Preconcentration Of Cu Research Articles

Zincon polymer as a new modifier for selective separation and determination of copper and zinc from synthetic, water and drug samples

Chloromethyl polystyrene polymer (CMPSpolymer) has been modified with 2-carboxy-2-hydroxy5-sulfoformazyl benzene (Zincon) to be used as a new reagent for preconcentration of Cu(II) and Zn(II) ions. The modified polymer (Z–polymer) has been characterized by elemental analysis and IR spectra. Batch and column modes were operated. The newly designed polymer sorbs Cu(II) and Zn(II) quantitatively at pH 7 with flow rate of 5 ml min–1. The maximum sorption capacities for Cu(II) and Zn(II) ions were 1.26 and 1.04 mmol g–1. The preconcentration factors were 250 and 200 for Cu(II) and Zn(II) ions. The limit of detection was 4 and 5 ng ml–1 for Cu(II) and Zn(II) ions. The desorption was effective by using 5 ml of 0.1 mol l –1 HCl or HNO3 prior to detection using AAS. The modified polymer was highly ion-selective even in the presence of large concentration of electrolytes or organic media, with a preconcentration ability for Cu(II) and Zn(II) ions. The modified polymer was tested on its utility with synthetic, natural water and drug samples, showing RSD value of < 3% which reflects good accuracy and reproducibility. Keywords: Chloromethyl polystyrene polymer; preconcentration of Cu(II) and Zn(II) ions.

Highly selective preconcentration of Cu(II) from seawater and water samples using amidoamidoxime silica

Chemically modified silica containing amidoamidoxime group was studied as a sorbent for solid-phase extraction (SPE) and preconcentration of Cu(II) prior to determination by flame atomic absorption spectrometry (FAAS). The sorbent showed an extremely high selectivity towards Cu(II) in the pH range of 4–6, while the extraction of Pb(II), Cd(II), Ni(II) and Co(II) was low. The adsorption isotherm followed the Langmuir model and the maximum sorption capacity of 0.0163 mmol Cu(II) g −1 was achieved. In the flow system, Cu(II) was completely retained on a column containing 40 mg of the modified silica at the flow rate of 4.0 mL min −1 and quantitatively eluted by 5 mL of 1% (v/v) HNO 3. No interference from Na +, K +, Mg 2+, Ca 2+, Cl − and SO 4 2− at 10, 100 and 1000 mg L −1 was observed. When applied for preconcentration and determination of Cu(II) in tap water, pond water, and seawater, the recoveries were 96, 101, and 95%, respectively, with high precision (% relative standard deviation (R.S.D.) < 4) and low method detection limit (9 μg L −1).

Selective Removal of Toxic Metals like Copper and Arsenic from Drinking Water Using Phenol‐Formaldehyde Type Chelating Resins

The concentration of different toxic metals has increased beyond environmentally and ecologically permissible levels due to the increase in industrial activity. More than 100 million people of Bangladesh and West Bengal in India are affected by drinking ground water contaminated with arsenic and some parts of India is also affected by poisoning effect of copper, cadmium and fluoride. Different methods have been evolved to reduce the arsenic concentration in drinking water to a maximum permissible level of 10 μg/L where as various methods are also available to separate copper from drinking water. Of the proven methods available today, removal of arsenic by polymeric ion exchangers has been most effective. While chelating ion exchange resins having specific chelating groups attached to a polymer have found extensive use in sorption and pre concentration of Cu2+ ions. Both the methods are coupled here to separate and preconcentrate toxic metal cation Cu2+ and metal anion arsenate(AsO4–) at the same time. We have prepared a series of low‐cost polymeric resins, which are very efficient in removing copper ion from drinking water and after coordinating with copper ion they act as polymeric ligand exchanger, which are efficiently removing arsenate from drinking water. For this purpose Schiff bases were prepared by condensing o‐phenylenediamine with o‐, m‐, and p‐hydroxybenzaldehydes. Condensing these phenolic Schiff bases with formaldehyde afforded the chelating resins in high yields. These resins are loaded with Cu2+, Ni2+ 2+, and Fe3+ ions. The resins and the polychelates are highly insoluble in water. In powdered form the metal ion‐loaded resins are found to very efficiently remove arsenate ion from water at neutral pH. Resins loaded with optimum amount of Cu2+ ion is more effective in removing arsenate ions compared to those with Fe3+ ion, apparently because Cu2+ is a stronger Lewis acid than Fe3+. Various parameters influencing the removal of the arsenate ion from drinking water to a concentration level below 20 μg/L are studied.

