Ajai K. Singh

Amberlite XAD-2 functionalized with o-aminophenol: synthesis and applications as extractant for copper(II), cobalt(II), cadmium(II), nickel(II), zinc(II) and lead(II)

A stable chelating resin matrix was synthesized by covalently linking o-aminophenol (o-AP) with the benzene ring of the polystyrene-divinylbenzene resin, Amberlite XAD-2, through a -NN- group. Elemental analyses, thermogravimetric analysis (TGA) and infrared spectra have characterized the resulting chelating resin. It has been used to preconcentrate Cu(2+), Cd(2+), Co(2+), Ni(2+), Zn(2+) and Pb(2+), prior to their determination by flame atomic absorption spectrometry. The optimum pH values for quantitative sorption of Cu, Cd, Co, Ni, Zn and Pb are 6.2-7.4, 5.6-7.2, 5.6-9.0, 6.0-9.0, 5.7-7.0 and 5.0-6.0, respectively. These metals are desorbed (recovery 91-98%) with 4 mol dm(-3) HNO(3). The sorption capacity of the resin is 3.37, 3.42, 3.29, 3.24, 2.94 and 3.32 mg of metal g(-1) of resin, respectively, for Cu, Cd, Co, Ni, Zn and Pb. The effect of NaF, NaCl, NaNO(3), Na(2)SO(4), and Na(3)PO(4) on the sorption of these metal ions has been investigated. These electrolytes are tolerable up to 0.01 mol dm(-3) in case of all the metal ions, except Cl(-) which is tolerable even up to 0.1 mol dm(-3) for Zn and 1.0 mol dm(-3) for Pb. The preconcentration factor for Cu, Cd, Co, Ni, Zn and Pb are 50, 50, 100, 65, 40 and 40 (concentration level 10-25 mug dm(-3)) respectively. Simultaneous enrichment of the six metals is possible. The method has been applied to determine Cu, Cd, Co, Ni, Zn and Pb content in well water samples (RSD</=8%).

Synthesis, characterization and applications of pyrocatechol modified amberlite XAD-2 resin for preconcentration and determination of metal ions in water samples by flame atomic absorption spectrometry (FAAS).

A new chelating resin is prepared by coupling Amberlite XAD-2 with pyrocatechol through an azo spacer, characterized (by elemental analysis, IR and TGA) and studied for preconcentrating Cd(II), Co(II), Cu(II), Fe(III), Ni(II) and Zn(II) using flame atomic absorption spectrometry (FAAS) for metal monitoring. The sorption is quantitative in the pH range 3.0-6.5, whereas quantitative desorption occurs instantaneously with 2 M HCl or HNO(3) The sorption capacity has been found to be in the range 0.023-0.092 mmol g(-1) of resin. The loading half time (t(1/2)) is 1.4, 4.8, 1.6, 3.2, 2.3 and 1.8 min, respectively for Cd, Co, Cu, Fe, Ni and Zn. The tolerance limits of electrolytes NaCl, NaBr, NaNO(3), Na(2)SO(4) and Na(3)PO(4) in the sorption of all the six metal ions (0.2 mug ml(-1)) are reported. The Mg(II) and Ca(II) are tolerable with each of them (0.2 mug ml(-1)) up to a concentration level of 0.01-1.0 M. The enrichment factor has been found to be 200 except for Fe and Cu for which the values are 80 and 100, respectively. The lowest concentration of metal ion for quantitative recovery is 5, 10, 20, 25, 10 and 10 mug l(-1) for Cd, Co, Cu, Fe, Ni and Zn, respectively. The simultaneous determination of all these metal ions is possible and the method has been applied to determine all the six metal ions in tap and river water samples (RSD</=3.9 and 7.3%, respectively). The cobalt content of pharmaceutical vitamin tablets is estimated by FAAS (RSD approximately 2%) after its preconcentration with the present chelating resin.

Preconcentration of lead with Amberlite XAD-2 and Amberlite XAD-7 based chelating resins for its determination by flame atomic absorption spectrometry.

