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

The voltammetric behavior of Ni(II) complexes of three 4-quinolone antibacterials, namely: norfloxacin (NFX), ciprofloxacin (CFX) and sparfloxacin (SFX), was studied using direct current (DCt) differential pulse (DPP) and alternating current polarography (AC(t)). The different experimental parameters affecting the cathodic waves were carefully investigated, then a simple and sensitive method for the analysis of these compounds was developed. The proposed method depends upon the polarographic activity of Ni(II)-4-quinolone 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, CFX and SFX, respectively The waves were characterized as being irreversible, diffusion-controlled with limited adsorption properties. The current-concentration 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 for 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 formulations. 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 DPP, respectively The results obtained were favorably compared to those given by a reference method.