On-line preconcentration of copper as its pyrocatechol violet complex on Chromosorb 105 for flame atomic absorption spectrometric determinations

An on-line solid phase extraction method for the preconcentration and determination of Cu(II) by flame atomic absorption spectrometry (FAAS) has been described. It is based on the adsorption of copper(II) ion onto a home made mini column of Chromosorb 105 resin loaded with pyrocatechol violet at the pH range of 5.0-8.0, then eluted with 1 mol L(-1) HNO(3). Several parameters, such as pH of the sample solution, amount of Chromosorb 105 resin, volume of sample and eluent, type of eluent, flow rates of sample and eluent, governing the efficiency and throughput of the method were evaluated. The concentration of the copper ion detected after preconcentration was in agreement with the added amount. At optimized conditions, for 15 min of preconcentration time (30 mL of sample volume), the system achieved a detection limit of 0.02 microg L(-1), with relative standard deviation 1.1% at 0.03 microg mL(-1) copper. The present method was found to be applicable to the preconcentration of Cu(II) in natural water samples.

Optimization and application of homogeneous liquid–liquid extraction in preconcentration of copper (II) in a ternary solvent system

In this study a homogeneous liquid–liquid extraction based on the Ph-dependent phase-separation process was investigated using a ternary solvent system (water–acetic acid–chloroform) for the preconcentration of Cu 2+ ions. 8-Hydroxy quinoline was used as the chelating agent prior to its extraction. Flame atomic absorption spectrophotometry using acetylene-air flame was used for the quantitation of analyte after preconcentration. The effect of various experimental parameters in extraction step was investigated using two optimization methods, one variable at a time and central composite design. The experimental design was done at five levels of operating parameters. Nearly the same optimized results were obtained using both methods: sample size, 5 mL; volume of NaOH 10 M, 2 mL; chloroform volume, 300 μL; 8-hydroxy quinoline concentration more than 0.01 M and salt amount did not affect the extraction significantly. Under the optimum conditions the calibration graph was linear over the range 10–2000 μg L −1. The relative standard deviation was 7.6% for six repeated determinations ( C = 500 μg L −1). Furthermore, the limit of detection (S/N = 3) and limit of quantification (S/N = 10) of the method were obtained as 1.74 and 6 μg L −1, respectively.

Application of a metal ion-imprinted polymer based on salen–Cu complex to flow injection preconcentration and FAAS determination of copper

A new Cu(II)-imprinted polymer (Cu-IIP) for preconcentration of copper by liquid–solid extraction via flow injection technique has been proposed. Cu-IIP was obtained by copolymerization of salen–Cu(II) complex with styrene and divinylbenzene using suspension polymerization technique. Granules fraction of 60–80 μm in diameter was used as a microcolumn packing. Cu(II) sorption was proved to be the most effective from solutions of pH 7, whereas similar elution effectiveness was observed when applying as eluents hydrochloric or nitric acid in the concentration range of 0.5–10% (v/v). The system exhibited good long-term stability and acid resistance. Batch sorbent capacity was found to be 0.11 mmol g −1 of a dry polymer. Enrichment factor (EF) for 30 s loading time was 16. Preconcentration of Cu(II) and potentially interfering metal ions is strongly pH dependent. Examination of Cu(II) sorption in the presence of Pb(II), Cd(II), Zn(II) and Ag(I) showed significant influence of cadmium and zinc ions only and that was for the interferent concentrations above 0.5 mg L −1 (Cu-IIP mass of ca. 35 mg). The interference effect was reduced with the sorbent mass increase. Fe(III) and Mn(II) ions, present in treated tap water in relatively high concentrations, did not interfere. Effective pH adjusting of the loaded solution in on-line mode, when applying diluted Clark–Lubs buffering solution, allowed accurate copper determination in tap water (compared to graphite furnace atomic absorption spectrometry, GFAAS) using standard addition or combination calibration method.