Four chelating matrices prepared by coupling Amberlite XAD-2 with chromotropic acid (AXAD-2-CA or 1), pyrocatechol (AXAD-2-PC or 2) and thiosalicylic acid (AXAD-2-TSA or 3) through azo spacer and impregnation of Amberlite XAD-7 with xylenol orange (AXAD-7-XO or 4) have been studied for enrichment of lead(II). All the four resins quantitatively sorb Pb(II) at pH 3.0-8.0 when the flow rate is maintained between 2 and 10 mlmin(-1). HNO(3) (0.5-4.0 M) instantaneously elutes Pb(II) from all the four chelating resins. The sorption capacity is in the range 16.0-186.0 mumolg(-1) and loading half time (t(1/2)) between 3.2 and 15.5 min. The tolerance limits of electrolytes (NaCl, NaBr, NaNO(3), Na(2)SO(4), Na(3)PO(4)) and cations (Ca and Mg) are reported. Phosphate interferes in the sorption with 3 and 4. The limit of detection and limit of quantification have been found to be in the ranges 2.44-7.87 and 2.76-8.64 ngml(-1), respectively. Lead has been determined in river (RSD approximately 2.6-12.8%) and tap (RSD approximately 1.8-7.2%) water samples.

Metal ion enrichment with Amberlite XAD-2 functionalized with Tiron: analytical applications

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.

Recent developments in the ligand chemistry of tellurium

Abstract The synthesis and coordination chemistry of telluroether (including hybrid ones), anionic organotellurium and inorganic tellurium (halotellurium, telluride and polytellurides) ligands developed during the last decade are reviewed. The characterization of the metal–tellurium bond containing species by multinuclei NMR (particularly 125 Te-NMR) and X-ray diffraction on their single crystals are discussed more emphatically. The ligation of tellurium is compared with other donor sites.

8-Hydroxyquinoline anchored to silica gel via new moderate size linker: synthesis and applications as a metal ion collector for their flame atomic absorption spectrometric determination

The silica gel modified with (3-aminopropyl-triethoxysilane) was reacted with 5-formyl-8-hydroxyquinoline (FHOQ(x)) to anchor 8-quinolinol ligand on the silica gel. It was characterised with cross polarisation magic angle spinning (CPMAS) NMR and diffuse reflectance infrared Fourier transformation (DRIFT) spectroscopy and used for the preconcentration of Cu(II), Pb(II), Ni(II), Fe(III), Cd(II), Zn(II) and Co(II) prior to their determination by flame atomic absorption spectrometry. The surface area of the modified silica gel has been found to be 227 m(2) g(-1) and the two pKa values as 3.8 and 8.0. The optimum pH ranges for quantitative sorption are 4.0-7.0, 4.5-7.0, 3.0-6.0, 5.0-8.0, 5.0-8.0, 5.0-8.0 and 4.0-7.0 for Cu, Pb, Fe, Zn, Co, Ni and Cd, respectively. All the metals can be desorbed with 2.5 mol l(-1) HCl or HNO(3). The sorption capacity for these metal ions is in range of 92-448.0 micromol g(-1) and follows the order Cd<Pb<Zn<Co<Ni<Fe<Cu. Tolerance limits for electrolytes NaNO(3,) NaCl, NaBr, Na(2)SO(4) and Na(3)PO(4), glycine, sodium citrate, EDTA, humic acid and cations Ca(II), Mg(II), Mn(II) and Cr(III) in the sorption of all the seven metal ions are reported. The preconcentration factors are 150, 250, 200, 300, 250, 300 and 200 for Cd, Co, Zn, Cu, Pb, Fe and Ni, respectively and t(1/2) values <1 min except for Ni. The 95% extraction by batch method takes < or =25 min. The simultaneous enrichment and determination of all the metals are possible if the total load of the metal ions is less than sorption capacity. In river water samples all these metal ions were enriched with the present ligand anchored silica gel and determined with flame atomic absorption spectrometer (R.S.D.< or =6.4%). Cobalt contents of pharmaceutical samples (vitamin tablet) were preconcentrated with the present chelating silica gel and estimated by flame AAS, with R.S.D. approximately 1.4%. The results are in the good agreement with the certified value, 1.99 microg g(-1) of the tablets. Iron and copper in certified reference materials (synthetic) SLRS-4 and SLEW-3 have been enriched with the modified silica gel and estimated with R.S.D.<5%.

