INTERNATIONAL JOURNAL OF ENVIRONMENTAL ANALYTICAL CHEMISTRY, vol.91, no.5, pp.448-461, 2011 (SCI-Expanded)
A simple speciation, separation and enrichment method has been developed
for the determination of Cr(III) and Cr(VI) ions in different samples by
ion-pair solvent extraction with a -diketone ligand, 2-(4-methoxybenzoyl)-N0-
benzylidene-3-(4-methoxyphenyl)-3-oxo-N-phenyl-propono hydrazide (MBMP).
Cr(III) was separated from Cr(VI) as Cr(III)-(MBMP)-perchlorate ternary
ion-pair complex. The influences of various analytical parameters including pH,
amount of reagent, shaking time, sample volume and ionic strength on the
recovery of Cr(III) and/or Cr(VI) were investigated. Total chromium was
obtained after reducing Cr(VI) to Cr(III) with NH2OH HCl. Recoveries were
found to be higher than 95% and the relative standard deviation (RSD) was less
than 2%. The method detection limit based on 3 criterion for Cr(III) was found
to be 0.32 mg L-1. The formed ternary ion-pair complex, Cr(III) :MBMP: 2ClO4,
has a molar ratio of 1 : 1 : 2. The developed method has been applied successfully
to the speciation of chromium in various natural water, soil, sediment and hair
samples with satisfactory results.