对磺基苯偶氮变色酸分光光度法测定岩石样品中的氟

采用对磺基苯偶氮变色酸分光光度法对岩石样品中氟的含量进行测定。确定的最佳测定条件为:测定波长570 nm,放置2 h后测定,盐酸介质浓度0.84 mol/L,显色剂用量5.0 mL。氟离子浓度在0~1.4 mg/L时符合比尔定律,方法检出限为0.06μg/g。以岩石标准物质代替氟标准溶液制作标准曲线,可有效降低杂质元素的干扰。对国家一级标准物质和日本玄武岩标准物质6次测定的相对标准偏差(RSD)为2.37%~6.32%。

Spectrophotometric Determination of Fluorine in Rock Samples with p-Sulfophenylazo Chromotropic Acid

The concentration of fluorine in rock samples was determined by spectrophotometry in p-sulfophenylazo chromotropic acid (SPADNS) system. The best determination conditions are: measurement wavelength of 570 nm, determination media of 0.84 mol/L HCl, chromogenic reagent (SPADNS) dosage of 5.0 mL and reaction equilibrium time of 2 h. The Beer's law was obeyed in 0～1.4 mg/L of F~- with detection limit of 0.06 μg/g. The interference from coexistent elements could be effectively reduced by using standard rock samples for calibration instead of using standard fluorine solutions. The method has been applied to the determination of fluorine in National Standard Reference Materials and Japan Standard Reference Basalt sample. The results are in agreement with certified values with precision of 2.37%～6.32% RSD (n=6).