Optimization of dispersive liquid–liquid microextraction of copper (II) by atomic absorption spectrometry as its oxinate chelate: Application to determination of copper in different water samples

In this study a dispersive liquid–liquid microextraction (DLLME) method based on the dispersion of an extraction solvent into aqueous phase in the presence of a dispersive solvent was investigated for the preconcentration of Cu 2+ ions. 8-Hydroxy quinoline was used as a chelating agent prior to extraction. Flame atomic absorption spectrometry using an acetylene-air flame was used for quantitation of the analyte after preconcentration. The effect of various experimental parameters on the extraction was investigated using two optimization methods, one variable at a time and central composite design. The experimental design was performed at five levels of the operating parameters. Nearly the same results for optimization were obtained using both methods: sample size 5 mL; volume of dispersive solvent 1.5 mL; dispersive solvent methanol; extracting solvent chloroform; extracting solvent volume 250 μL; 8-hydroxy quinoline concentration and salt amount do not affect significantly the extraction. Under the optimum conditions the calibration graph was linear over the range 50–2000 μg L −1. The relative standard deviation was 5.1% for six repeated determinations at a concentration of 500 μg L −1. The limit of detection (S/N = 3) was 3 μg L −1.

Column Solid Phase Extraction of Copper and Nickel on Triethylenetetramine Bonded Silica Gel for their Atomic Absorption Spectrometric Determination

A procedure for the preconcentration of Cu(II) and Ni(II) is proposed using a minicolumn filled with silica gel modified by triethylenetetramine. The retained analytes on the modified silica gel were eluted with hydrochloric acid solution. The metal ions in the eluate were determined by flame atomic absorption spectrometry. The effect of various factors, such as pH of the sample solution, sample volume, flow rate of the sample solution, type of eluent, and matrix content of the sample solution, on preconcentration were examined to obtain optimum conditions. The recoveries for Cu(II) and Ni(II) ions under optimum preconcentration conditions were 98.3±1.3 and 99.2±1.4% at 95% confidence level, respectively. The analytical detection limits of Ni and Cu were found to be 0.22 and 0.36 µg L−1, respectively. The proposed method was applied to the determination copper and nickel in river and synthetic sea water.

Efficient Preconcentration of Cu2+, Zn2+ and Fe3+ with an Agarose-Schiff Base Sorbent

Sorption and preconcentration of Cu2+, Zn2+ and Fe3+ on a salen-type Schiff base, 2,2'- [ethane-1,2-diylbis(nitrilomethylidyne)]bis(2-methylphenol), chemically immobilized on a highly crosslinked agarose support, were studied. Kinetic studies showed higher sorption rates of Cu2+ and Fe3+ in comparison with Zn2+. Half-times (t1/2) of 31, 106 and 58 s were obtained for sorption of Cu2+, Zn2+ and Fe3+ by the sorbent, respectively. Effects of pH, eluent concentration and volume, ionic strength, buffer concentration, sample volume and interferences on the recovery of the metal ions were investigated. A 5-ml portion of 0.4 M HCl solution was sufficient for quantitative elution of the metal ions from 0.5 ml of the sorbent packed in a 6.5 mm i.d. glass column. Quantitative recoveries were obtained in a pH range 5.5-6.5 for all the analytes. The volumes to be concentrated exceeding 500 ml, ionic strengths as high as 0.5 mol l-1, and acetate buffer concentrations up to 0.3 mol l-1 for Zn2+ and 0.4 mol l-1 for Cu2+ and Fe3+ did not have any significant effect on the recoveries. The system tolerated relatively high concentrations of diverse ions. Preconcentration factors up to 100 and detection limits of 0.31, 0.16 and 1.73 μg l-1 were obtained for Cu2+, Zn2+ and Fe3+, respectively, for their determination by a flame AAS instrument. The method was successfully applied to the metal ion determinations in several river water samples with good accuracy.

