Gravimetric and spectrophotometric determination of some drugs--tertiary amine hydrochlorides in coated tablets

Four drugs in the form of coated tablets: Amitryptylinum (Amitryptyline) (1), Imipramin (Imipramine) (2), Chloropyribenzaminum (Chloropyramine) (3), and Phenazolinum (Antazoline) (4) were determined gravimetrically and spectrophotometrically in the same process by using complexes with ammonium molybdate. Stoichiometry of the complexes was established by elemental analysis and analysis of the incineration residue (MoO3). The complexes were characterized by IR and UV spectra and melting points. Contents of the drugs in the complexes were also determined spectrophotometrically. In this method Beer's law was found to obey over the concentration ranges 10-80 micrograms/ml (complex of 1), 10-100 micrograms/ml (complexes of 2 and 3), and 10-60 micrograms/ml (complex of 4). This method was validated in terms of precision, linearity, limit of detection and limit of quantitation. The two methods of the drug determination used in a single process of analysis, verify each other.