A simple method for the spectrophotometric determination of cephalosporins in pharmaceuticals using variamine blue

A simple spectrophotometric method for the determination of cefotaxime, ceftriaxone, cefadroxil and cephalexin with variamine blue is presented. The determination is based on the hydrol- ysis of β-lactam ring of cephalosporins with sodium hydroxide which subsequently reacts with iodate to liberate iodine in acidic medium. The liberated iodine oxidizes variamine blue to violet colored species of maximum absorption at 556 nm. The absorbance is measured within the pH range of 4.0- 4.2. Beer's law is obeyed in the range of 0.5-5.8 ∝g mL-1, 0.2-7.0 ∝g mL-1, 0.2-5.0 ∝g mL-1 and 0.5- 8.5 ∝g mL-1 for cefotaxime, ceftriaxone, cefadroxil and cephalexin respectively. The analytical param- eters were optimized and the method is successfully applied for the determination of cefotaxime, cef- triaxone, cefadroxil and cephalexin in pharmaceuticals.