Simultaneous Determination of Iron(III) and Cobalt(II) with N-Phenyleinnamohydroxamie Acid (PCllA) and Thiocyanate and De-termination of Iron(III) I'lith PCHA o.nd Azide by Solvent Extraction and Spectrophotometry
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Date
1986-06
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Addis Ababa Universty
Abstract
Iron(III) and cobalt(II) have been found to react
Ivith thiocyana-te in the presence of N-phenyleinnamohydroxamic
acid to form pinkish red and blue colored compl(exes, respectively.
Both the complexes I-lere found to be quantitativfely
extractable into ethylacetate from 0.5-1.5 M hydrochloric
acid solutions. The spectra of iron(III) and cobalt(II)
complexes exhibited absorption maxima in the visible region
at 495 and 625 nm Hith molar absorptivitles of 1800.0 and
-1 -1 1820 1 mol ern , respectively. The coloured systems obeyed
Beer! s laH in the concentration loange of 0.2- 3.9 ppm of iron
and 2-41 ppm of cobalt. The composition of the complexes
have been found to be 1:2:2 (Fe:SCN-:PCHA) and 1:4 (Co:SCN-).
The effect of foreign ions and other experimental variables
in the extraction and determination of iron(III) and cobalt
(II) have been studied. On the basis of these studies
simple, precise, sensitive, and highly selective methods
have been developed for the determination of iron(III) and cobal t (II) and for the simultaneous determination of both
metal ions by solvent extraction and spectrophotometry.
The methods have been applied successfully for the determination
of iron and cobalt in steel and biosamples.
Iron(III) was also found to react with azide in the
presence of PCHA to produce an orange coloured complex
having a composition of 1:2:2 (Fe:N;:PCHA). The complex
was found to be stable and quantitatively extractable into
ethylacetate from 0.1-0.9 11 Hel solutions allol-ling repro··
ducible and reliable spectrophotometric determination of
iron. The complex has maximum absorption at 447 nm I-lith
-J -1 molar absorptivity of 7500 1 mol 'cm and obeyed Beer's
law in the range of 0.5-9 ppm of iron(III). From the study
of the effect of foreign ions and several variables, the
method I-Ias found to be highly selective and largely free
from rigid control of experimental variablcs. The method
vias found to be effective by applying for the determination
of iron in blood and s"teel samples. Thus, a new rapid,
precise, sensitive and highly selective method for determination
of iron(llI) with PCHA and azide has bean developed
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Keywords
Iron(III) and cobalt(II)