SEPARATION AND DETERMINATION OF PHARMACEUTICALLY IMPORTANT POLYOLS INDOSAGE FORMS BY CAPILLARY ISOTACHOPHORESIS

Capillary isotachophoresis (ITP) with conductometric detection has bee n used for separating polyols such as mannitol, sorbitol, dulcitol and xylitol. Since the polyols behave as extremely weak acids in aqueous medium, the complex-formation equilibria between boric acid and the an alytes was employed to convert the neutral analytes into ionic species . The characteristic feature of this approach is the use berate, which functioned both as the complexing agent and the terminating ion. The ITP electrolyte system, optimised with respect to the sensitivity of t he ITP determination and the quality of separation, consisted of 10 mM HCl+20 mM imidazole (pH 7.1) containing 0.05% poly(vinylalcohol) as t he leading electrolyte and 20 mM boric acid (pH 8.1) as the terminatin g electrolyte. The driving and detection currents were 50 mu A (for 63 0 s) and 20 mu A, respectively. The effective mobilities of the borate -polyol complexes were determined; efficient separation of mannitol-so rbitol, sorbitol-xylitol and sorbitol-dulcitol mixtures was achieved. The calibration graphs were rectilinear (r=0.9995-0.9999) in the range s 10-200 mg l(-1) of sorbitol or mannitol. The relative standard devia tions were 1.4 to 1.8% (n=6) when determining 100 or 200 g l(-1) of ma nnitol and/or 50 to 200 g l(-1) of sorbitol in mass-produced infusion solutions. A single analysis took about 20 min. The results obtained b y the ITP method were in good agreement with those of the standard pha rmacopoeial iodimetric method.