Solid phase extractive preconcentration of trace metals using p- tert-butylcalix[4]arene-1,2-crown-4-anchored chloromethylated polymeric resin beads

5,11,17,23-Tetrakis(1,1-dimethylethyl)-25,26-dihydroxy-27,28-crown-4-calix[4]arene in the cone conformation was synthesized. This p- tert-butylcalix[4]arene-1,2-crown-4 compound was then anchored with Merrifield chloromethylated resin beads. The modified polymeric resin was characterized by 1H NMR, FT-IR and elemental analysis and used successfully for the separation and preconcentration of Cu(II), Cd(II), Co(II), Ni(II) and Zn(II) prior to their determination by FAAS. Effective extraction conditions were optimized in both batch and column methods. The resin exhibits good separating ability with maximum between pH 6.0–7.0 for Cu(II), pH 6.0 for Cd(II), pH 5.0 for Co(II), pH 4.0–4.5 for Ni(II), and pH 4.5 for Zn(II). The elution studies were carried out with 0.5 mol L −1 HCl for Cu(II), Co(II) and Co(II), 1.0 mol L −1 HCl for Cd(II) and Zn(II). The sorption capacity, preconcentration factor and distribution coefficient of each metal ion were determined. The detection limits were 1.10, 1.25, 1.83, 1.68 and 2.01 μg L −1 for Cu(II), Cd(II), Co(II), Ni(II) and Zn(II). The influence of several ions on the resin performance was also investigated. The validity of the proposed method was checked for these metal ions in NIST standard reference material 2709 (San Joaquin Soil) and 2711 (Montana Soil).

Solid phase selective separation and preconcentration of Cu(II) by Cu(II)-imprinted polymethacrylic microbeads

Ion-imprinted polymer (IIP) particles are prepared by copolymerization of methacrylic acid as monomer, trimethylolpropane trimethacrylate as crosslinking agent and 2,2′-azo-bis-isobutyronitrile as initiator in the presence of Cu(II), a Cu(II)–4-(2-pyridylazo)resorcinol (Cu(II)–PAR) complex, and PAR only. A batch procedure is used for the determination of the characteristics of the Cu(II) solid phase extraction from the IIP produced. The results obtained show that the Cu(II)–PAR IIP has the greatest adsorption capacity (37.4 μmol g −1 of dry copolymer) among the IIPs investigated. The optimal pH value for the quantitative preconcentration is 7, and full desorption is achieved by 1 M HNO 3. The selectivity coefficients ( S Cu/Me) for Me = Ni(II), Co(II) are 45.0 and 38.5, respectively. It is established that Cu(II)–PAR IIPs can be used repeatedly without a considerable adsorption capacity loss. The determination of Cu(II) ions in seawater shows that the interfering matrix does not influence the preconcentration and selectivity values of the Cu(II)–PAR IIPs. The detection and quantification limits are 0.001 μmol L −1 (3 σ) and 0.003 μmol L −1 (6 σ), respectively.

