Preconcentration and Determination of Copper（Ⅱ） Using Octadecyl Silica Membrane Disks Modified by 1,5-Diphenylcarhazide and Flame Atomic Absorption Spectrometry

A simple and reproducible method for the rapid extraction and determination of trace amounts of copper（Ⅱ） ions using octadecyl-bonded silica membrane disks modified by 1,5-diphenylcarbazide （DPC） and atomic absorption spectrometry was presented, which was based on complex formation on the surface of the ENVI-18 DISK^TM disks followed by stripping of the retained species by minimum amounts of appropriate organic solvents. The elution was efficient and quantitative. The effect of potential interfering ions, pH, ligand amount, stripping solvent, and sample flow rate were also investigated. Under the optimal experimental conditions, the break-through volume was found to be about 1000 mL providing a preconcentration factor of 400. The maximum capacity of the disks was found to be （255±5） lag for Cu^2＋, and the limit of detection of the proposed method was 5 ng per 1000 mL. The method was applied to the extraction and recovery of copper in different water samples.     

Preconcentration and Determination of Chromium Species Using Octadecyl Silica Membrane Disks and Flame Atomic Absorption Spectrometry

A novel and selective method for the fast determination of trace amounts of chromium species in water samples has been developed. The procedure is based on the selective formation of chromium diethyldithiocarbamate complexes at different pH in the presence of Mn(II) as an enhancement agent of chromium signals followed by elution with organic eluents and determination by atomic flame absorption spectrometry. The maximum capacity of the employed disks was found to be (396±3) µg and (376±2) µg for Cr(III) and Cr(VI), respectively. The detection limit of the proposed method is 49 and 43 ng·L^?1 for Cr(III) and Cr(VI), respectively. The proposed method was successfully applied for determination of chromium species Cr(III) and Cr(VI) in different water samples.     

Adsorptive Cathodic Stripping Voltammetric Method for Determination of Gallium Using an In Situ Plated Lead Film Electrode

The in situ plated lead film electrode was proposed for the first time for adsorptive stripping voltammetric determination of gallium in water samples. The method was based on simultaneous lead film formation and Ga(III)‐cupferron complex preconcentration at ?0.7 V and its cathodic stripping during the potential scan. The composition of the supporting electrolyte, cupferron concentration, conditions of lead film formation, potential and time of accumulation were studied in detail. Under optimum conditions the limit of detection was 3.8×10^?9 mol L^?1. The proposed procedure was validated in the course of Ga(III) determination in waste water certified reference materials.     

Simultaneous Determination of Nickel and Cadmium by Adsorptive Stripping Voltammetry

A sensitive and fast method for the simultaneous determination of trace amounts of nickel and cadmium in real samples has been described using differential pulse adsorptive stripping voltammetry (DPASV) by adsorptive accumulation of the N,N′‐bis(salicylaldehydo)4‐carboxyphenylenediamine (BSCPDA)–complex on the hanging mercury drop electrode (HMDE). As supporting electrolyte 0.02 mol L^?1 ammonia buffers containing ligand has been used. Optimal analytical conditions were found to be: BSCPDA concentration of 42 μM, pH 9.6 and adsorption potential at ?50 mV versus Ag/AgCl. With an accumulation time of 20 s, the peaks current are proportional to the concentration of nickel and cadmium over the 1–180, and 0.5–200 ng mL^?1 with detection limits of 0.06 and 0.03 ng mL^?1 respectively. The sensitivity of method for determination of nickel and cadmium were obtained 0.54 and 0.98 nA mL ng^?1, respectively. The procedure was applied to simultaneous determination of nickel and cadmium in some real and synthetic artificial samples with satisfactory results.     

