FLOW INJECTION-ASSISTED OPTICAL SENSOR FOR DETERMINATION OF IRON(II) AND IRON(III) IN NATURAL-WATER

An approach for speciation of iron (as Fe(II) and Fe(III)) based on in tegration of retention of the Fe(III)-SCN complex with detection using a conventional spectrophotometer is proposed here. The device (namely , a flow-cell packed with an exchange resin) has been coupled to a flo w-injection manifold with inner-coupled injection valves which enables discrimination between Fe(III) and Fe(II) taking advantage of a redox minicolumn housed in the loop of one of the valves. The method thus p roposed has good selectivity with a determination limit of 80 mu gl(-1 ) and affords a determination range of 80-500 mu gl(-1) for Fe(II) plu s Fe(III). Application to synthetic and real samples containing both t he oxidation states of iron lead to average recoveries of 103% and 101 % for Fe(II) and total iron (Fe(II)+ Fe(III)), respectively, thus show ing the usefulness of the overall approach.