Flow-injection manifold for the simultaneous spectrophotometric determination of Fe(II) and Fe(III) using 2,2'-dipyridyl-2-pyridylhydrazone and a single-line double injection approach.
A simple and rapid flow-injection (FI) method is reported for the simultaneous spectrophotometric determination of Fe(II) and Fe(III) in pharmaceutical products. The method is based on the reaction of Fe(II) with 2,2'-dipyridyl-2-pyridylhydrazone (DPPH) in acidic medium to form a water-soluble reddish complex (lambdamax=535 nm). Fe(III) reacts with DPPH under flow conditions only after its on-line reduction by ascorbic acid (AsA). Both analytes were determined in the same run via a double-injection valve, which enabled the simultaneous injection of two sample volumes in the same carrier stream (,,single-line double-injection" approach). The two well-defined peaks produced corresponded to total iron [Fe(II)+Fe(III)] and Fe(II). Speciation of the analytes in their mixtures was achieved by multiple regression analysis. The calibration curves obtained were linear over the ranges 0-30 and 0-50 mg L(-1) for Fe(II) and Fe(II), respectively, and the precision [s(r)=1.0% for Fe(II) and 1.5% for Fe(III)] was satisfactory. The method proved to be selective and adequately sensitive (cL=0.25 and 0.17 mg L(-1) for Fe(III) and Fe(II), respectively, in mixtures). Application of the method to the analysis of pharmaceutical samples resulted in excellent accuracy; the percent mean recoveries were in the range 99.0-102.0% for both Fe(II) and Fe(III) and the mean relative error was e(r)=1.0%.
Themelis
D G
DG
Department of Chemistry, Aristotle University of Thessaloniki, Greece. themelis@chem.auth.gr
Tzanavaras
P D
PD
Kika
F S
FS
Sofoniou
M C
MC
D015082:2,2'-Dipyridyl / Q000031:analogs & derivatives / Q000737:chemistry*; D002214:Capsules / Q000032:analysis; D005290:Ferric Compounds / Q000032:analysis*; D005296:Ferrous Compounds / Q000032:analysis*; D017022:Flow Injection Analysis / Q000295:instrumentation / Q000379:methods*; D006835:Hydrazones / Q000737:chemistry*; D004364:Pharmaceutical Preparations / Q000032:analysis*; D013053:Spectrophotometry / Q000379:methods; D013607:Tablets / Q000032:analysis
C445219:2,2'-dipyridyl-2-pyridylhydrazone; D002214:Capsules; D005290:Ferric Compounds; D005296:Ferrous Compounds; D006835:Hydrazones; D004364:Pharmaceutical Preparations; D013607:Tablets; D015082:2,2'-Dipyridyl