Determination of amitriptyline,imipramine and orphenadrine in antidepressant drugs by potentiometry,spectrophotometry and atomic absorption spectrometry

Methods are described for the determination of amitriptyline, imipramine and orphenadrine in some antidepressant drugs. They are based on a prior reaction with ammonium reineckate to form 11 water-insoluble drugreineckate ion-pair complexes. These complexes are (i) used as ion-exchangers in liquid-membrane electrodes responsive to the drug cations, (ii) extracted with nitrobenzene or dissolved in acetonitrile and spectrophotometrically measured at 525 nm and (iii) dissolved in 90% acetone followed by nebulization in an air-acetylene flame for atomic absorption spectrometric measurements of Cr at 358.6 nm. The reaction and monitoring conditions are optimized to permit determination of as little as 10 g/ml of the drugs. Determination of the drugs in some pharmaceutical preparations shows an average recovery of 98.8% of the nominal and a mean standard deviation of 0.8%. The results compare favorably with data obtained by the United States and British Pharmacopoeia methods.