Solid phase extraction and diffusive gradients in thin films techniques for determination of total and labile concentrations of Cd(II), Cu(II), Ni(II) and Pb(II) in Black Sea water

Total dissolved and labile concentrations of Cd(II), Cu(II), Ni(II) and Pb(II) were determined at six locations of the Bourgas Gulf of the Bulgarian Black Sea coast. Solid phase extraction procedure based on monodisperse, submicrometer silica spheres modified with 3-aminopropyltrimethoxysilane followed by the electrothermal atomic absorption spectrometry (ETAAS) was developed and applied to quantify the total dissolved metal concentrations in sea water. Quantitative sorption of Cd, Cu, Ni and Pb was achieved in the pH range 7.5–8, for 30?min, adsorbed elements were easily eluted with 2?mL 2?mol?L^?1 HNO₃. Since the optimal pH for quantitative sorption coincides with typical pH of Black Sea water (7.9–8.2), on-site pre-concentration of the analytes without any additional treatment was possible. Detection limits achieved for total dissolved metal quantification were: Cd 0.002?µg?L^?1, Cu 0.005?µg?L^?1, Ni 0.03?µg?L^?1, Pb 0.02?µg?L^?1 and relative standard deviations varied from 5–13% for all studied elements (for typical Cd, Cu, Ni and Pb concentrations in Black Sea water). Open pore diffusive gradients in thin films (DGT) technique was employed for in-situ sampling and pre-concentration of the sea water and in combination with ETAAS was used to determine the proportion of dynamic (mobile and kinetically labile) species of Cd(II), Cu(II), Ni(II) and Pb(II) in the sea water. Obtained results showed strong complexation for Cu and Pb with sea water dissolved organic matter. The ratios between DGT-labile and total dissolved concentrations found for Cu(II) and Pb(II) were in the range 0.2–0.4. For Cd and Ni, these ratios varied from 0.6 to 0.8, suggesting higher degree of free and kinetically labile species of these metals in sea water.     

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.     

AgNP/Bi/Nafion‐modified Disposable Electrodes for Sensitive Zn(II), Cd(II), and Pb(II) Detection in Aerosol Samples

A new method for modifying electrodes with Ag nanoparticles (AgNPs) using electrospray deposition for sensitive, selective detection of Zn(II), Cd(II), and Pb(II) in aerosol samples when combined with Bismuth and Nafion coating and square‐wave anodic stripping voltammetry (SWASV) is reported. Carbon stencil‐printed electrodes (CSPEs) fabricated on a polyethylene transparency (PET) sheet were produced for an inexpensive, simple to fabricate, disposable sensor that can be used with the microliter sample volumes for analysis. Sensor performance was improved by modifying the electrode surface with electrospray‐deposited AgNPs. The use of electrospray deposition resulted in more uniform particle dispersion across the electrode surface when compared to drop‐casting. Using AgNP‐modified electrodes combined with Bi and Nafion, experimental detection limits (LODs) of 5.0, 0.5, and 0.1 μg L⁻¹ for Zn(II), Cd(II), and Pb(II), respectively, were achieved. The linear working ranges were 5.0–400.0 μg L⁻¹, 0.5–400.0 μg L⁻¹, and 0.1–500.0 μg L⁻¹ for Zn(II), Cd(II), and Pb(II), respectively. Interference studies showed Cu(II) was the only metal that interfered with this assay but inference could be eliminated with the addition of ferricyanide directly to the sample solution. This electrochemical sensor was applied for the simultaneous determination of Zn(II), Cd(II), and Pb(II) within source particulate matter (PM) samples collected on filters using an aerosol test chamber.     

Determination of trace Pb(Ⅱ), Cd(Ⅱ) and Zn(Ⅱ) using differential pulse stripping voltammetry without Hg modification

In this work,we reported a simultaneous determination approach for Pb(II),Cd(II)and Zn(II)atμg L 1concentration levels using differential pulse stripping voltammetry on a bismuth film electrode(BiFE).The BiFE could be prepared in situ when the sample solution contained a suitable amount of Bi(NO)3,and its analytical performance was evaluated for the simultaneous determination of Pb(II),Cd(II)and Zn(II)in solutions.The determination limits were found to be 0.19μg L 1for Zn(II),and0.28μg L 1for Pb(II)and Cd(II),with a preconcentration time of 300 s.The BiFE approach was successfully applied to determine Pb(II),Cd(II)and Zn(II)in tea leaf and infusion samples,and the results were in agreement with those obtained using an atomic absorption spectrometry approach.Without Hg usage,the in situ preparation for BiFE supplied a green and acceptability sensitive method for the determination of the heavy metal ions.     