Determination of Some Heavy Metal Ions with a Carbon Paste Electrode Modified by Poly(glycidylmethacrylate‐methylmethacrylate‐divinylbenzene) Microspheres Functionalized by 2‐Aminothiazole

A carbon paste electrode modified with 2‐aminothiazole functionalized poly(glycidylmethacrylate‐methylmethacrylate‐divinylbenzene) microspheres was used for trace determination of mercury, copper and lead ions. After the open‐circuit accumulation of the heavy metal ions onto the electrode, the sensitive anodic stripping peaks were obtained by square wave anodic stripping voltammetry (SWASV)). Many parameters such as the composition of the paste, pH, preconcentration time, effective potential scan rate and stirring rate influence the response of the measurement. The procedures were optimized for most sensitive and reliable determinations of the desired species. For a 10‐min preconcentration time in synthetic solutions at optimum instrumental and experimental conditions, the detection limit (LOD) was 12.3, 2.8 and 4.5 μg L^?1 for mercury, copper and lead, respectively. The limits of detection may be enhanced by increasing the preconcentration time. For example, LOD of mercury and copper was 4.9 and 1.0 μg L^?1 for fifteen minutes preconcentration time. The sensitivity may also considered to be increased by using a more suitable electrode composition targeting the more conductive electrode with lesser amount of modified polymer for sub‐μg L^?1 levels of heavy metal ions. The optimized method was successfully applied to the determination of copper in tap water and waste water samples by means of standard addition procedure. The copper content found was comparable with the certified concentration of the waste water sample. The calibration plots for mercury and lead spiked real samples were also drawn.     

Solid phase extraction of trace amount of Cu(II) using functionalized-graphene

A novel and selective method for the fast determination of trace amounts of Cu(II) ions in water samples has been developed. The first organic-solution-processable functionalized-graphene (SPF-Graphene) hybrid material with porphyrins, porphyrin-graphene nanohybrid, 5-(4-aminophenyl)-10, 15, 20-triphenyl porphyrin and its photophysical properties including optical (TPP) and grapheme oxide molecules covalently bonded together via an amide bond (TPP-NHCO-SPFGraphene) were used as absorbent for extraction of Cu(II) ions by solid phase extraction method. The complexes were eluted with HNO₃ (2 M) 10% (vol/vol) methanol in acetone and determined the analyte by flame atomic absorption spectrometry. The procedure is based on the selective formation of Cu(II) at optimum pH by elution with organic eluents and determination by flame atomic absorption spectrometry. The method is based on complex formation on the surface of the ENVI-18 DISK? disks modified porphyrin-graphene nanohybrid, 5-(4-aminophenyl)-10,15,20-triphenyl porphyrin (TPP) and grapheme oxide molecules covalently bonded together via an amide bond (TPP-NHCO-SPFGraphene) followed by stripping of the retained species by minimum amounts of appropriate organic solvents. The elution is efficient and quantitative. The effect of potential interfering ions, pH, TPP-NHCO-SPFGraphene, amount, stripping solvent, and sample flow rate were also investigated. Under the optimal experimental conditions, the break-through volume was found to about 1000 mL providing a preconcentration factor of 600. The maximum capacity of the disks was found to be 398 ± 3 μg for Cu²⁺. The limit of detection of the proposed method is 5 ng per 1000 mL. The method was applied to the extraction and recovery of copper in different water samples.     

Trace Determination of Chromium by Square‐Wave Adsorptive Stripping Voltammetry on Bismuth Film Electrodes

This works reports the use of adsorptive stripping voltammetry (AdSV) for the trace determination of chromium on a rotating‐disk bismuth‐film electrode (BFE). During the reductive accumulation step, all the chromium species in the sample were reduced to Cr(III) which was complexed with cupferron and the complex was accumulated by adsorption on the surface of a preplated BFE. The stripping step was carried out by using a square‐wave (SW) potential‐time voltammetric signal. Electrochemical cleaning of the bismuth film was employed, enabling the same bismuth film to be used for a series of measurements in the presence of dissolved oxygen. The experimental variables as well as potential interferences were investigated and the figures of merit of the method were established. Using the selected conditions, the 3σ limit of detection for chromium was 100 ng L^?1 (for 120 s of preconcentration) and the relative standard deviation was 3.6% at the 2 μg L^?1 level (n=8). Finally, the method was applied to the determination of chromium in real samples with satisfactory results.     

