Metal ion enrichment with Amberlite XAD-2 functionalized with Tiron: analytical applications
Abstract
Amberlite XAD-2 was functionalized with Tiron (disodium salt
of 1,2-dihydroxybenzene-3,5-disulfonic acid) by coupling it through an
–NN– spacer. The resulting chelating resin,
characterized by elemental analyses, thermogravimetric analysis and
infrared (IR) spectra, was used to preconcentrate CuII,
CdII, CoII, NiII, PbII,
ZnII, MnII, FeIII and
UO2II. They were determined by flame atomic
absorption spectrometry, except for uranium, for which fluorimetry was
used. The pH ranges for quantitative sorption were 4.0–6.0,
4.5–6.0, 5.0–7.0, 5.0–6.0, 4.0–5.5, 5.0–6.0,
6.5–7.5, 5.0–6.0 and 4.5–5.5, for Cu, Cd, Co, Ni, Pb, Zn,
Mn, Fe and U, respectively. All these metal ions can be desorbed (recovery
91–99%) with 4 mol l−1 HNO3 or HCl,
except for uranyl ion, for which only 4 mol l−1
HNO3 is suitable. The sorption capacity of the resin was 14.0,
9.5, 6.5, 12.6, 12.6, 11.1, 10.0, 5.6 and 7.7 mg of metal ion per gram of
resin, respectively, for the nine metals. The loading half time
(t1/2) was less than 5 min for all the metal ions. The
effects of NaF, NaCl, NaNO3, Na2SO4, and
Na3PO4 on the sorption of these metal ions (0.2 μg
ml−1) are reported. CaII and MgII
are tolerated with each of them (0.2 μg ml−1) up to a
concentration level of 2–30 and 2–10 mmol l−1,
respectively. The enrichment factors for CuII, CdII,
CoII, NiII, PbII, ZnII,
MnII, FeIII and UO2II were 200,
50, 55, 150, 25, 180, 65, 80 and 150 (concentration level 2–25 μg
l−1), respectively. The limits of detection for these
metal ions are 2.0, 1.3, 5.0, 4.0, 24.0, 0.5, 2.5, 5.0 and 1.0 μg
l−1, respectively. Simultaneous enrichment and
determination of all the metal ions is possible. The flame AAS method was
applied to determine these metal ions (except uranyl ion) in river water
samples (RSD ⩽8%) after their enrichment with the present matrix.
Uranium in well water samples and cobalt contents of pharmaceutical vitamin
tablets were also determined fluorimetrically (RSD <5%) and by flame AAS
(RSD ≡3%), respectively, after enrichment on the present resin.