Characterization and sensing properties of a carbon nanotube paste electrode for acetaminophen

New separation and preconcentration procedures based on the coprecipitation of Fe(III) and Pb(II) ions with Cu(II) salicylaldoxime coprecipitant and of Cu(II) with Ni(II) salicylaldoxime coprecipitant were studied comparatively. The coprecipitation conditions for each method, such as the effect of the pH, the amounts of carrier elements and reagent, sample volume and matrix effects were examined in detail. The determinations of analyte ions were performed by flame AAS. Under optimised conditions the detection limits of the methods (3s/b) were 1.58, 3.56 and 1.32 μg L^?1 for iron(III), lead(II) an copper(II), respectively. The precision (as RSD %) of the methods was ≤3.2%. Each method was validated by both spiked tap water, dam water samples and by the analysis of certified reference material (TMDA-54.4 fortified lake water). It was found that the recovery of Fe(III), Pb(II) and Cu(II) from the water samples was ≥90%.     

Determination of Metal Ions in Natural Waters by Flame-AAS after Preconcentration on a 5-Amino-1,3,4-Thiadiazole-2-Thiol Modified Silica Gel.

ABSTRACT

5-amino-1,3,4-thiadiazole-2-thiol groups attached on a silica gel surface have been used for adsorption of Cd(II), Co(II), Cu(II), Fe(III), Ni(II), Pb(II) and Zn(II) from aqueous solutions. The adsorption capacities for each metal ion were (in mmol.g^?1): Cd(II)= 0.35, Co(II)= 0.10, Cu(II)= 0.15, Fe(III)= 0.20, Hg(II)= 0.46, Ni(II)= 0.16, Pb(II)= 0.13 and Zn(II)= 0.15. The modified silica gel was applied in the preconcentration and quantification of trace level metal ions present in water samples (river, and bog water).     

1-(2-Formamidoethyl)-3-phenylurea functionalized activated carbon for selective solid-phase extraction and preconcentration of metal ions

A novel method that utilizes 1-(2-formamidoethyl)-3-phenylurea-modified activated carbon (AC-1-(2-formamidoethyl)-3-phenylurea) as a solid-phase extractant has been developed for simultaneous preconcentration of trace Cr(III), Cu(II), Fe(III) and Pb(II) prior to the measurement by inductively coupled plasma atomic emission spectrometry (ICP-AES). Experimental conditions for effective adsorption of trace levels of Cr(III), Cu(II), Fe(III) and Pb(II) were optimized using batch and column procedures in detail. The optimum pH value for the separation of metal ions simultaneously on the new sorbent was 4. And the adsorbed metal ions could be completely eluted by using 2.0 mL 2.0 mol L⁻¹ HCl solution. Common coexisting ions did not interfere with the separation and determination of target metal ions. The maximum static adsorption capacity of the sorbent at optimum conditions was found to be 39.8, 39.9, 77.8 and 17.3 mg g⁻¹ for Cr(III), Cu(II), Fe(III) and Pb(II), respectively. The detection limits of the method were found to be 0.15, 0.41, 0.27 and 0.36 ng mL⁻¹ for Cr(III), Cu(II), Fe(III) and Pb(II), respectively. The relative standard deviation (RSD) of the method was lower than 4.0% (n = 8). The method was successfully applied for the preconcentration of trace Cr(III), Cu(II), Fe(III) and Pb(II) in natural and certified samples with satisfactory results.     

Pre-column chelation liquid chromatographic separation and determination of trace V,Cu, Co,Pd, Fe and Ni

Conditions for the separation by reversed-phase liquid chromatography (LC) of V(V), Cu(II), Co(III), Pd(II), Fe(III) and Ni(II) chelates with 2-(5-bromopyridylazo)-5-diethylaminophenol (5-Br-PADAP) were studied. Six species of metal chelates were separated successfully with methanol-acetonitrile-water (72:12:16, v/v/v) containing 0.13 M NaCl and 0.29 mM cetyltrimethylammonium bromide (pH 5.0) as the mobile phase on a Nucleosil C₁₈ (5 μm) column (250 × 4 mm i.d.).The conditions of the determination of these metal chelates are discussed. A simple and rapid method for the determination of trace amounts of V(V), Cu(II), Co(III), Pd(II) and Ni(II) simultaneously by reversed-phase LC has been developed. The detection limits are 5 × 10^?12, 1 × 10^?10, 3 × 10^?11, 5.3 × 10^?9 and 2 × 10^?10 g, respectively. The method is applied to the determination of these metals in natural waters and mineral samples.     

