Fluorescence densitometric method for the determination of gluconic and lactobionic acids ("sugar acids") in pharmaceutical preparations.

An in situ fluorimetric method has been developed for the quantitation of gluconic and lactobionic acids and their salts in tablet formulations. The method is based on glycol cleavage with lead tetraacetate followed by treatment with dichlorofluorescein. Calcium gluconate and lactobionate were determined in Calcium-Sandoz and Ca-C 1000 Sandoz effervescent tablets. The reproducibility corresponded to relative standard deviations between 0.7 and 3.5% (usually below 2%). Detection limits of 0.2 mug per spot can be obtained. Interfering compounds such as citric acid, sugars and ascorbic acid can be separated from the "sugar acids". The linearity of the calibration graphs between 0.5 and 5 mug per spot is satisfactory (r = 0.994-0.999). The method is simple and could be applied to the routine analysis of suitable pharmaceutical formulations. Other compounds with glycol structures should also be adaptable to this technique.