Novel flow injection analysis methods for the determination of total iron in blood serum and water

This work describes rapid, sensitive and highly precise methods for the determination of total iron in blood serum and water samples, using batch, nFIA and rFIA techniques. The proposed methods are based on the selective oxidation of 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) by iron(III). The absorbance of the resultant green solution of radical cation (ABTS ^·+) was monitored spectrophotometrically at λ_max=415 nm. The reaction is stoichiometric with a ratio of 1:1 (Fe(III):ABTS) as determined by Job's and molar ratio methods. The proposed methods allow for the determination of Fe(III) in the ranges 0-4.5 mg L ^-1 (LOD 25.5 μg L^-1, %RSD 0.97%, n=7); 0 to 4.5 mg L^-1 (LOD 370 μg L^-1, %RSD 1.28%, n=7) and 0 to 2.7 mg L^-1 (81.6 μg L^-1, %RSD 0.76%, n=6) for batch, nFIA and rFIA techniques, respectively. The proposed methods show high selectivity to Fe(III), as indicated by the high tolerance limits for common interfering ions. The nFIA method was applied in total iron assay in camel blood serum, whereas batch and rFIA methods were successful in the determination of total iron in municipal pipeline water and spiked groundwater. Statistical analysis indicated insignificant differences in accuracy and precision between the results obtained by the developed methods and ICP-AES or phenanthroline methods.