Continuous flow molecular emission cavity analysis of cephalosporins by alkaline degradation to sulphide

Abstract

A continuous flow method for the determination of some cephalosporins (cephradine, cephalexin, cephalosporin C, cefadroxil, cephapirin and cephalothin) in the general range 10.0–250.0 µg ml^–1 is described. The sample is mixed with sodium hydroxide and remains for 20 min at 90 °C in the delay coil of an air-segmented system. The solution is then mixed with an excess of orthophosphoric acid, and the hydrogen sulphide evolved is continuously transferred into the cavity for generation of the S₂ molecular emission. The analysis is automated, requires no sample pre-treatment and samples can be analysed at a rate of 30 per hour with a relative error of 1–2%. The method was evaluated by carrying out recovery experiments and by the analysis of commercial formulations. Results agreed well with those obtained by the standard methods.