Analytical investigation of beta-lactam antibiotics in pharmaceutical preparations. IX. Colorimetric determination of six cephalosporins of second and third generation in the range of micromolar concentrations.

A sensitive, accurate, precise and the same time simple and rapid method for the colorimetric determination of some cephalosporins of the second and third generations, such as: cefoxitin sodium (CFXT), cefaclor (CFCL), cefamandole nafate (CFMD), ceforanide l-lysine (CFRN), cefotaxime sodium (CFTX), and cefurozime sodium (CFRX) was described. The new method proposed is based: a) On the reduction of Fe(III) to Fe(II) by the drug analysed and b) On complexation of Fe(II) formed with o-Phenanthroline (O-Phen) consistently the formation of the well known highly stable orange-red coloured chelate complex [Fe(II)-(o-Phen)3]2+ which exhibits an absorption maximum at lambda = 510 nm (pH 4.50 +/- 0.2). Beer's law is obeyed for: 1.0 - 37.5 microgram mL-1 for CFX, 1.0 - 25.0 microgram mL-1 for CFMD, CFRN, and CFTX and 2.0 - 37.5 microgram mL-1 for CFTX and CFCL, while the apparent molar absorptivity ( epsilon in L mol-1cm-1) and the Sandell's sensitivity in (ngcm-2) both referred to the drug analyzed, are 1.29 x 10(4); 34.7 (CFXT), 7.61 x 10(3); 50.7 (CFCL), 3.33 x 10(4); 15.4 (CFMD), 2.60 x 10(4); 17.6 (CFRN) respectively. The regression line equation for each one of the above studied cephalosporins were calculated with a correlation coefficient 0.9997 < r < 1.0000; the accuracy and the precision of the method was considered as very satisfactory, while the results of a statistical analysis by means of the Student's t-test and the variance ratio F-test prove that no significant difference was observed between the results of the proposed method and those of official one.