Determination of traces of palladium by adsorptive stripping voltammetry of the dimethylglyoxime complex

Preconcentration is achieved by adsorption of a palladium-dimethylglyoxime complex on a hanging mercury drop electrode. Optimal conditions area stirred acetate buffer solution (pH 5.15) containing 2 × 10^?4 M dimethylglyoxime and an accumulation potential of —0.20 V. The height of the stripping peak in a negative-going linear scan is linearly dependent on palladium concentration and preconcentration time (over the ranges 0–16 μg l^?1 and 0–300 s, respectively). For a 10-min preconcentration time, the detection limit is 20 ng l^?1 (2.1 × 10^?10 M). Possible interferences by other trace metals are investigated. Palladium added to seawater samples was easily quantified.     

The simultaneous determination of As,Cd, Co,Hg, Mo,and Zn in fresh water by neutron activation analysis

A radiochemical neutron activation method for the simultaneous determination of arsenic, cadmium, cobalt, mercury, molybdenum, and zinc in fresh water is described. The method is based on anion-exchange separation in hydrochloric acid media followed by simple precipitations. The determination limits, based on analysis of a 5-ml sample without preconcentration, and with a well-type NaI(Tl) detector, are as follows: As, 10^-3 μg l^-1 ; Cd, 6 × 10^-2 μg l^-1 ; Co, 4 × 10^-3 μg l^-1 ; Hg, 7 × 10^-3 μg l^-1 ; Mo, 10^-1 μg l^-1 ; Zn, 2 × 10^-1 μg l^-1. The method is adequate for the analysis of natural fresh waters.     

Quantitative goldbestimmung in filmmaterialien mittels flammenloser atomabsorption

A graphite rod electrothermal atomizer has been used for the AAS determination of traces of gold in hydrochloric and in hydrobromic acid solutions, and also after extraction into HBr-saturated methyl isobutyl ketone. Photographic film samples were decomposed first by enzyme action then by nitric acid/peroxide oxidation, and the gold was extracted into MIBK. For 10-μl aliquots of solution the 3s limits of detection were 3 × 10^?10g for aqueous solutions, 7 × 10^?10g for MIBK, and 7 × 10^?9 g/cm² for film.     

Stripping voltammetry of manganese based on chelate adsorption at the hanging mercury drop electrode

A novel electrochemical stripping approach for the trace measurement of manganese is presented. The metal chelate with erichrome black T is adsorbed on a hanging mercury drop electrode, and the subsequent reduction current of the accumulated chelate is measured by voltammetry. Adsorptive preconcentration for 5 min results in a detection limit of 6 × 10^?10 M (32 l^?1). Cyclic voltammetry is used to characterize the redox and interfacial processes. Optimal experimental conditions include a 0.02 M piperazine-N,N′-bis(2-ethanesulfonic acid) solution (pH 12) containing 1 × 10^?6 M eriochrome black T, a preconcentration potential of ?0.80 V, and a linear potential scan. The response is linear up to 2.9 × 10^?7 M, and the relative standard deviation at 1.8 × 10^?7 M is 1.5%. The effects of possible interferences from metal ions or organic surfactants are evaluated.     

Determination of trace amounts of silver with a chemically modified carbon paste electrode

A method for the determination of trace amounts of silver with a chemically modified carbon paste electrode is described. The modified electrode is prepared by simply mixing a chelating resin (a polythioether backbone and dioxymonosulphur polyethylene polyimines in the side-chain polymer) with graphite powder and Nujol oil. By immersing the electrode in a silver sample solution (pH = 6.5–7.5), silver can be adsorbed on the electrode surface and then determined by voltammetry in a separate blank solution. The response depends on the concentration of silver and the preconcentration time. For a preconcentration time of 5 min, the detection limit is about 3 × 10^?10 M and the linear range is from 5 × 10^?10 to 1 × 10^?7 M with a relative standard deviation of 4%. Many common metal ions have no or little effect on the determination of silver. The recommended procedure was applied to the determination of trace amounts of silver in waste water.     

