Dissolve a quantity of the sample in water to obtain a solution containing 10 mg/ml, heating in a water bath at 60º, if necessary. Similarly, prepare a standard solution of potassium gluconate in water containing 10 mg/ml.
Apply separate 5-µl portions of the test solution and the standard solution on a suitable thin-layer chromatographic plate coated with 0.25-mm layer of chromatographic silica gel, and allow to dry. Develop the chromatogram in a solvent system consisting of a mixture of ethanol, water, ammonium hydroxide, and ethyl acetate (50:30:10:10) unti1 the solvent front has moved about three-fourths of the length of the plate. Remove the plate from the chamber, and dry at 110º for 20 min. Allow to cool, and spray with a reagent, prepared as follows: Dissolve 2.5 g of ammonium molybdate in about 50 ml of 2 N sulfuric acid in a 100-MI volumetric flask, add 1.0 g of ceric sulfate, swirl to dissolve, dilute with 2 N sulfuric acid to volume, and mix. Heat the plate at 100º for about 10min. The principal spot obtained from the test solution corresponds in colour, size, and retention to that obtained from the standard solution.
Note: This test will be included in General Methods (Guide to JECFA Specifications), FNP 5/Rev 3.