Column preconcentration and FAAS determination of copper,iron, nickel and zinc using 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol-tetraphenylborate-naphthalene adsorbent

A solid co-precipitated material obtained from an ion-pair of 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) and tetraphenylborate (TPB), and microcrystals of naphthalene has been tried as an adsorbent for the column preconcentration of copper(I), iron(II), nickel(II) and Zn(II). The retention of the metal ions was found to be maximum and constant in the pH range 3.0-8.0 for Cu, 3.8-7.5 for Fe, 4.5-7.5 for Ni and 8.5-11.0 for Zn. The elements were determined by FAAS after dissolving the metal along with the adsorbent in an organic solvent (10 mL of DMF). The characteristic concentration for 1% absorption was found to be 0.0332, 0.0536, 0.0537 and 0.0142 (aqueous medium 0.0512, 0.0638, 0.1294 and 0.0216) microg mL(-1) for Cu, Fe, Ni and Zn, respectively. The calibration plot was linear in the range 1.5-20.0, 2.0-38.0, 2.5-25.0 and 0.5-15.0 micro g in the final 10 mL of DMF solution for Cu, Fe, Ni and Zn, respectively. Various parameters such as pH, volume of buffer, amount of adsorbent, flow rate, preconcentration factor and effect of diverse salts and cations were studied. The optimised conditions were utilized for the determination of Cu, Fe, Ni and Zn in various water, beverage and human hair samples.     

ICP-AES determination of trace elements after preconcentrated with p-dimethylaminobenzaldehyde-modified nanometer SiO2 from sample solution

A new method that utilizes p-dimethylaminobenzaldehyde-modified nanometer SiO₂ (SiO₂-p-DMABD) as a solid phase extractant has been developed for simultaneous preconcentration of trace Cr(III), Cu(II), Fe(III) and Pb(II) prior to the measurement by inductively coupled plasma atomic emission spectrometry (ICP-AES). The preconcentration conditions of analytes were investigated, including the pH value, the shaking time, the mass of sorbent, the sample flow rate and volume, the elution condition and the interfering ions. The adsorption capacity of nanometer SiO₂-p-DMABD was found to be (mg g^− 1) Cr(III): 6.2, Cu(II): 18.6, Fe(III): 4.7 and Pb(II): 6.0 at pH 4. The adsorbed metals were quantitatively eluted with 4 mL of 1.0 mol L^− 1 HCl. According to the definition of IUPAC, the detection limits (3σ) of this method for Cr(III), Cu(II), Fe(III) and Pb(II) were 0.79, 1.27, 0.40 and 1.79 ng mL^− 1, respectively. The proposed method achieved satisfied results when it was applied to the determination of trace Cr(III), Cu(II), Fe(III) and Pb(II) in biological and water samples.     

Preconcentration/Separation of Some Metal Ions Using Sodium Dodecyl Sulfate Coated Alumina Modified with Bis(5‐bromo‐2‐hydroxy‐benzaldehyde)‐2‐methyl‐1,5‐pentane Diimine (BBHBPDI) Prior to Their Flame‐AAS Determination

Preconcentration/separation of Co(II), Fe(III), Pb(II), Cr(III), Cu(II) and Cd(II) ions using bis(5‐bromo‐2‐hydroxy‐benzaldehyde)‐2‐methyl‐1,5‐pentane diimine (BBHBPDI) on SDS coated alumina has been reported. The influences of the analytical parameters including pH, ligand and SDS amount, type and concentration of eluent and sample volume on metal ions recoveries were investigated. At optimum values of all variables the relative standard deviation are between 2.5–2.7 and preconcentration factor was 375, while recoveries for all understudy metal ions are higher than 95%, determination limits are between 1.5–2.7. The method has been successfully applied to determination of Co(II), Fe(III), Pb(II), Cr(III), Cu(II) and Cd(II) ions content in some real samples.     

