利用孔雀绿-磷钼杂多酸分光光度法测定水样中微量磷酸盐

摘要

[目的]磷钼蓝分光光度法是水中磷酸盐含量的常用检测方法,但不适用于磷酸盐含量低(＜0.04mg/L)的水样.建立一种更准确的水中微量磷酸盐检测方法.[方法]对孔雀绿-磷钼杂多酸分光光度法中最大吸收波长、显色剂中孔雀绿和浓硫酸的比例与用量、表面活性剂聚乙烯醇(PVA)用量、显色稳定时间等指标依次优化,选择1个湖水样品和系列低浓度磷标准溶液,用优化后的测定方法进行方法回收率、精密度和检出限研究.[结果]优化后的关键点是最大吸收波长620 nm,显色剂配制比例钼酸铵溶液(176.5 g/L)/孔雀绿溶液(11.2 g/L)/浓硫酸=40/32/34(体积比),显色体积中显色剂比例占8％,显色稳定时间30 min,方法检出限为1.2 g/L,磷(P)浓度小于10.00μg/L时相对标准偏差RSD 8.3％ ～9.1％,P浓度大于10.00μg/L时RSD小于5％,加标回收率在97.0％～108.2％.[结论]优化后的孔雀绿-磷钼杂多酸分光光度法检测限低,灵敏度高,线性范围宽,显色溶液稳定,准确度、精密度符合水质测定需求,操作简便,适合环境中水体微量磷酸盐含量的检测.%[Objective] Phosphorus molybdenum blue spectrophotometry is a commonly used method for the determination of phosphate in water,but it is not suitable for Iow concentration (＜0.04 mg / L).This paper attempts to establish a more accurate method for the determination of trace phosphate in water.[Method] The maximum absorption wave length,the ratio and amount of malachite green and concentrated sulfuric acid in the colorant,the amount of PVA,the color stability time and so on were optimized in the range of the maximum absorption wave length of the malachite green-phosphomolybdate heteropoly acid spectrophotometry.The recovery rate,precision and detection limit of the optimized method were studied using a lake sample and a series of low concentrations of phosphorus standard solution.[Results] The maximum absorption wavelength was 620 nm,the volume ratio of ammonium molybdate (176.5 g/L)/sulfuric acid(11.2 g/L)/malachite green was 40/32/34 in chromogenic agent.The proportion of color reagent in color development accounted for 8％,PVA 4％.Color stability time was up to 12 h.The detection limit was 1.2 μg/L,the relative standard deviation RSD was in the range of 8.3％-9.1％ when the phosphorus concentration was less than 10.00 μg / L,and the RSD was less than 5％ when the P concentration was more than 10.00 μg/L.The recovery rate was in the range of 97.0％-108.2％.[Conclusion] The modified malachite green-phosphomolybdate heteropoly acid spectrophotometric detection limit is low,the sensitivity is high,the linear range is wide,the color solution is stable,the accuracy and precision meet the water quality requirement,and the operation is simple and suitable for the microphosphate content of the detection.