Anodic Stripping Voltammetry Combined with Sequential Injection Analysis for Measurements of Trace Metal Ions with Bismuth‐ and Antimony Film Electrodes under Comparable Conditions

Anodic stripping voltammetry combined with sequential injection analysis (ASV‐SIA) was selected to examine the use of bismuth‐ and antimony‐film plated glassy carbon electrodes under comparable conditions for the determination of Pb(II) and Cd(II) ions. Of interest were the conditions for film deposition, as well as the composition of sample/carrier solutions, including concentrations of Sb(III) or Bi(III) and HCl. Then, by the optimized procedure, one could determine Pb(II), Cd(II), and Zn(II) ions at the low µg L^?1 level and ASV‐SIA configuration with both electrodes tested on analysis of a water sample.     

Simultaneous Determination of Cd(II), Cu(II), Pb(II) and Zn(II) in Human Plasma by Potentiometric Stripping Analysis

In this paper, Potentiometric Stripping Analysis (PSA) was simultaneously used to determine the concentrations of trace metals (Zn, Cd, Pb and Cu) in human plasma. The metal ions were concentrated as their amalgams on the glassy carbon surface of a working electrode that was previously coated with a thin mercury film and then stripped by a suitable oxidant. The selection of the experimental conditions was made by using the experimental‐designed methodology. The optimum conditions of the method includes a 0.2 M HAc‐NaAc buffer mixture (pH 4.5) as supporting electrolyte, and an electrolysis potential of‐1220 mV. The limits of detection (LOD) were obtained 1 μg L^?1 for Zn(II) and Pb(II), 0.5 μg L^?1 for Cu(II) and 2 μg L^?1 for Cd(II) in the studied medium. The good recoveries were obtained for the analysis in human plasma. The method was applied to blood samples, using the method of standard additions and the results were compared with Inductively Coupled Plasma‐Atomic Emission Spectrometry (ICP‐AES) as reference method. Furthermore, a simple digestion protocol of samples is investigated compared to the conventional digestion method.     

Anodic Stripping Voltammetry Determination of Pb(II) and Cd(II) at a Bismuth/Poly(aniline) Film Electrode

Abstract

A novel voltammetric method—anodic—using a bismuth/poly(aniline) film electrode has been developed for simultaneous measurement of Pb(II) and Cd(II) at low µg L^?1 concentration levels by stripping voltammetry. The results confirmed that the bismuth/poly(aniline) film electrode offered high‐quality stripping performance compared with the bismuth film electrode. Well‐defined sharp stripping peaks were observed for Pb(II) and Cd(II), along with an extremely low baseline. The detection limits of Pb(II) and Cd(II) are 1.03 µg L^?1 and 1.48 µg L^?1, respectively. The bismuth/poly (aniline) electrode has been applied to the determination of Pb(II) in tap water samples with satisfactory results.     

Simultaneous Voltammetric Determination of Zn(II), Pb(II), Cu(II), and Hg(II) in Ethanol Fuel Using an Organofunctionalized Modified Graphite‐Polyurethane Composite Disposable Screen‐Printed Device

A disposable screen‐printed device containing working, auxiliary, and reference electrodes is proposed for the simultaneous voltammetric determination of Zn(II), Pb(II), Cu(II), and Hg(II) in ethanol fuel. The working electrode was printed using an ink modified with 2‐benzothiazole‐2‐thiol organofunctionalized SBA‐15 silica, in order to increase sensitivity. The performance of this electrode was compared with that of bare and SBA‐15‐modified electrodes. After optimizing the experimental parameters, the device was applied in determination of the analytes in commercial ethanol fuel samples, using 0.10 mol L^?1 KCl/ethanol ratios of 30 : 70 (v/v), with [H⁺]=10^?5 mol L^?1. After 5 min of preconcentration at ? 1.3 V (vs. pseudo‐Ag/AgCl), four well‐resolved signals were obtained, enabling simultaneous determination of the four analytes using a differential pulse anodic stripping voltammetry (DPASV) procedure. The limits of detection were 0.30, 0.065, 0.030, and 0.046 µmol L^?1 for Zn(II), Pb(II), Cu(II), and Hg(II), respectively. The results of these analyses were in agreement with those obtained using graphite furnace atomic absorption spectroscopy (GFAAS) for Pb(II), Cu(II), and Hg(II), and high‐resolution continuum source flame atomic absorption spectrometry (HR‐CS‐FAAS) for Zn²⁺, at a 95 % confidence level. Analytes originally present in the samples could be detected, and the interference of some cations and anions was evaluated.     

