Interference of high salt concentrations in spectrophotometric flow injection analysis is described. The spectrophotometric determination of nitrite with Griess reagent was used as a test model. Several percentage concentrations of sodium chloride, magnesium chloride, or magnesium sulfate solutions caused more than 10% positive interference in determining 0.040 mg L-1 nitrite. This interference was attributed not only to the schlieren effect but to the salt effect, i.e., the accelerated reaction of nitrite with the Griess reagent
