[目的]建立一种快速测定食品中微量氟的新方法.[方法]用超声波浸提法提取大蒜中的氟离子,利用离子选择性电极在加入标准溶液后直接读取样品液的氟浓度.[结果]大蒜的水分含量平均值为77.730%,其RSD为2.1%.各因素对样品液氟含量的影响依次为:超声温度＞料液比＞超声时间,大蒜氟离子的最佳提取工艺:料液比为0.5:25.0,在25 ℃下超声提取3 min.氟电极的斜率转换系数为97.9%.试验测得样品液氟含量的平均值为29.076 μg/g,其RSD为2.6%.在测定样品液氟含量条件下,10.00 μmol/L氟标准液氟含量的平均测定值为9.875 μmol/L,相对误差为-1.25%.[结论]利用离子选择性电极,结合加标浓度直读法与超声波浸提技术快速测定大蒜中微量氟的方法简便、直观,适用于现场快速测定.%[Objective] The aim was to set up a new method for determining the micro-fluorine in food rapidly. [Method] The fluorine ions were extracted from garlic by ultrasonic extraction, by using ion selective electrode, the fluorine concn. of sample solutions were read directly after adding standard solution. [Result] The average value of water content in garlic was 77.730% and its RSD was 2.1%. The influences of various factors on the fluorine contents in sample solutions were as follows: ultrasonic temperature > ratio of material to liquid > ultrasonic time and the optimum extraction technology of fluorine ions from garlic was ultrasonic extraction with ratio of material to liquid of 0.5:25.0 at 25 ℃ for 3 min. The slope conversion coefficient of fluorine electrode was 97.9%. The average value of determined fluorine contents in sample solutions in this experiment was 29.076 μg/g and their RSD was 2.6%. Under the conditions for determining the fluorine contents in sample solutions, the average determination value of fluorine content in standard 10.00 μmol/L fluorine solution was 9.875 μmol/L and its relative error was-1.25%. [Conclusion] By using ion selective electrode, the method of determining the micro-fluorine in garlic rapidly by combining direct-reading concentration after standard addition with ultrasonic extraction technology was simple, convenient and visualized and it was suitable for fast-field evaluation.
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