Considerations on the use of spectroelectrochemistry in reflection mode for quantitative analysis: Study of the Fe(III)/Fe(II) – orthophenanthroline system

•Spectroelectrochemistry in normal configuration with screen-printed electrodes is a valuable tool for quantitative analysis.•In chronoamperometry the plots of absorbance versus the square root of time are a reliable strategy for quantitation.•Detection limits at micromolar level are achieved for Fe(III) with ortho-phenanthroline as chromogenic reagent.•Spectroelectrochemistry combines two sources of selectivity and could be quite insensitive to the presence of interferences.