L'electrode a Pate de Carbone Modifiee Son Utilisation en Voltammetrie par Redissolution Anodique a Impulsions Differentielles en Presence d'Un Film de Mercure

Abstract

The various problems which are associated with the use of carbon paste electrode as thin mercury film electrode (TKFE) for anodic stripping voltammetry (ASV) can be overcame in a very easy and rapid way. The procedure consists to coat the carbon paste surface by spraying a graphite based conductive solution. For example, the dispersion of colloidal graphite in a mixture of methyl polymethacrylate with butyl acetate (as solvent) gives interesting results. Such a surface is easily renewable and the electrode does not require any pretreatment procedure like cleaning or polarization cycles…, after coating. The technique offers the advantage to limit the risk of sample contamination and memory effects. After pulverisation, a hard, uniform and compact layer is formed after evaporation of the solvent excess.

The resulting electrode, electrochemically coated with mercury, exhibits a good stability as shown for the differential pulse anodic stripping voltammetry (DPASV) for cadmium ions. Replicate measurements were carried out in two different buffers at pH 8.5 and 5.0. Compared to the originally carbon paste electrode, a marked improvement of the reproducibility of the peak currents is observed. Calibration curves obtained by using the method of standard additions show a good linear relationship between cadmium ions concentration and peak current (down to 4×10^?10 M.L^?1).

After a deposition time of 10 minutes, the detection limit for cadmium is 1×10^?10 M.L^?l in both media).     

Electrothermal atomic absorption spectrometric determination of cadmium in environmental samples with niobium wire preconcentration method

A preconcentration method by adsorption of cadmium on a niobium wire was developed for the environmental waters, followed by electrothermal atomic absorption spectrometry with a tungsten tube atomizer. After the preconcentration, the niobium wire was directly inserted into the tungsten tube atomizer. In the preconcentration (adsorption) process of cadmium, the optimal immersing time was 60?s. The effects of large amounts of concomitants on the preconcentration of cadmium were evaluated. When 10³–10⁴ fold excess of matrix elements existed in aqueous solution at pH 4 and 9, the cadmium response was profoundly affected by the matrix elements. However, the cadmium absorption signal was not significantly influenced at pH 7. Therefore, pH 7 was selected for the application into the real environmental samples. Under the optimal conditions, the detection limit (3S/N) for cadmium by the niobium wire preconcentration method was 7.0?pg?mL^?1 and the relative standard deviation was 6.8%. The method with preconcentration on a niobium wire was applied to the determination of cadmium in water and proved to be sensitive, simple and convenient. Because this preconcentration method can be utilized in the in situ treatment of trace cadmium in environmental water samples, it was unnecessary to carry the water samples to the analytical work place. The technique was shown to be useful for the determination of cadmium in environmental water samples at 0.1–1?µg?L^?1 levels.     

Determination of cadmium in water samples by graphite furnace atomic absorption spectrometry after cloud point extraction

The formation of a complex with 2-(5-brom-2-pyridylazo)-5-(diethylamino)-phenol (5-Br-PADAP) and cloud point extraction have been applied to the preconcentration of cadmium followed by its determination by graphite furnace atomic absorption spectrometry (GFAAS) using octylphenoxypolyethoxyethanol (TritonX-114) as surfactant. The chemical variables affecting the separation were optimized. At pH 7.0, preconcentration of only 10 mL of sample in the presence of 0.05% TritonX-114 and 2.5 × 10⁻⁶ M 5-Br-PADAP enabled the detection of 0.04 μg/L cadmium. The enrichment factor was 21 for cadmium. The regression equation was A = 0.0439C(μg/L) + 7.2 × 10⁻³. The correlation coefficient was 0.9995. The precision for 10 replicate determinations at 10 μg/L Cd was 2.7% relative standard deviation (RSD). The proposed method has been applied to the determination of cadmium in water samples. The text was submitted by the authors in English.     