Simultaneous Detection of Copper,Lead and Zinc on Tin Film/Gold Nanoparticles/Gold Microelectrode by Square Wave Stripping Voltammetry

In this work, three heavy metals (Cu(II), Pb(II) and Zn(II)) in wide potential window were simultaneously detected on tin film/gold nanoparticles/gold microelectrode (Sn/GNPs/gold microelectrode) by the method of square wave stripping voltammetry. The Sn/GNPs/gold microelectrode was fabricated by in situ plating of a Sn film on a gold nanoparticles (GNPs) modified gold microelectrode. The influence of hydrogen overflow on stripping of Zn(II) on the gold microelectrode was reduced by modification of GNPs, which made the stripping potential of target metals shift positively. The interference of sulfhydryl groups was reduced and the selectivity of the microelectrode was improved due to the addition of Sn in the detection solution. After accumulation at ?1.4 V for 300 s in acetate buffer solution (0.1 mol L^?1, pH 4.5), the Sn/GNPs/gold microelectrode revealed a good linear behavior in the examined concentration ranges from 5 to 500 µg L^?1 for Cu(II) and Pb(II), and from 10 to 500 µg L^?1 for Zn(II), with a limit of detection of 2 µg L^?1 for Cu(II), 3 µg L^?1 for Pb(II) and 5 µg L^?1 for Zn(II) (S/N=3). When compared with a Sb/GNPs/gold microelectrode and a Bi/GNPs/gold microelectrode, the Sn/GNPs/gold microelectrode showed the best stripping performance to Cu(II), Pb(II) and Zn(II). As a new type of environment‐friendly electrode, the Sn/GNPs/gold microelectrode has potential applications for detection of heavy metals.     

Evaluation of Bismuth Modified Carbon Thread Electrode for Simultaneous and Highly Sensitive Cd (II) and Pb (II) Determination

Bismuth film modified and chemically activated carbon micro‐thread electrodes were investigated for the simultaneous determination of Cd(II) and Pb(II) using square wave anodic stripping voltammetry. The carbon thread electrode was characterised using both surface and electrochemical techniques. Electrochemical impedance spectroscopy (EIS) studies demonstrated that the H₂SO₄/IPA‐treated carbon thread electrode showed a much improved resistance response (R_ct=23 Ω) compared to the IPA‐untreated carbon thread (R_ct=8317 Ω). Furthermore, parameters such as the effect of deposition potential, deposition time and Bi(III) concentration were explored using square wave voltammetry. Detection limits (S/N=3) for Cd(II) and Pb(II) were found to be 1.08 µg L^?1 and 0.87 µg L^?1, respectively and response was found to be linear over the range 5–110 µg L^?1. The proposed Bi/IPA‐treated carbon thread electrode exhibited a high selectivity towards Cd(II) and Pb(II) even in the presence of a range of heavy metals and is capable of repetitive and reproducible measurements, being attributed to the high surface area, geometry and electrode treatment characteristics. The proposed metal ion sensor was employed to determine cadmium and lead in river water samples and % RSD was found to be 5.46 % and 5.93 % for Cd(II) and Pb(II) respectively (n=3). Such facile sensing components favour the development of cost effective portable devices for environmental sample analysis and electrochemical applications.     

Preparation, characterization, and application of a new thiol-functionalized ionic liquid for highly selective extraction of Cd(II)

A highly selective thiol-functionalized ionic liquid (thiol-FIL) was synthesized and characterized by FT-IR and ESI mass spectroscopy. The capability of thiol-FIL to extract Cd(II), Ni(II), Cr(III) and Pb(II) was evaluated. It is found that thiol-FIL possesses high selectivity for Cd(II), and this has led to a method for determination of Cd(II) by flame atomic absorption spectrometry that is free of interferences by up to a 1,000-fold excess of Na(I), Mg(II), Ca(II), Mn(II), Fe(III), Al(III), Cu(II), Zn(II), Ni(II), Cr(III), Co(II), As(III), Pb(II), and Hg(II). With extraction equilibrium time of 1 min, a good linearity (r = 0.9998) and a detection limit of 0.39 μg?L^?1 were obtained. The precision (RSD) for 11 replicate measurements of 10 μg?L^?1 Cd was 1.6%. The method was validated using certified reference materials. The recoveries of cadmium in spiked real samples ranged from 97% to 102%.     

