Finally, a flow-rate of 3 mL/min, with a 2 s lapse
between both injections, was finally selected because of the best
sensitivity and precision of the signals were obtained at these
conditions. A 32 factorial design was used for the flow-rate
optimization of the other two channels. The flow-rates of imidazole
and hydrogen peroxide were studied in the range between
0.75 mL/min and 3.5 mL/min and using a flow-rate of 2 mL/min
as the center point. The function representing the relationship
among flow-rates of imidazole and hydrogen peroxide and the
chosen response is