Adsorptive Cathodic Stripping Voltammetric Determination of Uranium(VI) in Presence of N‐Phenylanthranilic Acid

N‐Phenylanthranilic acid was used as a complexing agent for determination of uranium(VI) by adsorptive cathodic stripping voltammetry. Under the optimal experimental conditions of the experimental parameters, the peak current was proportional to the concentration of U(VI) in the range 0.75–30 ng mL^?1 and the detection limit was 0.036 ng mL^?1. The influence of possible interferences was investigated. The method was applied for determination of uranium in waste water from uranium conversion facility and natural water samples. Application of the method for simultaneous determination of U(VI) and Cu(II) showed that these ions could be simultaneously determined in a single scan at relatively wide concentration range.     

Study on the Solid Phase Extraction of Hg(II)‐ABR Chelate with C18 Disks and its Application to the Determination of Mercury in Tobacco and Tobacco Additives

A highly sensitive, selective and rapid method for the determination of mercury based on the rapid reaction of mercury(II) with 5‐(p‐aminobenzylidene)‐rhodanine (ABR) and the solid phase extraction of the colored chelate with C₁₈ disks has been developed. In the presence of pH = 3.5 sodium acetate‐acetic acid buffer solution and Emulsifier‐OP medium, ABR reacts with mercury(II) to form a red chelate of a molar ratio 1:2 (mercury to ABR). This chelate was enriched by the solid phase extraction with C₁₈ disks and eluted the retained chelate from the disks with dimethyl formamide (DMF). The enrichment factor of 50 was achieved. In the DMF medium, the molar absorptivity of the chelate is 1.16 × 10⁵ L.mol^?1.cm^?1 at 540 nm. Beer's law is obeyed in the range of 0.01?3 μg/mL in the measured solution. The relative standard deviation for eleven replicated samples of 0.01 μg/mL level is 1.83%. This method was applied to the determination of mercury in tobacco and tobacco additives with good results.     

Determination of thiosulfate ions by the complexation of lead thiosulfate with 4-(2-pyridylazo)-resorcinol on the PANF-AV-17 solid phase

A procedure was developed for determining thiosulfate ions; the procedure involved their adsorption as a complex with lead ions at pH 4 on disks of polyacrylonitrile fiber filled with an AB-17 anion exchanger and determination by the reaction with 4-(2-pyridylazo)-resorcinol at pH 10. The analytical range was (0.2–0.8) × 10^?4; the detection limit was 2 μg/mL. The determination did not interfere with metal cations at the level of the maximum permissible concentrations for potable water, as well as 2–15-fold amounts of sulfites, sulfides, and iodides; 100–200-fold amounts of sulfates, pyrosulfates, and bromides; and 1000-fold amounts of chlorides. The developed procedure was used in the analysis of tap water by the “added-found” method (RSD < 20%).     

Ionic liquid ultrasound assisted dispersive liquid–liquid/micro-volume back extraction procedure for preconcentration and determination of ultra trace amounts of thallium in water and biological samples

A simple, highly sensitive and environment-friendly method, combined with flame atomic absorption spectroscopy (FAAS) is developed to preconcentrate and determine trace amounts of thallium in aqueous solutions. In the preconcentration step, the thallium (I) from 30?mL of an aqueous solution was extracted into 350?µL of ionic liquid, 1-hexyl-3-methylimidazolium hexa?uorophosphate [Hmim][PF₆], containing dicyclohexyl-18-crown-6 (DCH-18-crown-6) as complexing agent. Subsequently, the DCH-18-crown-6 complex was back-extracted into 300?µL of nitric acid (2?mol?L^?1) solution, and analyzed by FAAS. Several parameters in?uencing the extraction and determination of thallium, such as pH, concentration of DCH-18-crown-6, sonication and centrifugation times, sample volume, ionic liquid amounts, ionic strength, and concentration of stripping acid solution, were optimized. Under optimum conditions, the calibration graph was linear in the range of 5 to 400?ng?mL^?1, the detection limit was 0.64?ng?mL^?1 (3S_b/m, n?=?7), the enhancement factor was 98.2 and the relative standard deviation was ±1.43%. The results for preconcentration and determination of trace amount of thallium in waste water, well water, tap water, sea water, human hair and nail demonstrated the accuracy, recovery and applicability of the presented method.     

