Inefficient mixing of reagents with elctrophoretically mediated microanalysis (EMMA) and the degradation of the reaction product (Janovosky complex) have been previously identified as limitations associated with CE-based in-line assays for creatine. Calculations that assume constant voltage field do not accurately predict the optimal mixing parameters. Through digital simulation (freeware program Simul-5) of experimental conditions (3 mm sample zones of 20 mM creatinine and 47 mM alkaline sodium picrate, various borate BGEs at pH 9.0) local electric field intensities in the reagent zones were found to vary widely from 260 kV/m to 0.83 kV/m, indicating the consideration of non-homogeneous fields is more important than was previously realized. Correlation of experimental and calculational data will be shown. In addition, counter ions have been found to pay an important role in achieving optimal conditions for both reactant overlap and product stacking. Secondly, the degradation of the in-line generated product was investigated. By periodic reversal of the potential, the product was electrophoresed back and forth across the detector window within an 8 cm segment of the capillary centered around the detection point. The decay of the Janovosky product peak area illustrated first order degradation kinetics (0.085 S-1 to.153 S-1 ). The rate of degradation increased with both elevated borate buffer concentration and pH, but was considerably slower (< 10-4 S-1) when no potential field was applied. By combining conditions for both optimal overlap and minimum product degradation an optimized CE based method can be developed.