Novel phenyl-iminodiacetic acid grafted multiwalled carbon nanotubes for solid phase extraction of iron, copper and lead ions from aqueous medium

We have covalently grafted phenyl-iminodiacetic acid groups onto multi-walled carbon nanotubes via a diazotation reaction. The resulting material was characterized by FT-IR and UV–vis spectroscopy, by TGA, XPS and SEM. It is shown to be a valuable solid-phase extraction adsorbent for the preconcentration of trace quantities of Fe(III), Cu(II) and Pb(II) ion from aqueous solution prior to their determination by ICP-OES. Various factors affectting the separation and preconcentration were investigated. The enrichment factor typically is 100. Under optimized experimental conditions, the maximum adsorption capacities for Fe(III), Cu(II) and Pb (II) are 64.5, 30.5 and 17.0?mg?g-1, respectively, the detection limits are 0.26, 0.15 and 0.18?ng?mL-1, and the relative standard deviations are <2.5% (n?=?6). The new adsorbent shows superior reusability and stability. The procedure was successfully applied to the determination of trace quantities of Fe(III), Cu(II) and Pb (II) in water samples.

Simultaneous determination of Mn(II), Cu(II) and Fe(III) as 2-(5′-bromo-2′-pyridylazo)-5-diethylaminophenol complexes by adsorptive cathodic stripping voltammetry at a carbon paste electrode

A simple and precise square-wave adsorptive cathodic stripping voltammetry (SW-AdCSV) method has been described for simultaneous determination of Mn(II), Cu(II) and Fe(III) in water samples using a carbon paste electrode. In 0.1 mol L⁻¹ acetate buffer (pH 5) containing 50 μmol L⁻¹ of 2-(5′-bromo-2′-pyridylazo)-5-diethylaminophenol (5-Br-PADAP), Mn(II), Cu(II) and Fe(III) were simultaneously determined as metal-complexes with 5-Br-PADAP following preconcentration onto the carbon paste electrode by adsorptive accumulation at +1.0 V (vs. Ag/AgCl/3 M KCl). Insignificant interference from various cations (K⁺, Na⁺, Mg²⁺, Ca²⁺, Al³⁺, Bi³⁺, Sb³⁺, Se⁴⁺, Zn²⁺, Ni²⁺, Co²⁺, Cd²⁺, Pb²⁺, V⁵⁺, Ti⁴⁺ and NH₄⁺), anions (HCO₃⁻, Cl⁻, NO³⁻, SO₄²⁻ and PO₄³⁻) and ascorbic acid was noticed. Limits of detection of 0.066, 0.108 and 0.093 μg L⁻¹ and limits of quantitation of 0.22, 0.36 and 0.31 μg L⁻¹ Mn(II), Cu(II) and Fe(III), respectively, were achieved by the described method. The described stripping voltammetry method was successfully applied for simultaneous determination of Mn(II), Cu(II) and Fe(III) in ground, tap and bottled natural water samples.     

Simultaneous determination of seven metal ions in water samples by solid-phase extraction on polyacrylonitrile activated carbon fibres

A new solid-phase extraction method utilising polyacrylonitrile activated carbon fibres (PAN-ACFs) as adsorbent was developed for the preconcentration of trace metal ions prior to their determination by inductively coupled plasma optical emission spectrometry (ICP-OES). The PAN-ACFs oxidised with nitric acid were characterised by FT-IR, XRD, SEM and BET analysis. Then the resulting PAN-ACFs were used as solid-phase adsorbent for simultaneously determination of trace Al(III), Be(II), Bi(III), Cr(III), Cu(II), Fe(III) and Pb(II) ions in aqueous solutions. The influences of the analytical parameters on the recoveries of the studied ions were investigated. The optimum experimental conditions of the proposed method were pH: 6.0; eluent concentration and volume: 3.0 mL of 1.5 mol L^?1 nitric acid; flow rates of sample and eluent solution: 1.5 mL min^?1. The preconcentration factors were found to be 67 for Al(III), Bi(III); 83 for Cr(III), Cu(II), Fe(III) and 50 for Be(II), Pb(II). The precision of this method was in range of 1.5%~3.5% and the detection limit of this metal ions was between 0.06~1.50 μg L^?1. The developed method was validated by the analysis of a certified reference sample and successfully applied to the determination of trace metal ions in water samples with satisfactory results.     