Indirect Determination of Sulfide by Extraction Flotation Spectrophotometry of Copper(II) with Ammonium Sulfate‐Ethanol‐Water System

A new extraction flotation spectrum method for indirect determination of trace amounts of sulfide by ammonium sulfate‐ethanol‐water system was developed. It showed that Cu(II) could combine with S^2? into precipitate (CuS) which was floated in the surface of ethanol and water in the presence of ammonium sulfate. The sulfide can be indirectly determined by determining the flotation yield of Cu(II). The linear range from 2.4 × 10^?8to 3.2 × 10^?6g/mL and the detect limit of 2.0 × 10^?8g/mL was achieved. The results showed the determination of S^2? was not affected by Pb(II), Zn(II), Cd(II), Fe(II), Co(II),Ni(II), Mn(II) and Cl^?, Br^?, I^?, etc. In the paper, the method was successfully applied to the determination of a trace amount of sulfide in polluted water samples with the advantages of simplicity of equipment, rapidity, low cost, etc.     

Pre-concentration of ultra trace amounts of copper,zinc, cobalt and nickel in environmental water samples using modified C18 extraction disks and determination by inductively coupled plasma–optical emission spectrometry

A highly sensitive and accurate method for pre-concentration and determination of ultra trace amounts of zinc, copper, cobalt and nickel ions in environmental water samples is proposed. The method is based on the solid phase extraction of these ions on C18-bonded silica extraction disks modified with a novel Schiff base 2,2′-[1,6-hexanediyl bis (nitriloethylidine)]bis-1-naphthol (HDN). The retained ions on the prepared solid phase was eluted with 10 mL 0.01 M nitric acid and measured by inductively coupled plasma–optical emission spectrometry. The extraction efficiency and the influence of the type and least amount of eluent for the stripping of ions from the disks, pH, flow rates of sample solution and eluent, amount of HDN, effect of other ions and breakthrough volume were evaluated. The limits of detection of the method were 0.2, 0.2, 0.8 and 0.6 µg L^?1 for zinc, copper, cobalt and nickel, respectively and an enrichment factor of 100 was obtained. The proposed method was applied for determination of zinc, copper, cobalt and nickel ions in some natural and synthetic water samples with satisfactory results.     

Solid phase extraction and flame atomic absorption spectroscopic determination of trace amounts of iron(III) using octadecyl silica membrane disks modified with 2-mercaptopyridine-1-oxide

A simple and selective method for rapid extraction and determination of trace amounts of iron(III) using octadecyl-bonded silica membrane disks modified with 2-mercaptopyridine-1-oxide and flame atomic absorption spectroscopy is presented. The factors influencing extraction efficiency were evaluated, including the nature of the counter anion, pH of the sample solution, amount of ligand, flow rate of the sample and type of stripping solution. The maximum capacity of the membrane disk, modified by 10 mg of the ligand, was found to be 926 ± 6 μg of iron(III). The breakthrough volume was greater than 2500 ml. Iron(III) was completely recovered (>99%) from water with a preconcentration factor of more than 166. The limit of detection of the proposed method was 0.63 ng ml^?1. The various cationic interferences had no effect on the recovery of iron(III) from the binary mixtures. The proposed method was applied to the determination of iron(III) from three different water samples.     

Direct Determination of Copper in Biodiesel Using Stripping Analysis

A simple, effective, and low‐cost protocol for copper determination in biodiesel, with no sample decomposition, is reported. Samples were diluted in an ethanol‐water solution (with HCl as supporting electrolyte) generating a homogeneous mixture at which copper was directly detected using stripping chronopotentiometry using a gold working‐electrode. The optimized mixture was 100 µL (0.088 g) of biodiesel, 15 mL of ethanol, and 5 mL of 0.1 mol L^?1 HCl aqueous solution. The estimated detection limit was 200 ng g^?1 (300‐s deposition time). The elimination of the sample treatment step offers the possibility of on‐site measurements in association with commercially‐available portable potentiostats.     

