EQUILIBRIUM STUDIES OF COMPLEXES WITH METAL IONS AND POTENTIOMETRIC AND CONDUCTOMETRIC DETERMINATION OF NALIDIXIC ACID IN TABLETS

Ten metal ions viz, Fe(III), Cr(III), La(II), Sn(II), Co(II), Ba(II), Pd(II), Ti(II), Sr(II) and Zr(II), were selected to elucidate the interaction of these metal ions with nalidixic acid(NAL) using potentiometric and conductometric methods. The ionization constant of the ligand and stability constants of the complexes formed have been tabulated at 25±1.0Cº and 0.01 M ionic strength of NaCl in 25 %( v/v) aqueousethanol solution. Complexes of 1:1, 1:2 and/or 1:3 metals to ligand ratios are formed depending on the nature of the ligand or metal ions. As well as, the stoichiometry of complexes confirmed by conductometric method. Also simple, precise, rapid and low-cost potentiometric and conductometric methods for nalidixic acid determination in pure form and tablets are proposed. Nalidixic acid present in tablets containing known quantity of drug were potentiometrically titrated by 0.1M of NaOH using a combined glass pH electrode. The detection limit was 2.20 mg /25ml. The calibration graph is linear in the range of 0.23– 2.55 mg/25ml. The correlation coefficient of determination (r) comes out to be 0.9972. The standard deviation (SD) was 2.77. No interferences were observed in the presence of common components of the tablets. The percentage recoveries of nalidixic acid in tablet dosage formulations by potentiometric and conductometric methods were (95.8-98.68) %, with standard deviations (SD) were within (0.18–0.4) (n=5).