Indirect determination of cefradine with n-propyl alcohol–ammonium sulfate–water system by extraction–flotation of cuprous thiocyanate

A new method was developed for the determination of cefradine by extraction–flotation of CuSCN. The experiment indicated that in the presence of 0.20 mol/L NaOH the degradation of cefradine took place in water bath at 100 °C. The thiol group (–SH) of the degradation product could reduce Cu(II) to Cu(I) for the formation of the emulsion CuSCN in the presence of NH₄SCN at pH 4.0. By determining the residual amount of Cu(II) in the solution and calculating the flotation yield of Cu(II), the indirect determination of cefradine can be obtained. This method has been applied to determine cefradine in capsules, human serum and urine samples, respectively.