Determination of cobalt, nickel, iron, niobium, tantalum, vanadium and chrome in tungsten-based hard alloy by microwave digestion-inductively coupled plasma atomic emission spectrometry
Abstract： The tungsten-based hard alloy samples (such as tungsten-cobalt and tungsten-nickel) were digested by high pressure closed microwave heating method using nitric acid-phosphoric acid (V(HNO3):V(H3PO4)=5:1) as digestion reagent. After dilution with water, the content of Co, Ni (0.005%-10%), Fe, Nb, Ta, V, Cr and Mo (0.005%-1%) in digestion solution was directly determined by microwave digestion-inductively coupled plasma atomic emission spectrometry (ICP-AES). The effect of nitric acid and phosphoric acid concentration on sample digestion was investigated. The optimal digestion conditions such as microwave control parameters were studied. The sample digestion method by microwave digestion was established. The matrix tungsten was complexed with inorganic reagents, avoiding the loss of some elements due to the precipitation of tungstic acid and the spectral interference due to the use of organic complex reagents. The results showed that the following digestion procedure was good: the temperature was increased to 130 ℃ within 5 min and kept for 5 min; then, it was increased to 190 ℃ within 5 min and kept for 15 min. The effect of high content matrix tungsten and spectral interference were eliminated by selecting analytical lines, matrix matching and synchronous background correction. The reliability of method could be guaranteed. The background equivalent concentration was from 5 μg/L (Nb) to 18 μg/L (Fe), and the detection limit was from 4 μg/L (Nb) to 13 μg/L (Fe). The proposed method was applied to the determination of alloy or impurity elements in tungsten-based hard alloy samples. The relative standard deviation (RSD) was less than 3%, and the recovery rate of standard addition was 97%-104%. The determination results were consistent with those obtained by national standard method.
［8］ 黄冬根,廖世军,党志. 钨精矿中杂质元素ICP-MS测定方法的研究［J］. 稀有金属材料与工程（Rare Metal Materials and Engineering）, 2006,35(2):333-336.
［9］ Ma X G, Li Y B. Determination of trace impurities in high-purity zirconium dioxide by inductively coupled plasma atomic emission spectrometry using microwave-assisted digestion and wavelet transform-based correction procedure［J］. Anal. Chim. Acta, 2006, 579(1): 47-52.
