Potentiometric and spectrofluorimetric studies on complexation of tenoxicam with some metal ions.

The interaction of tenoxicam with six metal ions, viz. Fe(III), Bi(III), Sb(III), Cr(III), Cd(II) and Al(III) was studied using potentiometric and fluorimetric methods. In the potentiometric method the ionization constant of the ligand and stability constants of the complexes formed have been tabulated at 25+/-0.1 degrees C, ionic strength of NaNO3 in 50% (v/v) aqueous acetonitrile solution was 0.05 mol x dm(-3). Complexes of 1:1 and/or 1:2 and/or 1:3 metal to ligand ratios are formed. The fluorescence of tenoxicam in the presence and absence of the metal ions was studied. The drug can be determined fluorimetrically in 0.5 M HNO3 at an emission wavelength of 450 nm (excitation at 350 nm). The linear range is 0.040-0.2 microg/ml in the absence of Al(III) and 0.016-0.1 microg/ml in the presence of Al(III). Tenoxicam was determined by the proposed method in tablet, suppository and injection. The recovery percent ranged from 98.16 to 102.22%. The effect of 2-aminopyridine on the recovery of tenoxicam was also investigated.