双波长标准加入法同时测定合金钢中钼和钨

Simultaneous Determination of Molybdenum and Tungsten in Alloy by Dual wavelength Standard Addition Spectrophotometry

在金属离子显色体系中，采用双波长分光光度法同时测定了合金钢中的钼和钨。对显色反应和光度测定的最佳条件进行了详细考察。在介质盐酸浓度为０．６～１．２ ｍ ｏｌ／Ｌ，ＳＡＦ质量浓度为２０～６０ ｍ ｇ／Ｌ，ＣＴＭＡＢ质量浓度为０．１８～０．４２ ｇ／Ｌ的显色休系中，能够形成Ｗ－ＳＡＦ－ＣＴＭＡＢ和Ｍｏ－ＳＡＦ－ＣＴＭＡＢ络合物，吸光度值高且稳定。根据两络合物的吸收光谱，选择钼作为标准加入组分，在钨的等吸收点波长５０８ ｎｍ和５２０ ｎｍ 处对试样进行标准加入测定，由两波长下的回归直线交点坐标（ｃＯ，Ａ０） 及钨的回归方程计算出样品中钼、钨的含量。钼的质量浓度在０～１２ μｇ／２５ｍ Ｌ，钨在０～２５ μｇ／２５ｍ Ｌ范围内遵从比耳定律。对四个合金钢标样测定的相对标准偏差（ｎ＝ ６）＜ ３％ ，相对误差＜ ±５％ 。

Dual wavelength standard addition spectrophotometry has been applied to simultaneous determination of molybdenum and tungsten in alloy by using the system of metal ions SAF CTMAB.The optimum conditions for complexation and spectrometric determination were investigated in detail.The high and stable absorption of the complex Mo SAF CTMAB and W SAF CTMAB could be obtained in 0 6～1 2 mol/L HCl,20～60 mg/L SAF and 0 18～0 42 g/L CTMAB.The maximum absprption is at 523 nm and 514 nm for molydenum and tungsten, respectively.According to the visible absorption spectra of the two complexes,hexavalent molybdenum was used as standard addition component and the wavelengths at iso absorption pionts of W(Ⅵ) SAF CTMAB,508 nm and 520 nm,were accurately selected as the measuring wavelengths.Then the contents of molybdenum and tungsten were figured out from the intersecting point of the two regression lines.Beer's law is obeyed for 0～12 μg/25mL of molybdenum and 0 ～25 μg/25 mL of tungsten.The method is simple,rapid and effective in simultaneous determination of molybdenum and tungsten in alloys.The RSD(6 replicates) of four alloy references was less than 3%,and the relative errors were less than ±5%.All the results indicate that the present method is satisfactory.