Use of a Digital Image in Flow Analysis: Determination of Nitrite and Nitrate in Natural Waters

A webcam is proposed as the detector in a flow system with multicommutation, and the feasibility of the approach is demonstrated in the determination of nitrate and nitrite in natural waters. The typical transient signal inherent to the flow system was obtained using a digital video and quantified by ImageJ software. The linear dynamics range for nitrite and nitrate determinations were 0.2 to 2.0 mg L-1 NO2− and 1.0 to 10.0 mg L-1 NO3−, with relative standard deviation < 2% for both analytes. The limits of detection were 0.01 and 0.04 mg L-1 for nitrite for nitrate, respectively, and the s...