Determination of verapamil in pharmaceutical formulations using atomic emission spectrometry.

Ion-associate complexes of verapamil hydrochloride (VpCl) with (Cd(II), Co(II), Mn(II), and Zn(II)) thiocyanates, potassium ferricyanide, and ammonium reineckate are precipitated. The solubility of the solid complexes at the recommended optimum conditions of pH and ionic strength values have been studied. Saturated solutions of each ion associate at different temperatures under the optimum precipitation conditions were prepared and the metal ion contents in the supernatant were determined. The solubility products were thus calculated at different temperatures and the thermodynamic parameters DeltaH, DeltaG, and DeltaS were calculated. A new accurate and precise method based on direct coupled plasma atomic emission spectrometry for the determination of VpCl (1.96-62.86 microg ml(-1)) in pure solutions and pharmaceutical preparations is given.