| The titanium and tungsten are important metal materials and widely used in medical industry, electronics, aviation, military and many other fields. The rapid development of modern technology needs more high-purity metals, the purity requirements are increasingly strict, too. The trace elements in high-purity metals play a key role in its property and application, as a result of which, the analysis of high-purity metals needs to be put forward to a higher level.With the hyphenated technique of laser ablation coupled with ICP-MS, solid sample could put into the LA cell derictly instead of dissolved by acid solution which makes the analytical process more convient and cleaner. It has been recognized as one of the best methods for testing trace element in high-purity metals.In this paper, LA-ICP-MS method was applied to determinate trace elements in high-purity titanium and tungsten. The working conditions were optimized. For the high-purity titanium, laser energy was 85%, pulse repetition rate was 20 Hz, ablation spot size was 150 μm, laser scan rate was 40 μm/s which was 60 μm/s for tungsten and He gas flow rate was 650 m L/min which was 700 mL/min for tungsten. We test the carrier gas when the sample were not ablated and recorded each elements’ signal intensity to calculate elements’ detetion limits of the method. Elements’ detetion limits of the method were between 10-7~10-9, which could meet the requirements of high-purity metals’ analyse. The mass fraction of trace elements in high-purity titanium was 0.10μg/g~13μg/g with the relative standard deviation between 8.2%~56%. The total content of impurity elements was 61μg/g and the purity of the high-purity titanium was 99.994%. The mass fraction of trace elements in high-purity tungsten sample was 0.071μg/g~12μg/g with the relative standard deviation between 6.9%~63%. The total content of impurity elements was 41μg/g and the purity of the high-purity tungsten was 99.996%.ICP-MS method was used to determine the content of trace elements in high-purity titanium and high-purity tungsten to verify the accuracy of LA-ICP-MS method. Each element’s best internal element was elect by recovery experiments. As the result, elements’ detetion limits of ICP-MS testing titanium were 0.016μg/g~2.3μg/g, determinations were in the range of 1.1μg/g ~16μg/g with the relative standard deviation between 6.5%~24%; Elements’ detetion limits of ICP-MS testing tungsten were 0.012μg/g~1.4μg/g, determinations were in the range of 0.64μg/g ~11μg/g with the relative standard deviation between 3.4%~15%. Except for element Ni, the recovery rate of trace elements in high-purity titanium and tungsten were all in the range of 91%~111%, which showed the favorable accuracy of LA-ICP-MS method.At the same time, GD-MS was used in this paper to test the high-purity titanium and tungsten samples. Before testing the sample, the working conditions were optimized by condition experiments. In this experiment, the discharge voltage was 660 V, discharge current was 45 mA and discharge gas was 440 mL/min. The mass fraction of trace elements in high-purity titanium was 0.048μg/g ~14μg/g and the relative standard deviation were 8.0%~58%. The mass fraction of trace elements in high-purity titanium was 0.011μg/g ~9.1μg/g and the relative standard deviation were 4.0%~65%.The t-test was used to compare the results of LA-ICP-MS with ICP-MS. Except for Ni and Au, the t value of trace elements in high-purity titanium and high-purity titanium samples were all less than the critical value of 2.23 under significance level of 0.05 which meant the result of LA-ICP-MS was reliable. The analysis capability such as detection limit and relative standard deviation between LA-ICP-MS, GD-MS and ICP-MS were compared and the result showed the detetion limits of LA-ICP-MS and GD-MS were lower than ICP-MS as well as the relative standard deviation were higher than ICP-MS. Finally, the paper expounded LA-ICP-MS method’s capability of low detetion limits, high sensitivity, celerity, real-time analyssi and microanalysis. |