Biosorption of copper(II), lead(II), iron(III) and cobalt(II) on Bacillus sphaericus-loaded Diaion SP-850 resin

The biosorption of copper(II), lead(II), iron(III) and cobalt(II) on Bacillus sphaericus-loaded Diaion SP-850 resin for preconcentration–separation of them have been investigated. The sorbed analytes on biosorbent were eluted by using 1 mol L −1 HCl and analytes were determined by flame atomic absorption spectrometry. The influences of analytical parameters including amounts of pH, B. sphaericus, sample volume etc. on the quantitative recoveries of analytes were investigated. The effects of alkaline, earth alkaline ions and some metal ions on the retentions of the analytes on the biosorbent were also examined. Separation and preconcentration of Cu, Pb, Fe and Co ions from real samples was achieved quantitatively. The detection limits by 3 sigma for analyte ions were in the range of 0.20–0.75 μg L −1 for aqueous samples and in the range of 2.5–9.4 ng g −1 for solid samples. The validation of the procedure was performed by the analysis of the certified standard reference materials (NRCC-SLRS 4 Riverine Water, SRM 2711 Montana soil and GBW 07605 Tea). The presented method was applied to the determination of analyte ions in green tea, black tea, cultivated mushroom, boiled wheat, rice and soil samples with successfully results.

Solid Phase Extraction of Trace Metals in Seawater Using Morpholine Dithiocarbamate‐Loaded Amberlite XAD‐4 and Determination by ICP‐AES

Application of morpholine dithiocarbamate (MDTC) coated Amberlite XAD‐4, for preconcentration of Cu(II), Cd(II), Zn(II), Pb(II), Ni(II) and Mn(II) by solid phase extraction and determination by inductively coupled plasma (ICP) atomic emission spectrometry (AES) was studied. The optimum pH values for quantitative sorption of Cu(II), Cd(II), Zn(II), Pb(II), Ni(II), and Mn(II) were 6.5–8.0, 7.0–8.5, 6.0–8.5, 6.5–8.5, 7.5–9.0, and 8.0–8.5, respectively. The metals were desorbed with 2 mol L−1. The t1/2 values for sorption of metal ions were 2.6, 2.9, 2.5, 2.6, 3.0, and 3.8 min respectively for Cu(II), Cd(II), Zn(II), Pb(II), Ni(II) and Mn(II). The effect of diverse ions on the determination of the previously named metals was studied. Simultaneous enrichment of the six metals was accomplished, and the method was applied for use in the determination of trace metal ions in seawater samples.

Simultaneous preconcentration of Cu, Fe and Pb as methylthymol blue complexes on naphthalene adsorbent and flame atomic absorption determination

A simultaneous preconcentration method was developed for determination of trace amounts of Cu, Fe and Pb by atomic absorption spectrometry. The method is based on the retention of their methylthymol blue complexes by naphthalene methyltrioctyl ammonium chloride adsorbent in a column. The adsorbed metal complexes were eluted from the column with nitric acid and Cu, Fe and Pb were determined by flame atomic absorption spectrometry. Several parameters such as pH of the sample solution, ligand concentration, volume of the sample and the amount of methyltrioctyl ammonium chloride loaded on naphthalene were evaluated. The effect of diverse ions on the preconcentration was also investigated. A preconcentration factor of up to 100 or more can easily be achieved depending on the volume of the sample taken. The calibration graphs were obtained in the range of 5–40, 10–100 and 10–200 ng ml −1 for Cu, Fe and Pb in the initial solution, respectively, when using 500 ml of the solution. The detection limit based on three standard deviations of the blank was 0.54, 3.1, and 4.5 ng ml −1 for Cu, Fe and Pb, respectively. The relative standard deviations (R.S.D.) of 0.62–1.4% for Cu, 1.9–3.4% for Fe and 1.0–2.2% for Pb were obtained. The method was applied to the determination of Cu, Fe and Pb in river and wastewater samples.

