Simultaneous flow injection speciation of iron(II) and iron(III) cyano complexes utilizing electrochemical and atomic absorption detectors in series

Summary

A method is described for the simultaneous speciation of Fe(CN) ⁴⁻₆ and Fe(CN) ³⁻₆ in a flow injection (FIA) system comprising electrochemical (EC) and flame atomic absorption spectrometry (AAS) detectors in series. One of these species is detected amperometrically at a Pt-electrode by applying the required potential and measuring the resulting reduction or oxidation current of the appropriate iron cyanide complex. Total iron in both species is determined by an AAS detector. The EC detector is inherently more sensitive, with a detection limit of 0.5 Μg Fe l⁻¹ and a relative standard deviation of 1.0% for a 0.040 Μg Fe ml⁻¹ sample. The limit of detection for the AAS detector is 0.5 Μg Fe ml⁻¹, and the relative standard deviation for a 5.70 Μg Fe ml⁻¹ sample is 0.40%. The method enables up to 60 analyses (120 speciations) per hour and obviates the problem of easy oxidation of Fe(CN) ⁴⁻₆ .