A novel method for the simultaneous determination of Pb (II), Cd (II) and Zn (II) in environmental water samples

A novel UV-VIS spectrophotometric method was developed in this study by using solid phase extraction procedure for the simultaneous preconcentration, separation and determination of trace levels of Pb (II), Cd (II) and Zn (II) ions in various water samples by using Amberlite N,N-bis(salicylidene)cyclohexanediamine (SCHD) resin. This study presents the results of experimental procedures carried out like the adsorption of analytes to the resin, influences of some analytical parameters that effect the recovery such as pH, sample volume, sample flow rate, eluent type and concentration, eluent volume, eluent flow rate and the effects of alkaline metals, earth alkaline metals and some other transition metals. The analytes in the samples with the adjusted pH range of 4–7 were adsorbed on XAD-4-SCHD resin and eluted by using 1.0 mol L^?1 nitric acid. The amounts of ions were determined by using UV-VIS spectrometer. The limits of detection were 0.03, 0.07 and 0.05 µg mL^?1 for Pb (II), Cd (II) and Zn (II), respectively. The accuracy of the method was assured by the analysis of the certified standard water sample NW-TMDA-70.2 and the observed recoveries were above 93%. Different environmental water samples that contain trace amounts of Pb (II), Cd (II) and Zn (II) were analysed by using the method developed in this study. Same samples were also analysed by ICP-MS for comparison and almost the similar results were observed. The method developed in this study was successfully applied to the various environmental water samples to determine the trace levels of Pb (II), Cd (II) and Zn (II) ions.     

Voltammetric Quantification of Zn and Cu,Together with Hg and Pb,Based on a Gold Microwire Electrode,in a Wider Spectrum of Surface Waters

The simultaneous determination of Zn and Cu by anodic stripping voltammetry (ASV) is prone to errors due to the formation of Cu‐Zn intermetallic compounds. The main aim of this work was to study the possibility of simultaneous determination of Zn and Cu, together with Hg and Pb, using a mercury‐free solid gold microwire electrode. The multi‐element detection was carried out by differential pulse anodic stripping voltammetry (DPASV), in a chloride medium (0.5 M NaCl) under moderate acid conditions (HCl 1.0 mM) in the presence of oxygen, where the gold microwire electrode was used as stationary or vibrating working electrode during the deposition step. Under these conditions, no formation of Cu‐Zn intermetallic compounds were found for concentrations usually determined in surface waters. In addition, quantification of Zn and Cu, together with Hg and Pb, can be performed in a wide range of concentrations (about two orders of magnitude) using the same sample, in a very short period of time. The detection limits for Cu, Hg, Pb and Zn, using a vibrating electrode and 30 s of deposition time, were 0.2 µg L^?1 for Hg, 0.3 µg L^?1 for Pb and 0.4 µg L^?1 for Zn and Cu, respectively. The proposed DPASV methods were successfully applied to the determination of Cu, Hg, Pb, and Zn in a certified reference fresh water, river, tap and coastal sea waters. These results proved the applicability and versatility of the proposed methods for the analysis of different water matrices and showed that a gold microwire electrode is a suitable choice to determine simultaneously Zn and Cu.     

Sequential injection anodic stripping voltammetry with monosegmented flow and in-line UV digestion for determination of Zn(II), Cd(II), Pb(II) and Cu(II) in water samples

A cost-effective sequential injection system incorporating with an in-line UV digestion for breakdown of organic matter prior to voltammetric determination of Zn(II), Cd(II), Pb(II) and Cu(II) by anodic stripping voltammetry (ASV) on a hanging mercury drop electrode (HMDE) of a small scale voltammetric cell was developed. A low-cost small scale voltammetric cell was fabricated from disposable pipet tip and microcentrifuge tube with volume of about 3 mL for conveniently incorporated with the SI system. A home-made UV digestion unit was fabricated employing a small size and low wattage UV lamps and flow reactor made from PTFE tubing coiled around the UV lamp. An in-line single standard calibration or a standard addition procedure was developed employing a monosegmented flow technique. Performance of the proposed system was tested for in-line digestion of model water samples containing metal ions and some organic ligands such as strong organic ligand (EDTA) or intermediate organic ligand (humic acid). The wet acid digestion method (USEPA 3010a) was used as a standard digestion method for comparison. Under the optimum conditions, with deposition time of 180 s, linear calibration graphs in range of 10-300 μg L⁻¹ Zn(II), 5-200 μg L⁻¹ Cd(II), 10-200 μg L⁻¹ Pb(II), 20-400 μg L⁻¹ Cu(II) were obtained with detection limit of 3.6, 0.1, 0.7 and 4.3 μg L⁻¹, respectively. Relative standard deviation were 4.2, 2.6, 3.1 and 4.7% for seven replicate analyses of 27 μg L⁻¹ Zn(II), 13 μg L⁻¹ Cd(II), 13 μg L⁻¹ Pb(II) and 27 μg L⁻¹ Cu(II), respectively. The system was validated by certified reference material of trace metals in natural water (SRM 1640 NIST). The developed system was successfully applied for speciation of Cd(II) Pb(II) and Cu(II) in ground water samples collected from nearby zinc mining area.     