Use of 1,3-diaminepropane-3-propyl grafted onto a silica gel as a sorbent for flow-injection spectrophotometric determination of copper (II) in digests of biological materials and natural waters

The 1,3-diaminepropane-3-propyl-anchored silica gel (DAPPS) was successfully employed as a sorbent in a spectrophotometric flow system for the preconcentration of Cu 2+ in digests of biological materials (maize powder, soybean, citrus leaves, corn stalks) as well as water samples (river, stream, streamlet, springwater and well). The system presented a minicolumn packed with DAPPS, where the sample solution was passed through it for a period of time, and subsequently, an eluent solution, stripped-out the retained analyte which was further determined with DDTC at 460 nm. The better preconcentration conditions utilized were: 120 s loading, 60 s elution, 30 s regeneration of the column, loading flow rate 6.5 ml min −1, buffer solution for the preconcentration and regeneration of the column-borate buffer pH 8.5, elution flow rate 2.3 ml min −1, time of elution 60 s, eluent composition, 0.4 mol l −1 HNO 3. Under these conditions, the preconcentration factor obtained was 36, and the detection limit achieved was 8.4 ng ml −1 in water samples and 0.84 μg g −1 in biological material. The maximum adsorption capacity of DAPPS to Cu 2+ was 0.49 mmol g −1 (31.1 mg g −1) obtained in a batch system. The recovery of copper in the water samples ranged from 96.9 to 102.4% and in the biological materials ranged from 97.0 to 102.6%.

Chitosan functionalized with 2[-bis-(pyridylmethyl) aminomethyl]4-methyl-6-formyl-phenol: equilibrium and kinetics of copper (II) adsorption

The complexation agent 2[-bis-(pyridylmethyl) aminomethyl]-4-methyl-6-formyl-phenol (HL) was immobilized in chitosan in order to obtain a new adsorbent material to be employed in studies on adsorption and pre-concentration of Cu(II). The chitosan modified by the complexation agent was characterized by infrared spectroscopy, DSC and TGA. The studies were conducted as a function of the pH of the medium and the mechanism of Cu(II) adsorption in the solid phase was analyzed utilizing several kinetic models. The parameters for the adsorption of Cu(II) ions by chitosan–HL were determined with a Langmuir isotherm, the maximum saturation capacity of the monolayer being 109.4 mg of Cu(II) per gram of polymer. Electron paramagnetic resonance spectroscopy revealed that Cu II ions coordinate to the donor atoms of the HL ligand anchored to the surface of the polymer forming a stable chelate complex in the solid state.

Cloud point extraction preconcentration for capillary electrophoresis of metal ions

The application of the cloud point extraction (CPE) technique for capillary electrophoresis (CE) determination of metal ions was demonstrated using Cu(II) and Co(II) as model metal ions. The preconcentration of Cu(II) and Co(II) in aqueous solution was achieved by CPE with 1-(2-pyridylazo)-2-naphthol (PAN) as the chelating agent and Triton X-114 as the extractant. Baseline separation of the PAN chelates of Cu(II) and Co(II) was realized by CE with a photodiaode array detector in a 50 cm×75 μm i.d. fused-silica capillary at 17 kV. A 50 mM NH 4Ac buffer solution (pH 8.0) containing 0.2 mM of PAN in 80% (v/v) of acetonitrile and 20% (v/v) doubly deionized water (DDW) was used as the separation medium to avoid the adsorption of hydrophobic substances and nonionic surfactant Triton X-114 onto the inner surface of the separation capillary, ensuring the separation efficiency and reproducibility. The precision (relative standard deviation (R.S.D.), n=5) for five replicate injections of a mixture of 20 μg/l of Co(II) and Cu(II) were 0.74 and 1.8% for the migration time, 3.1 and 0.64% for the peak area measurement, respectively. The apparent concentration factor, which is defined as the concentration ratio of the analyte in the final diluted surfactant-rich extract ready for CE separation and in the initial solution, was 15.9 for Co(II) and 16.3 for Cu(II). The linear concentration range was from 3 to 100 μg/l for both Co(II) and Cu(II). The detection limits of Co(II) and Cu(II) were 0.12 and 0.26 μg/l, respectively. The developed method was successfully applied to the determination of Co(II) and Cu(II) in tap water, snow water, and flavor wines.

