Polarographic determination of some 4-quinolone antibacterials via their Ni(II)-complexes

The voltammetric behavior of Ni(II) complexes of three 4-quinolone antibact erials, namely: norfloxacin (NFX), ciprofloxacin (CFX) and sparfloxacin (SF X), was studied using direct current (DCt) differential pulse (DPP) and alt ernating current polarography (AC(t)). The different experimental parameter s affecting the cathodic waves were carefully investigated, then a simple a nd sensitive method for the analysis of these compounds was developed. The proposed method depends upon the polarographic activity of Ni(II)-4-quinolo ne complexes in Brinon-Robinson buffers (BRb) over the pH range (4.0-8.0). A well-defined, cathodic wave was created at pH 6.0, 5.5 and 6.5 for NFX, C FX and SFX, respectively The waves were characterized as being irreversible , diffusion-controlled with limited adsorption properties. The current-conc entration relationship was found to be linear over the range 2.0-6.4 x 10(- 5) M, 0.8-3.2 x 10(-5) M, for NFX, 2.0-6.4 x 10(-5) M, 0.8-5.6 x 10(-5) M f or CFX and 2.0-7.2 x 10(-5) M, 0.8-4.8 x 10(-5) M for SFX using DCt and DPP modes, respectively. with minimum detectability (S/N = 2) of about 2 x 10( -7) M for all the studied compounds. The method described was successfully applied to the determination of NFX, CFX and SFX in bulk and tablet formula tions. The average % recoveries for the studied compounds were 99.58 +/- 0. 72 to 100.50 +/- 0.79 and 99.50 +/- 0.71 to 100.17 +/- 0.29 using DCt and D PP, respectively The results obtained were favorably compared to those give n by a reference method.