Flow injection analysis of trace amounts of iron with 2-nitroso-5-(<I>N</I>-ethyl-<I>N</I>-sulfopropylamino)phenol

Abstract

Spectrophotometric determination of trace amounts of iron by flow injection analysis was investigated. Iron (II) forms a water-soluble chelate with 2-nitroso-5-(N-ethyl-N-sulfopropyl-amino)phenol (nitroso-ESAP). Carrier solution (2.0 × 10-4 M ascorbic acid in buffer solution, pH 7) and reagent solution (1.5 × 10-4 M nitroso-ESAP in buffer solution, pH 7) were propelled by double plunger pump (flow rate, P1 : 1.4 ml/min, P2 : 1.2 ml/min), and a sample solution (150 μl) was injected into a carrier stream via a loopvalve sample injector. The carrier stream met a reagent stream and flowed together into a reaction coil (0.5 mm i.d. × 10 m). The absorbance was measured at 752 nm. Calcium (II), cadmium(II), magnesium(II), aluminium (III), zinc(II), mercury(II), silver(I), lead(II), and nickel(II) did not interfere with determination of iron. Chromium(III) and copper(II) gave an interference, but the interference of copper was depressed by addition of ammonium buffer solution in reagent solution. Sampling rate was 20 samples per h. The relative standard deviation was about 0.5 %. The flow injection system could be applied to the determination of total iron in water and serum samples.