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 p Ka 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 μmol g −1 and follows the order Cd<Pb<Zn<Co<Ni<Fe<Cu. Tolerance limits for electrolytes NaNO 3, NaCl, NaBr, Na 2SO 4 and Na 3PO 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 ≤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.≤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.∼1.4%. The results are in the good agreement with the certified value, 1.99 μg 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%.

STUDY OF THE SELECTIVITY CHARACTERISTICS INCORPORATED INTO PHYSICALLY ADSORBED ALUMINA PHASES. II. MERCAPTONICOTINIC ACID AND POTENTIAL APPLICATIONS AS SELECTIVE STATIONARY PHASES FOR SEPARATION, EXTRACTION, AND PRECONCENTRATION OF LEAD(II) AND COPPER(II)

ABSTRACT A method is described for the immobilization of 2-mercaptonicotinic acid on the surface of three different alumina phases. The selected alumina phases are characterized by different acidity properties, acidic phase (I), neutral phase (II), and basic phase (III). Evidences for the physical adsorption of the organic modifier on the surface of the newly synthesized alumina phases (IV–VI) were evaluated on the basis of infrared spectrophotometric analysis, as well as the surface coverage values and pH values of all alumina phases (I–VI). The determined mmol g−1 values for the modified alumina were found to be 0.886, 1.012, and 0.958 for the modified acidic phase (IV), neutral phase (V), and basic phase (VI), respectively. These alumina phases (I–VI) were extensively investigated to identify the possible selectivity characters incorporated into the modified alumina phases and compared with the unmodified ones. This study was accomplished by the determination of the distribution coefficient value (Kd), as well as the separation factor (α) for a series of mono-, di-, and trivalent metal ions. The results of this study were found to confirm the strong affinity and selectivity of the modified alumina phases (IV–VI) for Pb(II) and Cu(II), due to the noticeably high increase in their separation factors versus other interfering metal ions. The advantage of the selectivity character in the modified phases (IV–VI) was also confirmed by the application of a micro-column for selective separation of Cu(II) and Pb(II) from other interfering metal ions, such as Ca(II), Cr(III), Co(II), and Cd(II). Finally, a micro-column was also used and applied for the selective separation, extraction, and preconcentration of Cu(II) and Pb(II) from sea water samples, and the results indicated good recovery values for the spiked 1.0 ng mL−1 of these two metal ions. The percentage recovery values of Cu(II) and Pb(II) were found to be in the range of 95.2– 98.7±2.0 – 4.0% by the three physically adsorbed alumina phases with 2-mercaptonicotinic acid (IV–VI), with a preconcentration factor of 500.

The application of cloud point preconcentration for the determination of Cu in real samples by flame atomic absorption spectrometry

A simple and practical preconcentration method using cloud point approach is proposed for the extraction and preconcentration of Cu (II). The analyte in the initial aqueous solution, acidified with HCl, is complexed with O, O-diethyldithiophosphate and Triton X-100 is added as a surfactant. After phase separation at 40°C based on cloud point of the mixture and dilution of the surfactant-rich phase with methanol, the enriched analyte is determined by flame atomic absorption spectrometry using conventional nebulization and the analytical wavelength used is 324.8 nm. The variables affecting the complexation and extraction steps were optimized. Under optimum conditions, preconcentration of 10 ml of sample in the presence of 0.1% (v/v) Triton X-100 permitted the detection of 0.94 ng ml −1 of Cu. Analytical graphs were rectilinear in the concentration range of 5–200 ng ml −1 and relative standard deviations were lower than 3%. The method affords recoveries in the range 97–101%. The method was successfully applied to the determination of Cu in drinking and rainwater, serum and human hair samples.