The use of a factorial design for the response exploration of a flow inject
ion (FI) system is described and illustrated by Fl spectrophotometric deter
mination of paraquat. Variable response (absorbance) is explored as a funct
ion of the factors flow rate and length of the reaction coil. The present s
tudy was found to be useful to detect and estimate any interaction among th
e factors that may affect the optimal conditions for the maximal response i
n the optimization of the FI system, which is not possible with a univariat
e design. Ln addition, this study showed that factorial experiments enable
economy of experimentation and yield results of high precision due to the u
se of the whole data for calculating the effects.