β-环糊精存在下,在pH 1.6的KCl-HCl缓冲溶液中,F~-与FeCl_3反应生成白色结晶性络盐使溶液褪色,据此建立了褪色光度法测定氟的新方法.络合物的最大褪色波长为263nm,体系的褪色程度与F~-浓度在0～10.0 mg/L范围内呈线性关系,检出限为47.9μg/L.大量金属离子的干扰采用蒸馏法分离或8-羟基喹啉沉淀法去除;MnO_4~-、Cr_2O_7~(2-)和VO_3~-的干扰用抗坏血酸掩蔽.方法用于测定磷矿和药厂工序废水中氟时,PO_4~(3-)和Ca~(2+)的干扰用蒸馏法分离去除,相对标准偏差小于2.3%(n=5),平均回收率为98%～102%.
A new fading spectrophotometric method was developed for the determination of fluorine. The method is based on the reaction between F~- and FeCl_3 in KCI-HCI buffer solution at pH 1-6 in the presence of β-cyclodextrin, which forms white crystalline complex salt, resulting in fading of the solution. The maximum fading wavelength lo-cated at 263 nm. The system's fading degree was linear with the concentration of F~- in the range of 0-10. 0 mg/L. The detection limit was 47. 9 μg/L. Many metal ions could be separated by distillation or precipitation with 8-hydroxyquinoline. Interfering ions of MnO_4, Cr_2 O_7~(2-) and VO_3 could be masked by ascorbic add. The method was applied to determine fluorine in phosphorus ore sample and wastewater sample of working procedure from pharma-ceutical factory, and the interfering ions of PO_4~(3-) and Ca~(2+) were separated by distillation. The relative standard devi-ation was no larger than 2. 3 % (n = 5), and the average recovery was in the range of 98 %-102 %.
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