Preparation, characterization and metal sorption studies of a Chrome-Azurol-S-loaded anion-exchange resin

Chrome Azurol S (CS) was mobilized on an strongly basic anion-exchange resin (Dowex 2 x 4, in Cl(-) form) by batch equilibration. The modified resin was stable in acetate buffer solution and in 0.1 M HCl and H(2)SO(4), but it was readily degraded with 2-6 M HCl and HNO(3). Retention of Ba(II), Sr(II), Ca(II), Mg(II), Al(III), Cr(III), Zn(II), Fe(III), Ti(IV), Mn(II), Co(II), Ni(II), Cu(II), Cd(II) and Pb(II) was studied using the batch equilibration method. The uptake and recovery yields were determined by using inductively-coupled plasma atomic emission spectroscopy (for Mg, Al, Cr, Ti, Fe, Mn, Ni, Zn, Cu, Cd and Pb) and atomic absorption spectrophotometry (for Ba, Sr, Ca and Co). The optimum pH value was established for performing a selective separation of Al(III) from the other metal ions. The sorption capacities of the CS-loaded resing for Al(III), Cr(III), Mg(II) (at pH 6), Fe(III) (at pH 5) and Ti(IV) (at pH 4) were 14, 2.9, 0.3, 3 and 3.9 mumoles g(-1) respectively. On this basis a method for separating Al(III) from other cations was established.     

Chemometric study of selected polychlorinated biphenyls in ambient air of Madrid (Spain)

The formation of Fe(III) and Fe(II) chelates with pyridylazo and thiazolylazo reagents was examined. Optimum conditions for the formation of Fe(III) and Fe(II) chelates with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) were in detail evaluated. The LC method for simultaneous separation of Fe(III) and Fe(II) ions as 5-Br-PADAP chelates was evaluated using the PEEK column with C18 e.c. stationary phase and acetonitrile+water (90:10, v/v) eluent containing the 1x10(-3) mol l(-1) C(12)H(25)SO(3)Na, the ion-pairing reagent, pH 3.4-3.6. The simultaneous determination of 20-500 mug l(-1) Fe(II) ions (detection at 555 nm) and 20-500 mug l(-1) Fe(III) ions (detection at 585 nm) as 5-Br-PADAP chelates (for both ions, detection limit, 18 mug l(-1) for 20 mul loop) was established. The chromatographic method was applied to the water analysis. Although the present method is able to determine both Fe(III) and Fe(II) ions, the Fe(III) ion was not detected in all water samples. The Fe(II) was detected only in fresh gathered oligocene water at the level of 135 mug l(-1). The present method was used to the investigation of the distribution of Fe(III)/Fe(II) ions in aqueous and micellar solutions after action of external, ultrasonic field.     

Use of clinoptilolite loaded with 1-(2-pyridylazo)-2-naphthol as a sorbent for preconcentration of Pb(II), Ni(II), Cd(II) and Cu(II) prior to their determination by flame atomic absorption spectroscopy

A solid phase extraction system for separation and preconcentration of trace amounts of Pb(II), Ni(II), Cd(II) and Cu(II) is proposed. The procedure is based on the adsorption of Pb²⁺, Ni²⁺, Cd²⁺ and Cu²⁺ ions on a column of 1-(2-pyridylazo)-2-naphthol (PAN) immobilised on surfactant-coated clinoptilolite prior to their determinations by Flame Atomic Absorption Spectroscopy (FAAS). The effective parameters including pH, sample volume, sample flow rate and eluent flow rate were also studied. The analytes collected on the column were eluted with 5 mL of 1 mol L^?1 nitric acid. A concentration factor of 180 can be achieved by passing 900 mL of sample through the column. The detection limits (3 s) for Cd, Cu, Pb and Ni were found to be 0.28, 0.12, 0.44 and 0.46 µg L^?1, respectively. The relative SDs at 10 µg L^?1 (n = 10) for analytes were in the range of 1.2–1.4%. The method was applied to the determination of Pb, Ni, Cd and Cu in water samples.     