Anodic Stripping Voltammetric Determination of Mercury in Water Using a Chitosan‐Modified Carbon Paste Electrode

Abstract

This paper describes the preparation and electrochemical application of a modified carbon paste electrode with chitosan for the determination of Hg(II) ions in water using anodic stripping voltammetry. Experimental parameters, including the pH of the supporting electrolyte, time and potential of accumulation and scan rate were investigated. The best voltammetric response was observed for a paste composition of 60% (m/m) of graphite powder, 20% (m/m) of chitosan and 20% (m/m) of mineral oil, with 0.1 mol/l NaNO₃ solution at pH 6.3 as supporting electrolyte, a preconcentration potential of ?0.2 V, preconcentration time of 270 s and a scan rate of 25 mV/s. Under these optimal experimental conditions, the voltammetric signals were linearly dependent on the Hg(II) concentration in the range of 9.99×10^?7 to 3.85×10^?5 mol/l with a detection limit of 6.28×10^?7 mol/l. Three “spiked” samples of water were evaluated using the proposed sensor, and results agreed with those obtained by a reference method at the 95% confidence level.     

Poly(4-vinylpyridine-co-aniline)-modified electrode—synthesis, characterization, and application as cadmium(II) ion sensor

A poly(4-vinylpyridine-co-aniline) (poly(4VP-co-Ani))-based solid-state ion sensor for cadmium (Cd) was developed. This was obtained from studies done on a number of selected monomers electropolymerized onto a poly(4vinylpyridine) (P4VP)-modified graphite pencil rod, surface characterizing them and then analyzing their performances as a Cd(II) ion sensor. Among them, the membrane of poly(4VP-co-Ani) at a mole ratio of 0.05:0.15 was found to be the best. The fabricated poly(4VP-co-Ani) solid-state electrode had a linear response of 1?×?10^?6 to 1?×?10^?2?M Cd²⁺, slope of 29.4?±?0.5 mV decade^?1, detection limit of 7.94?×?10^?7?M Cd²⁺, and response time of 15 s at pH 4.5–8.5 with excellent selectivity. The sensor was operationally stable within a period of 3 months. The proposed sensor was tested for determination of Cd²⁺ in environmental, plant, and pharmaceutical samples. The analyses were comparable to the standard atomic absorption spectrophotometric method.     

Single-Sweep Voltammetric Determination of Tamoxifen at Carbon Paste Electrode

Abstract

A single-sweep voltammetric method was proposed for the determination of tamoxifen. The proposed method took advantage of both the accumulation of carbon paste electrode toward tamoxifen and the rapidity of single-sweep voltammetry. In HAc-NaAc (pH 4.1) buffer/methanol (85:15 v/v) mixed solution, an irreversible oxidation peak of tamoxifen was observed at 1.1 V (versus SCE). The second-order derivative peak current of tamoxifen and its concentration plots were rectilinear over the range of 7.0 × 10^?10 ～ 3.0 × 10^?8 mol · l^?1 with a detection limit of 1.0 × 10^?10 mol · l^?1 without any preconcentration. The proposed method was evaluated by analyzing tamoxifen citrate tablets, which was characterized by rapidity and higher sensitivity.     

A Novel Sensitive Method for the Determination of Cadmium and Lead Based on Magneto‐Voltammetry

Abstract

A novel method for the ultratrace determination of Cd²⁺ and Pb²⁺ based on magneto‐voltammetry was developed. In the presence of a low strength magnetic field of 0.6 T, square wave stripping voltammetry (SWSV) of Cd²⁺ and Pb²⁺ was performed in this determination. A high concentration of redox species Fe³⁺ was added to the analytes to generate a large cathodic current during the preconcentration step. A large Lorentz force arising from the flux of net current through the magnetic field resulted in convective solution flow due to magnetohydrodynamics. Then more metal ions deposited on the electrode surface at a faster rate and an enhancement as large as 160% for the stripping peak current was observed. Under the optimal conditions, this method exhibits high sensitivities of 5.67 µA µM^?1 for Cd²⁺ and 6.98 µA µM^?1 for Pb²⁺, over the 1×10^?8 – 1×10^?6 mol l^?1 range. Detection limits as low as 9.0×10^?10 and 8.6×10^?10 mol l^?1 for Cd²⁺ and Pb²⁺ were obtained with a 2 min preconcentration time, respectively. The method was successfully applied to detect Cd²⁺ and Pb²⁺ in real water samples and the results were in agreement with atomic absorption spectrometry.     

