| Abstract: | Abstract The cephalosporins studied, cefotaxime, cefazolin and cefoxitin react with alkaline picrate showing a complex kinetic behaviour which include a decomposition step in the case of cefotaxime and cefazolin. Cefoxitin does not conform strictly to pseudo-first order kinetics which seems to indicate that one or more intermediate reaction products might be formed before the final complex, or this might be unstable. The presence of the cephalosporins leads to results affected by systematic errors in the determination of creatinine in serum. This effect can be minimized for cefotaxime and cefazolin by choosing a specific time interval to process the analytical signal, δA. These intervals are 180–45 and 60–10s, respectively. The presence of cefoxitin requires the application of the generalized standard-addition method, which involves the simultaneus determination of creatinine and cefoxitin by measuring the δA for two different time intervals. |
