Development and validation of an HPTLC-densitometry method for assay of glucosamine of different forms in dietary supplement tablets and capsules

A quantitative method using silica gel HPTLC plates, automated bandwise sample application, detection with ninhydrin chromogenic rea-gent solution, and automated visible mode densitometry has been developed for determination of glucosamine in nutritional supplements containing a variety of other active and inactive ingredients. Accuracy was validated by analysis of spiked blank and standard addition samples and precision by performing replicate analysis on a single day and different days. Recoveries of glucosamine hydrochloride from the spiked blank and standard addition samples were 100.0% and 101.5%, respectively. Repeatability for one sam-ple, which was analyzed six times on a single plate, was 1.72% relative standard deviation (RSD). The intermediate precision was 1.20% RSD for a sample analyzed in duplicate once per plate on five different days over a seven-day period. A survey was made of free glucosamine content compa-red to the label values for nine commercial supplement products using the new method, which is shown to be suitable for routine use in nutritional supplement analysis for manufacturing quality control or governmental regulatory purposes.