HPLC determination of glucosamine hydrochloride and chondroitin sulfate, weakly absorbing in the near UV region, in various buffer media

Some features of the HPLC determination of two hydrophilic substances that poorly absorb in the UV spectral region (chondroitin sodium sulfate and glucosamine hydrochloride), associated with the absorption in the near UV region (195 nm) of components of buffer solutions with different pH values (1.2, 4.5, and 6.8), are considered. Such solutions are used, for example, in comparative dissolution kinetics tests in pharmaceutical practice. At some pH, the subtraction of the areas of system peaks from the total areas of analyte peaks made it possible to compensate for the negative effect of the solvent. To determine glucosamine hydrochloride in 0.1 M HCl, a procedure was developed and validated, involving the synthesis of o-phthalic derivatives. The revealed analytical features are caused by that the solvent of the samples and the eluent do not match; the effect can be most pronounced in measurements in the near UV region and in the determination of ionic compounds.