Pyrocatechol Violet immobilized Amberlite XAD-2: synthesis and metal-ion uptake properties suitable for analytical applications

Abstract Amberlite XAD-2 has been functionalized by coupling it, through the NN group, with Pyrocatechol Violet (PV), and the resulting resin has been characterized by elemental analysis, thermogravimetric analysis (TGA) and IR spectra. The resin has been used for preconcentrating Zn(II), Cd(II), Pb(II) and Ni(II) ions prior to their determination by flame atomic absorption spectrometry. The optimum pH values for quantitative sorption are 5, 5–7, 4, and 3 for Zn, Cd, Pb and Ni, respectively. The four metals can be desorbed (recovery ~98%) with 4 M HNO 3 ; also, 4 M HCl is equally suitable except for Zn. The sorption capacity of the resin is 1410, 1270, 620 and 1360 μg g −1 resin for Zn, Cd, Ni and Pb, respectively. The effect of F − , Cl − , NO 3 − , SO 4 2− and PO 4 3− on the sorption of these four metal ions has been investigated. They are tolerable in the range 0.01–0.20 M, for Pb. In the sorption of Zn(II) and Ni(II), the tolerance limits of all these ions are upto 0.01 M, whereas for Cd(II), F − , NO 3 − , and PO 4 3− have been found to be tolerable upto 0.50, 0.10 and 0.10 M, respectively. The preconcentration factors are 60, 50, 23 and 18 for Zn, Cd, Pb and Ni, respectively. Simultaneous collection and determination of the four metals are possible. Cations commonly present in drinking water do not affect the sorption of either metal ion if present at a concentration level similar to that of water. The method has been applied to determine Zn, Ni and Pb content of well-water samples (RSD ≤9%).

Synthesis of a chelating polymer matrix by immobilizing Alizarin Red-S on Amberlite XAD-2 and its application to the preconcentration of lead(II), cadmium(II), zinc(II) and nickel(II)

A very stable chelating resin matrix was synthesized by covalently linking Alizarin Red-S with the benzene ring of the polymer Amberlite XAD-2 through an −NN− group. The resin was characterized by elemental analyses, thermogravimetric analysis and IR and reflectance spectra. One dye molecule was found to be present per repeat unit of the polymer. The resin was used for the preconcentration of Zn(II), Cd(II), Ni(II) and Pb(II) prior to their determination by flame atomic absorption spectrometry (AAS). For the quantitative sorption and recovery of Zn, Cd, Ni and Pb the optimum pH and eluents were pH 5–6 and 4 M HCl or 1 M HNO3 for Zn, pH 5–6 and 4 M HNO3 for Cd, pH 3–4 and 4 M HCl or 2 M HNO3 for Ni and pH 6 and 3–4 M HNO3 for Pb. The sorption capacity of the resin was 511, 124, 139 and 306 μg per gram of the resin for Zn, Cd, Ni and Pb, respectively. Tolerance limits of NaF, NaCl, Na2SO4, Na3PO4 and NaNO3 on the sorption of these metal ions are reported. Sodium nitrate interfered in the sorption of all the metal ions except Pb(II). The preconcentration factor was 40 for all four metals and the lower limit of preconcentration was 0.01 mg dm−3. The simultaneous determination of all the four cations is possible. The relative standard deviation (R.S.D.) is in the range 3.7–8.2%. Zn, Cd, Ni and Pb in well-water samples were determined by AAS after preconcentrating them with the resin. Ni and Cd were found to be absent. The R.S.D. was 2.7–6.5% and 4.7–10.1% for zinc and lead, respectively.