Micro volume changes due to Pb(II) and Cu(II) sorption on amorphous Fe(III) hydroxide

Micro volume changes due to Pb(II) and Cu(II) sorption on amorphous Fe(III) hydroxide (AFH) were determined by a dilatometer at pH 4.50. Volume change is attributed to change in hydration status of dissolved and/or suspended substances. The volume of the system increased due to Pb(II) and Cu(II) sorption, suggesting that water molecules hydrated around Pb(II) or Cu(II) ions and AFH were released during sorption. Volume increases due to Pb(II) and Cu(II) sorption were smaller than those due to bulk precipitation of Pb and Cu hydroxides. Precipitation of Pb(II) and Cu(II) was not likely to occur at pH 4.50 in the presence of AFH. In conclusion, Pb(II) and Cu(II) formed an inner-sphere complex on AFH at pH 4.50, keeping hydrated water on the adsorbed species. Adsorbed Cu(II) kept more hydrated water than adsorbed Pb(II) on AFH.     

Fe(Ⅲ)-5-Br-PADAP络合物光化学还原反应的研究

研究了溶液酸度、光强度、有机酸及其浓度对Fe(Ⅲ)-5-Br-PADAP络合物光化学还原反应的影响,并对该光化学还原反应的机理作了初步探讨.结果表明,在pH为5.5的HAc-NaAc缓冲溶液中,Fe(Ⅲ)-5-Br-PADAP络合物的光化学还原反应速度较快;光强度增加,该光化学还原反应速度加快;甲酸等有机酸能加速该光化学还原反应;乙二酸、丙二酸能明显抑制该光化学还原反应;能促进反应的有机酸浓度增加,该光化学还原反应的速度加快.     

Synthesis, characterisation and evaluation of polydithiocarbamate resin supported on macroreticular styrene-divinylbenzene copolymer for the removal of trace and heavy metal ions

A new chelating resin was synthesised by the modification of styrene-divinylbenzene (2%) copolymer and incorporation of dithiocarbamate groups. The polydithiocarbamate resin was characterised by elemental analysis, thermal studies and IR studies. The analytical characteristics of the sorbent were established and optimum sorption conditions for Cu, Ni, Pb, Fe, As and Mn determined. The total sorption capacity of the resin was 37 mg g⁻¹ for Ni(II), 35 mg g⁻¹ for Cu(II), 29 mg g⁻¹ for Fe(III) and 23 mg g⁻¹ for Pb(II). The optimum pH for the removal of metal ions was 3-5 for Ni(II), 5 for Cu(II), 4 for Fe(III) and 4-5 for Pb(II). High sorption capacity was observed when compared with other conventional chelating polymers. The sorption kinetics was fairly rapid, as apparent from the loading half time t_1/2 values, indicating a better accessibility of the chelating sites.     

New sorbents and indicator powders for preconcentration and determination of trace metals in liquid samples

Two approaches to immobilize complex-forming analytical reagents (PAN, PAR, Xylenol orange, Brombenzothiazo, Crystal violet, Cadion, and Sulfochlorophenolazorhodanine) for the preparation of new sorbents and indicator powders are suggested: on-line coating of reversed-phase silica gel by reagents or doping of porous sol-gel silica with reagents. The retention of Ag, Cd, Cu(II), Co(II), Fe(III), Mn(II), Ni, Pb, and Zn on the sorbents developed was investigated. Quantitative sorption and desorption conditions were optimized. Procedures for the determination of Cd, Cu(II), Fe(III), Pb, and Zn with flame atomic absorption, spectrophotometric, and diffusion scattering spectrometric detection were elaborated. Detection limits for Cd, Cu(II), Fe(III), Pb, and Zn were 3 μg/L, 6 μg/L, 5 μg/L, 40 μg/L, and 1 μg/L, respectively. The procedures were used for the analysis of various real samples, e.g., natural and waste waters, and food.     