Antimony film screen-printed carbon electrode for stripping analysis of Cd(II), Pb(II), and Cu(II) in natural samples

An in-situ antimony film screen-printed carbon electrode (in-situ SbSPCE) was successfully used for the determination of Cu(II) simultaneously with Cd(II) and Pb(II) ions, by means of differential pulse anodic stripping voltammetry (DPASV), in a certified reference groundwater sample with a very high reproducibility and good trueness. This electrode is proposed as a valuable alternative to in-situ bismuth film electrodes, since no competition between the electrodeposited copper and antimony for surface sites was noticed. In-situ SbSPCE was microscopically characterized and experimental parameters such as deposition potential, accumulation time and pH were optimized. The best voltammetric response for the simultaneous determination of Cd(II), Pb(II) and Cu(II) ions was achieved when deposition potential was −1.2 V, accumulation time 120 s and pH 4.5. The detection and quantification limits at levels of μg L⁻¹ suggest that the in-situ SbSPCE could be fully suitable for the determination of Cd(II), Pb(II) and Cu(II) ions in natural samples.     

Novel Imprinted Polymer for the Preconcentration of Cadmium with Determination by Inductively Coupled Plasma Mass Spectrometry

A novel Cd(II)-imprinted polymer was prepared with chemical immobilization using N-methacryloyl-L-Histidine as a vinylated chelating agent for online solid-phase extraction of Cd(II) for determination by inductively coupled plasma mass spectrometry. The Cd(II)–monomer complex was synthesized and copolymerized through bulk polymerization method in the presence of ethyleneglycoldimethacrylate cross-linker. The resulting polymer was leached with 1.0?mol?L^?1 HNO₃ to generate the cavities in the polymer for Cd(II) ions. The experimental conditions, including load pH, solution flow rate, and eluent concentration for effective sorption of Cd(II), were optimized using a minicolumn of the imprinted polymer. A volume of 5.0?mL sample 5?µg?L^?1 Cd(II) solution at pH 6.5 was loaded on the column at 2.0?mL?min^?1 using a sequential injection system followed by elution with 1.0?mL of 0.75?mol?L^?1 HNO₃. The relative selectivity coefficients of the imprinted polymer for Cd(II) were 38.5, 3.5, 3.0, 2.5, and 6.0 in the presence of Cu(II), Ni(II), Zn(II), Co(II), and Pb(II), respectively. Computational calculations revealed that the selectivity of the imprinted polymer was mediated by the stability of Cd(II)–N-methacryloyl-L-Histidine complex which was more stable than commonly used monomers including 4-vinyl pyridine, methacrylic acid, and vinylimidazole. The detection limit and relative standard deviation were 0.004?µg?L^?1 and 3.2%, respectively. The method was validated by the analysis of seawater certified reference material (CASS-4) and successfully used for the determination of Cd(II) in coastal seawater and estuarine water.     

Activated carbon cloth filled pipette tip for solid phase extraction of nickel(II), lead(II), cadmium(II), copper(II) and cobalt(II) as 1,3,4-thiadiazole-2,5-dithiol chelates for ultra-trace detection by FAAS

A solid phase extraction method is established for preconcentration of nickel, lead, cadmium, copper and cobalt using pipette tip solid phase extraction. The presented process was dependent on chelation of analytes with 1,3,4-thiadiazole-2,5-dithiol, then allowing the solution to flow through an activated carbon cloth packed pipette tip. The adsorbed metal chelates on the surface of activated carbon cloth were eluted by 5 mL of 3 M HNO₃. The concentrations of nickel, lead, cadmium, copper and cobalt were detected using a flame atomic absorption spectrometer (FAAS). The pipette tip solid phase extraction exhibit a preconcentration factor of 120. The limit of detection values were 2.7, 1.7, 1.3, 2.0 and 2.9 µg L^?1 for Ni(II), Pb(II), Cd(II), Cu(II) and Co(II), respectively. Validation of the method was checked by the analysis of TMDA-53.3 and TMDA-64.2 certified reference materials. The method was successfully applied for water and fertiliser samples.     