Thiosalicylic acid-immobilized Amberlite XAD-2: metal sorption behaviour and applications in estimation of metal ions by flame atomic absorption spectrometry

Thiosalicylic acid (TSA)-modified Amberlite XAD-2 (AXAD-2) was synthesized by coupling TSA with the support matrix AXAD-2 through an azo spacer. The resulting chelating resin was characterized by elemental analyses, thermogravimetric analysis (TGA) and infrared spectra. The newly designed resin quantitatively sorbs CdII, CoII, CuII, FeIII, NiII and ZnII at pH 3.5-7.0 when the flow rate is maintained between 2 and 4 ml min-1. The HCl or HNO3 (2 mol l-1) instantaneously elutes all the metal ions. The sorption capacity is 197.5, 106.9, 214.0, 66.2, 309.9 and 47.4 mumol g-1 of the resin for cadmium, cobalt, copper, iron, nickel and zinc, respectively, whereas their preconcentration factor is between 180-400. The breakthrough volume of HCl or HNO3 for elution of these metal ions was found to be 4-8 ml. The limit of detection (LOD) for CdII, CoII, CuII, FeIII, NiII and ZnII was 0.48, 0.20, 4.05, 0.98, 1.28 and 3.94 micrograms l-1, respectively, and the limit of quantification (LOQ) was found to be 0.51, 0.29, 4.49, 1.43, 1.58 and 4.46 micrograms l-1, respectively. The loading half time, t1/2, for the cations was found to be less than 2.0 min, except for nickel for which the value was 13.1 min. The determination of each of these six cations is possible in the presence of other five, if their concentration is up to 4 times. All six metals were determined in river water (RSD approximately 0.7-7.7%) and tap water samples (RSD approximately 0.3-5.7%). The estimation of Co was made in the samples of multivitamin tablets (RSD < 2.3%). The results agree with those quoted by manufacturers.

Amberlite XAD-2 functionalized with chromotropic acid: synthesis of a new polymer matrix and its applications in metal ion enrichment for their determination by flame atomic absorption spectrometry

Chromotropic acid has been covalently linked with the benzene ring of Amberlite XAD-2, through an –NN– group, to design a new polymer matrix. Elemental analyses, thermogravimetric analyses and infrared spectra were used to characterize the resulting functionalized Amberlite XAD-2. It was used for the separation and preconcentration of CdII, CoII, CuII, NiII, FeIII and ZnII prior to their determination by flame atomic absorption spectrometry. The optimum pH values for quantitative sorption are 5.0–6.0, 4.0–4.5, 4.5–5.5, 4.0–5.0, 5.0–6.5 and 5.5–7.0 for CdII, CoII, CuII, FeIlI, NiII and ZnII, respectively. All these metal ions can be desorbed with 2 mol l–1 HCl or HNO3 (recovery, 96–100%). The sorption capacity of the resin is 9.35, 3.84, 8.50, 3.24, 6.07 and 9.65 mg g–1 of resin for Cd, Co, Cu, Ni, Fe and Zn, respectively. Tolerance limits for electrolytes NaCl, NaBr, NaNO3, Na2SO4 and Na3PO4 on the sorption of these metal ions are reported. NaNO3, Na2SO4 and Na3PO4 are tolerable up to a concentration level of a few millimoles in the sorption of 0.1 mg l–1 Cd. Similarly, NaNO3 with Cu (0.1 mg l–1) and Na3PO4 with Fe (0.1 mg l–1) interfere when their concentration exceeds a few millimoles. The enrichment of all of these metal ions is quantitative in the presence of 0.1 mol l–1 of MgII and CaII. The preconcentration factors are found to be 100, 150, 100, 120, 200 and 200 for Cd, Co, Cu, Fe, Ni and Zn (concentration level, 5–10 µg l–1), respectively, and their respective t1/2 values are 2.6, 4.3, 2.9, 5.8, 3.4 and 2.4 min. The simultaneous determination of Cd, Co, Cu, Fe, Ni and Zn is possible. The method was applied to the determination of these six metal ions in river water samples (RSD < 7.8%). Cobalt contents of pharmaceutical samples (vitamin tablets) were preconcentrated by the present chelating resin and estimated by flame atomic absorption spectrometry, with RSD < 1.1%.