Electrochemical Determination of Some Organic Pollutants Using Wall‐Jet Electrode

Determination of organic pollutants in trace level in a flow stream was developed using a wall‐jet electrode system and square‐wave stripping principles. Pesticides such as endosulfan, isoproturon and carbendazim, o‐chlorophenol and a benzidine bisazo dye, direct orange 8 were chosen for this study. The optimum conditions for adsorptive square‐wave stripping voltammetry were arrived at and the peak current responses of analyte were correlated over flow rate. Calibration plots were obtained by correlating the peak currents with concentration under optimum conditions. The best determination range, 1×10^?4 to 4.0 mg/mL for endosulfan and 1×10^?4 to 1.5 mg/mL for the remaining pollutants in a flowing stream was obtained with adsorptive square‐wave stripping technique.     

Speciation Analysis of Cr(III) and Cr(VI) after Solid Phase Extraction Using Modified Magnetite Nanoparticles

A new solid phase extraction (SPE) method has been developed for the speciation of Cr(III) and Cr(VI). This method is based on the adsorption of Cr(VI) on modified alumina‐coated magnetite nanoparticles (ACMNPs). Total chromium in different samples was determined as Cr(VI) after oxidation of Cr(III) to Cr(VI) using H₂O₂. The chromium concentration has been determined by flame atomic absorption spectrometric (FAAS) technique and amount of Cr(III) was calculated by substracting the concentration of Cr(VI) from total chromium concentration. The effect of parameters such as pH, amount of adsorbent, contact time, sample volume, eluent type, H₂O₂ concentration and cetyltrimethylammonium bromide (CTAB) concentration as modifier on the quantitative recovery of Cr(VI) were investigated. Under the optimal experimental conditions, the preconcentration factor, detection limit, linear range and relative standard deviation (RSD) of Cr(VI) were 140 (for 350 mL of sample solution), 0.083 ng mL^?1, 0.1‐10.0 ng mL^?1 and 4.6% (for 5.0 ng mL^?1, n = 7), respectively. This method avoided the time‐consuming column‐passing process of loading large volume samples in traditional SPE through the rapid isolation of CTAB@ACMNPs with an adscititious magnet. The proposed method was successfully applied to the determination and speciation of chromium in different water and wastewater samples and suitable recoveries were obtained.     

Chromium(III) Potentiometric Sensor Based on Para‐Tertiary‐Butyl Calix[4]arene

A new chromium(III) PVC membrane sensor incorporating p‐tertiary‐butyl calix[4]arene as ionophore, potassium tetrakis as additive and dibutyl phthalate (DBP) as plasticizer was constructed. The electrode exhibited an excellent potentiometric response over a wide concentration range of 1.0×10^?7–1.0×10^?1 M with a Nernstian slope of 20±0.5 mV per decade. The detection limit was 5.0×10^?8 M. The electrode showed a better performance over a pH range of 3.0–8.0, and had a short response time of about <15 s.The electrode was successfully applied to potentiometric titration of Cr (III) with EDTA and for direct determination of chromium(III) in waste water.     

Simple and Highly Selective Catalytic Adsorptive Voltammetric Method for Cr(VI) Determination

A simple and highly selective and sensitive catalytic adsorptive stripping voltammetric procedure for determination of traces of Cr(VI) in the presence of a large excess of Cr(III) in environmental water samples is reported. To obtain a low detection limit the voltammetric procedure of chromium determination in the presence of DTPA and nitrate was exploited. For elimination of interference of Cr(III) ethylenediaminedisuccinic acid was used as a masking agent. At optimized conditions the calibration graph is linear from 2×10^?10 to 2×10^?8 mol L^?1 for accumulation time of 30 s. The validation of the procedure was performed by comparison of the results of analysis of river water samples with those obtained using other accepted voltammetric procedure.     

Determination of Copper at a Glassy Carbon Electrode Modified with Langmuir–Blodgett Film of p‐tert‐Butylthiacalix[4]arene

A new type of voltammetric sensor, Langmuir–Blodgett film of p‐tert‐butylthiacalix[4]arene modified glassy carbon electrode, was advanced and used for determining copper at trace levels by differential pulse stripping voltammetry. Calibration plot was found to be linear in the range of 2×10^?8 M to 5×10^?6 M; the detection limit was 2×10^?9 M. Possible recognition mechanism was also discussed. From determination of Copper in real samples (river, lake and tap water) it can be concluded that the method is rapid, sensitive in determining of copper and can be used in the analysis of natural water samples.