Research on the Rapid Determination of Micro-fluorine in Garlic by the Method of Direct-reading Concentration after Standard Addition

[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.