A flow system with in-line blank correction applied to the spectrophotometric determination of total iron and chromium (VI) in wastewaters.

A flow system using the sample as the carrier with a propulsion device located after the detector is presented. This approach allows the correction of the intrinsic color of the sample, as it provides baseline adjustment for each sample. A confluence situated just after the selection valve allows the sample composition to be adjusted for the colorimetric measurement. The developed methodology was applied to the colorimetric determination of total Fe and Cr (VI) in wastewaters at 0.1-6.0 mg L-1 and 0.03-1.0 mg L-1, respectively. RSDs lower than 3% and a sampling rate of approximately 40 h-1 were obtained.