Using silica modified by Tiron for metal preconcentration and determination in natural waters by inductively coupled plasma atomic emission spectrometry

A new adsorbent is synthesized on the basis of silica consecutively modified by polyhexamethylene guanidine and 4,5-dihydroxy-1,3-benzenedisulfonic acid (Tiron) for the group preconcentration of Fe(III), Al(III), Cu(II), Pb(II), Zn(II), and Mn(II) followed by determination by inductively coupled plasma atomic emission spectrometry. The adsorbent in the batch mode quantitatively (recovery 98?99%) extracts Fe(III), Al(III) and Cu(II) ions at pH 4.0 and Fe(III), Al(III), Cu(II), Pb(II), Zn(II), and Mn(II) ions at pH 7.0; the time of attainment of an adsorption equilibrium does not exceed 10 min. Consecutive preconcentration at pH 4.0 and 7.0 in the batch and dynamic modes ensures the quantitative separation of Fe(III), Al(III), and Cu(II) from Pb(II), Zn(II), and Mn(II) and their separate determination. The quantitative desorption of metals was attained with 0.5?1.0 M HNO₃ (5 or 10 mL). In preconcentration from 200 mL of solution with 5 mL of a desorbing solution, the preconcentration coefficient was equal to 40. The developed procedure was used for the determination of metal ions in river waters of Krasnoyarsk Krai. The results obtained were verified by the added?found method.     

New sorbents and indicator powders for preconcentration and determination of trace metals in liquid samples

Two approaches to immobilize complex-forming analytical reagents (PAN, PAR, Xylenol orange, Brombenzothiazo, Crystal violet, Cadion, and Sulfochlorophenolazorhodanine) for the preparation of new sorbents and indicator powders are suggested: on-line coating of reversed-phase silica gel by reagents or doping of porous sol-gel silica with reagents. The retention of Ag, Cd, Cu(II), Co(II), Fe(III), Mn(II), Ni, Pb, and Zn on the sorbents developed was investigated. Quantitative sorption and desorption conditions were optimized. Procedures for the determination of Cd, Cu(II), Fe(III), Pb, and Zn with flame atomic absorption, spectrophotometric, and diffusion scattering spectrometric detection were elaborated. Detection limits for Cd, Cu(II), Fe(III), Pb, and Zn were 3 μg/L, 6 μg/L, 5 μg/L, 40 μg/L, and 1 μg/L, respectively. The procedures were used for the analysis of various real samples, e.g., natural and waste waters, and food. Received: 17 July 1997 / Revised: 20 January 1998 / Accepted: 5 February 1998     

2-{[1-(3,4-Dihydroxyphenyl)methylidene]amino}benzoic acid immobilized Amberlite XAD-16 as metal extractant

2-{[1-(3,4-Dihydroxyphenyl)methylidene]amino}benzoic acid (DMABA) was loaded on Amberlite XAD-16 (AXAD-16) via azo linker and the resulting resin AXAD-16-DMABA explored for enrichment of Zn(II), Mn(II), Ni(II), Pb(II), Cd(II), Cu(II), Fe(III) and Co(II). The optimum pH values for extraction are 6.5-7.0, 5.0-6.0, 5.5-7.5, 5.0-6.5, 6.5-8.0, 5.5-7.0, 4.0-5.0 and 6.0-7.0, respectively. The sorption capacity was found between 97 and 515 μmol g⁻¹ and the preconcentration factors from 100 to 450. Tolerance limits for foreign species are reported. The kinetics of sorption is fast as t_1/2 is ≤5 min. The chelating resin can be reused for 50 cycles of sorption-desorption without any significant change (<1.5%) in the sorption capacity. The limit of detection values (blank +3 s) are 1.12, 1.38, 1.76, 0.67, 0.77, 2.52, 5.92 and 1.08 μg L⁻¹ for Zn(II), Mn(II), Ni(II), Pb(II), Cd(II), Cu(II), Fe(III) and Co(II), respectively. The enrichment on AXAD-16-DMABA coupled with monitoring by flame atomic absorption spectrometry (FAAS) is used to determine all the metal ion ions in river and synthetic water samples, Co in vitamin tablets and Zn in milk samples.