Selective back-extraction and preconcentration of zinc(II) from metal-1,3,5-triketone extracts prior to its determination by flame atomic absorption spectrometry

A simple back-extraction method was developed for the separation and preconcentration of trace levels of zinc from different matrices. Ethyl-2-(4-methoxybenzoyl)-3-(4-methoxyphenyl)-3-oxopropanoylcarbamate (EMPC) was used as a new complexing agent for the extraction of zinc(II) from the aqueous sample phase to the methyl isobutyl ketone (MIBK) phase as Zn(EMPC)₂ complexes. The Zn(II) can be selectively stripped with 1?mL of 0.5?mol?L^?1 HCl from Mⁿ⁺(EMPC)_n complexes [Ag(I), Al(III), Cd(II), Cr(III), Cu(II), Fe(II), Fe(III), Mn(II), Ni(II), Pb(II) and Pd(II)] which dissolved in MIBK phase. Some experimental parameters, which are important for the whole extraction process, including pH, sample volume, shaking time, amount of the EMPC reagent, amount of MIBK, ionic strength, and type of back-extractant were investigated. The recovery for Zn(II) was greater than 95%. The detection limit of the method was found to be 0.2?µg?L ^{? 1} and the relative standard deviation as 6.4%. The concentrations of Zn(II) in the certified reference materials (LGC6019 river water and NIST-1547 peach leaves) by the presented method were in good agreement with the certified values. The proposed method was succesfully applied to the determination of zinc in some natural waters, rice, hair, soil, and tea samples.     

Kinetics study of selective removal of lead(II) in an aqueous solution containing lead(II), copper(II) and cadmium(II) across bulk liquid membrane

Transport of Pb(II) ion from equimolar aqueous solutions of Pb(II), Cu(II) and Cd(II) as well as from aqueous solutions containing only Pb(II) source phase (C_metal = 1.0 × 10^?4 mol L^?1) through bulk liquid membranes containing crown ether and oleic acid as carrier has been investigated. The initial fluxes of transported metal ions depend on the hydrophile–lipophile balance (HLB) and molar volumes (Vx) of crown ethers. The initial fluxes of Pb(II), Cu(II), and Cd(II) decrease with increase of HLB value for azacrown ether, i.e., tetraaza-14-crown-4 (A₄14C4), L1 > benzo-15-crown-5 (B15C5), L2 > 4′-Aminobenzo-15C5, L3 > nitrobenzo-15-crown-5 (NB15C5), L4. The selectivity of the metal ions showed the following separation factors (SF): SF_Pb–Cu = 2.15, SF_Cu–Cd = 2.10, SF_Pb–Cd = 4.52. The highest transport recovery for Pb(II) was observed for L1 (99.3 %).     

Silica gel surface modified with sulfanilamide for selective solid-phase extraction of Cu(II), Zn(II) and Ni(II)

A new chelating matrix has been prepared by immobilising sulfanilamide (SA) on silica gel (SG) surface modified with 3-chloropropyltrimethoxysilane as a sorbent for the solid-phase extraction (SPE) Cu(II), Zn(II) and Ni(II). The determination of metal ions in aqueous solutions was carried out by inductively coupled plasma optical emission spectrometry (ICP-OES). Experimental conditions for effective sorption of trace levels of Cu(II), Zn(II) and Ni(II) were optimised with respect to different experimental parameters using the batch and column procedures. The presence of common coexisting ions does not affect the sorption capacities. The maximum sorption capacity of the sorbent at optimum conditions was found to be 34.91, 19.07 and 23.62 mg g^?1 for Cu(II), Zn(II) and Ni(II), respectively. The detection limit of the method defined by IUPAC was found to be 1.60, 0.50 and 0.61 µg L^?1 for Cu(II), Zn(II) and Ni(II), respectively. The relative standard deviation (RSD) of the method under optimum conditions was 4.0% (n = 8). The method was applied to the recovery of Cu(II), Zn(II) and Ni(II) from the certified reference material (GBW 08301, river sediment) and to the simultaneous determination of these cations in different water samples with satisfactory results.