Spectroscopic studies on naftazone and its metal complexes with analytical applications for quality control of tablets

Abstract

The spectroscopic characteristics of the haemostatic drug naftazone (NFZ) as well as its metal complexing ability were investigated spectrophotometrically in order to develop new, simple and sensitive spectrophotometric methods for its determination. The first method was based on measurement of the absorbance of the drug in NaOH (2 × 10⁻³ M) at 494 nm. The method showed excellent linearity over the concentration range of 0.5–10.0 μg mL⁻¹. The second method was based on complex formation between NFZ and different metal ions including Cu²⁺, Ni²⁺, Co²⁺ and Zn²⁺ in borate buffer. The absorbances of the formed complexes were measured at 512, 506, 498 and 502 nm for Cu²⁺, Ni²⁺, Co²⁺ and Zn²⁺, respectively. Beer's law was obeyed within the concentration ranges of 2.0–14.0, 2.0–10.0, 2.0–14.0 and 2.0–19.0 μg mL⁻¹ for Cu²⁺, Ni²⁺, Co²⁺ and Zn²⁺complexes, respectively. The molar ratios and stability constants of the metal complexes were calculated and a proposal of the reaction pathway was consequently postulated. The proposed methods were validated according to ICH guidelines and they were successfully applied for the determination of NFZ in its tablet dosage forms without the interference from excipients normally added to tablets. The results of the proposed methods were favorably compared with those obtained by the comparison method using Student's t-test and variance ratio F-test.