超声消解FIA-FAAS快速测定环境水样中COD

Rapid determination of COD by FIA-FAAS based on ultrasound digestion

采用超声消解,流动注射-火焰原子吸收法对环境水样中COD进行了测定。采用酸性KMnO4作氧化剂,在80℃下超声消解,被COD还原生成的Mn^2＋经冷却后在线分离吸附于阳离子交换树脂微型柱上,用3 mol/L HCl反相洗脱,送至火焰原子吸收检测器检测。在消解时间30 s的条件下,测定COD的线性范围为3-300 mg/L,检出限为1 mg/L,采样频率为24 h^-1,Cl^-和Mg^2＋的质量浓度分别至1000 mg/L时均无干扰,对30 mg/L的标准样品重复测定9次,相对标准偏差为2.7%。该法用于河水、池塘水和自来水分析,获得了与经典重铬酸钾法基本一致的测定结果。

A rapid method of flow injection flame atomic absorption spectroscopy is proposed for the determination of chemical oxygen demand （COD） in environmental water samples based on tdtrasound digestion. By ultrasound digestion at 80℃ in a flow injection on-line preconcentration and separation system, the sample reacted with KMnO4 and the Mn（ Ⅱ ） produced was adsorbed on a mini-column filled with cation exchange resin. The adsorbed Mn（ Ⅱ ） was eluted reversely with 3 mol/L HCl to the nebulizer and measured by FAAS. When the length of the reaction coil was 5 m and adsorption time was 30 s, the calibration curve was linear over the range of 3 - 300 mg/L with an analytical frequency of 24 h^- 1. The detection limit of the method was 1 mg/L COD. Up to 10000 mg/L Cl^-1 and Mg^2 ＋ did not interfere with the determination. The method has been applied to the determination of COD in environmental water samples, and the results are in agreement with those obtained by traditional potassium dichromate method.