磷钒钼黄光度法测定钒磷铁矿中磷

采用无水碳酸钠和硼酸混合熔剂分解样品,在硝酸介质中,高锰酸钾将其他形式的磷酸根氧化为正磷酸根,以亚硝酸钠还原过量的高锰酸钾。在约0.80mol/L的酸度下,磷与钼酸铵、钒酸铵反应生成可溶性的磷钒钼黄络合物,实现了磷钒钼黄分光光度法对样品中磷的测定。在选定的实验条件下,显色液中磷的质量在0.023~0.278mg范围内符合比尔定律,校准曲线的相关系数为0.9998。方法检出限为0.20%(质量分数),测定下限为0.60%(质量分数)。考察了钒磷铁矿样品中钒、铬及其他共存元素对测定的干扰,结果表明这些共存元素的干扰均可忽略。选取6件钒磷铁矿样品,分别采用实验方法与国标方法GB/T 1871.1—1995(包括磷钼酸喹啉重量法和滴定法)作对照分析,二者测定结果基本一致。采用实验方法对钒磷铁矿样品进行8次平行测定,相对标准偏差(RSD,n=8)小于4%,在样品中加入磷标准溶液进行加标回收试验,回收率在98%~101%之间。

Determination of phosphorus in vanadium-phosphorus-iron ore by phosphorus vanadium molybdenum yellow spectrophotometry

The sample was decomposed with anhydrous sodium carbonate-boric acid mixed flux. The phosphates in other forms were oxidized to orthophosphates with potassium permanganate in nitric acid medium. Then, the excessive potassium permanganate was reduced by sodium nitrite. At the acidity of about 0.80mol/L, phosphorus could react with ammonium molybdate and ammonium vanadate to form soluble phosphorus-vanadium-molybdenum yellow complex, thus realizing the determination of phosphorus in sample by phosphorus vanadium molybdenum yellow spectrophotometry. Under the selected experimental conditions, Beer′s law was obeyed when the mass of phosphorus in coloring solution was in range of 0.023-0.278mg. The correlation coefficient of calibration curve was 0.9998. The detection limit of method was 0.20% (mass fraction), and the lower determination limit was 0.60% (mass fraction). The interference of vanadium, chromium and other coexisting elements in vanadium-phosphorus-iron ore with the determination was investigated. The results showed that the interference of these coexisting elements could be ignored. Six vanadium-phosphorus-iron ore samples were selected and determined by proposed method and national standard method (GB/T 1871.1-1995, including quinoline phosphomolybdate gravimetric method and titration method) for comparison analysis. It was found that the determination results were basically consistent. The vanadium-phosphorus-iron ore was determined for eight parallel times according to the proposed method. The relative standard deviation (RSD, n=8) was less than 4%. The standard solution of phosphorus was added into sample for recovery test, and the recoveries were between 98% and 101%.