Determination of lignocaine and amprolium in pharmaceutical formulations using AAS

The ion-associate complexes of lignocaine hydrochloride (Lig.Cl) with ammon ium reineckate (Rk) or sodium cobaltithiocyanate, and that of amprolium hyd rochloride (Amp.Cl) with ammonium reineckate, have been prepared. The preci pitated ion-associates were subjected to elemental analyses, infrared and n uclear magnetic resonance spectroscopy and determination of the metal conte nt for elucidation of their structures. The solubilities of the solid ion-a ssociate complexes have been studied and their solubility products were det ermined at different temperatures at the optimum pH for their quantitative precipitation. The thermodynamic parameters DeltaH, DeltaG and DeltaS for t he dissolution of the ion-associate complexes were calculated. These ion-as sociate complexes have been used for the quantitative determination of the above mentioned drugs by precipitating them with an excess of the inorganic metal complex ions and determining the excess metal complex ions using ato mic absorption spectrometry. The method was applied for the determination o f the above drugs in pure solution and pharmaceutical preparations. 0.135-1 35.4 and 0.158-157.6 mg of lignocaine and amprolium, respectively, can be d etermined with mean relative standard deviations (R.S.D.) 0.92-1.20% and re covery values of 99.18 +/- 0.48 to 100.12 +/- 0.34% indicating high precisi on and accuracy. (C) 2002 Elsevier Science B.V. All rights reserved.