Separation and determination of sorbitol and xylitol in multi-component pharmaceutical formulations by capillary isotachophoresis

Abstract

Pharmaceutically important polyhydric alcohols sorbitol (SO) and xylitol (XY) are efficiently separated and determined by analytical capillary isotachophoresis (ITP) with conductometric detection. The on-column complex-formation equilibria between the polyols and boric acid are utilized—the terminating borate ion acts as the complexing agent. The ITP operational system used consists of 10 mM HCl+20 mM imidazole (LE, pH 7.0) and 20 mM boric acid (TE, pH 8. 0). The effective mobilities of the borated SO and XY are 8.3×10 −9 m 2 V −1 s −1 and 7.4×10 −9 m 2 V −1 s −1, respectively. The ITP analysis is performed with the driving and detection currents of 50 μA (for 700 s) and 20 μA, respectively. The calibration graphs are rectilinear in the range 25–250 mg l −1 of SO and 50 to 500 mg l −1 of XY. The method is applied to the simultaneous assay of SO and XY in three mass-produced multi-component infusion solutions. Favourable values of the method validation parameters obtained confirm the suitability of the proposed ITP method for the quality control of pharmaceuticals.