的氯和硫酸根

Measurement of Cl-and SO_4^(2-) in boric acid by turbidimetry

主要研究在酸性介质中采用光电比浊法测定硼酸中微量氯和硫酸根。分别讨论了稳定剂的选择、酸度、沉淀剂用量、加热温度和时间以及测量时间对溶液浊度的影响,从而确定了测试的最优条件,使分析易于操作。硫酸根的测定中选用丙三醇-乙醇(体积比为1∶4)混合溶液作稳定剂,沉淀剂为酸性氯化钡溶液,采用手动振荡使待测液均匀,并对待测液加热,使试剂的加入顺序对结果无影响,方法的检出限为0.10 mg/L,相对标准偏差RSD<0.03%,回收率在98.85%~103.00%,测量时间保持在40 min以上。硫酸根质量浓度在0.33~0.83 mg/L与浊度值之间呈良好的线性关系。氯的测定中,加入丙三醇作稳定剂,可使测量时间保持在40 min,检出限为0.03 mg/L,RSD<0.04%,回收率在102.2%~106.5%,氯质量浓度在0.10~0.25 mg/L与浊度值之间呈良好的线性关系。光电比浊法提高了测定的精密度与准确度,方法简便、可靠、无毒,可在实际中应用。

Microcontents of Cl^- and SO4^2- in boric acid were determined by photoelectricity turbidimetry with acid as medium. The effects of stabilizer selection, acidity of solution, dosage of precipitant, heating time and temperature as well as measuring time on the turbidity of solution were studied. The optimum experiment parameters were confirmed, which simplified the operation process. In the measurements to determine SO4^2- in boric acid, stabilizer was glycerine - ethanol （ 1 ： 4 by volume ratio）, precipitant was acidic BaCl2 solution. The solution was shaken manually to mix well and heated, as a result, the adding sequence of reagents had no effects on results. The detection limit was 0. 10 mg/L, relative standard deviation （ RSD ） was less than 0.03% , recovery rate was 98.85% - 103.00%, and measuring time lasted over 40 min. SO4^2- concentration in the range of 0.33 - 0.83 mg/L showed a linear relationship with turbidity. In the measurements of chlorine, the stabilizer was glycerine,measuring time held in 40 min,detection limit was 0.03 mg/L,RSD was less than 0.04% ,and recovery rate was 102.2% - 106.5%. Cl^- concentration in the range of 0.10 - 0.25 mg/L showed a linear relationship with turbidity. Photoelectricity turbidimetry improved the precision and accuracy of the measurements. The method of turbidimetry to determine Cl- and SO4^2- in boric acid is simple, reliable,innocuous, and applicable in practice.