长光路萃取光度法测定痕量氟

Extraction/Spectrophotometric Determination of Fluoride at Trace Level by Long Capillary Cell

以新型氟树脂长光纤作吸收池，用二甲苯胺的异戊醇作萃取剂，氟、硝酸镧与茜素络合剂形成三元络合物。为保持有机相的清澈，加入 0．10 mL无水乙醇代替HAc-NaAc缓冲溶液洗涤有机相，并以乙醇稀释有机相后测定。用110cm长的毛细管在 580 nm处测定吸收，氟的线性范围在 0～32 μg/L服从比尔定律。该法具有高灵敏度，高稳定性等优点，适用于测定天然水中氟，对含氟1.10 mg／L～0．13 mg/L的水样，其回收率在 99％～101％；相对标准偏差小于6％。

A new extraction/spectrophotometric determination of trace amounts of fluoride with a long capillary cell has been developed. The alizarin complexone and lanthanum nitrate can form with fluoride a blue colored ternary complex which may be extracted with N,N- diemethylaniline in isoamyl alcohol. In order to keep the.organic phase clear, 0.1 mL of an- hydrous ethanol is added into it instead of washing with HAc-NaAc buffer solution and ap- propriate amount of ethanol is used to dilute the organic phase. The absorbance is measured at 580 nm with a 110cm capillary cell. Beer's law is obeyed over the range 0~32 μg/L of fluoride. The method has some advantages, such as high sensitivity and stability. Water samples containing 0.10-0.12 mg/L fluoride are determined with a recovery of 99%- 101% and a relative standard deviation less than 6%.