Preconcentration of tranquilizers by adsorption/extraction at a wax-impregnated graphite electrode

The tranquilizers promethiazine, diethazine, trifluoperazine, fluphenazine and clozapin adsorb at the surface and extract into the wax-impregnated graphite electrode (WIGE) as shown by chronocoulometry. Extraction/adsorption at the electrode serves as a preconcentration step which improves the limit of detection for the drugs by differential pulse voltammetry. A 15-min preconcentration gave a linear range of 10^?4–5 × 10^?8 M with a detection limit of 5 × 10^?9 M for clozapin in pH 7 phosphate buffer. The determination of tranquilizers in urine and plasma required no preliminary treatment; the detection limits were 5 × 10^?8 M in urine and 10^?7 in plasma. Plasma measurements were made at a WIGE covered with a Spectrapor membrane to prevent electrode fouling by protein adsorption.     

Trace metal enrichment by automated on-line column preconcentration for flow-injection atomic absorption spectrometry

An on-line column preconcentration technique for flow-injection atomic absorption spectrometry was developed. Diverse metal ions (Cd²⁺, Zn²⁺, Cu²⁺, Mn²⁺, Pb²⁺, Fe³⁺ and Cr³⁺) in solution were concentrated quantitatively by a microcolumn (7-mm × 4-mm i.d.) packed with Muromac A-1, which is an iminodiacetate chelate resin, in a flow-injection system. From the pH dependence of the uptake of the ions, all the divalent metals examined were recovered quantitatively in the pH range 3–5 and the trivalent metals were recovered at a maximum pH of 1. Enrichment factors using 20-ml samples were in the range 90–180-fold for the seven elements and the sampling rate was 13 h^?1. The 3σ detection limits were in the range 0.14–2.1 μg l^?1 and the relative standard deviations for replicate measurements (n=3–4) were in the range 0.7–1.7%. The method was compared with flame and graphite furnace atomic absorption spectrometry. Application to the determination of cadmium and copper in several standard reference materials is described.     

A multivariate calibration procedure for the tensammetric determination of detergents

A multivariate calibration procedure based on singular value decomposition (SVD) and the Ho-Kashyap algorithm is used for the tensammetric determination of the cationic detergents Hyamine 1622, benzalkonium chloride (BACl), N-cetyl-N,N,N-trimethylammonium bromide (CTABr) and mixtures of CTABr and BACl. The sensitivity and accuracy depend strongly on the nature of the detergent. Acceptable accuracy is obtained with a two-step calculation procedure in which calibration constants for the total concentration range of interest are used to guide the choice of a more specific set of calibration constants which are valid for a much smaller concentration span. For Hyamine 1622, concentrations in the range 5 × 10^?6?2 × 10^?4 M could be determined with an accuracy of ± 10^?6 M. For CTABr, these numbers were 3 × 10^?6?2 × 10^?4 M and ± 5 × 10^?7 M; for BACl, they were 2 × 10^?3?9 × 10^?2 g l^?1 and ± 1 × 10^?3 g l^?1. In the mixtures of CTABr and BACl, the accuracies were ± 3 × 10^?6 M and × 1 × 10^?3 g l^?1, respectively.     

An efficient flow-injection system with on-line ion-exchange preconcentration for the determination of trace amounts of heavy metals by atomic absorption spectrometry

A flow-injection system with on-line ion-exchange preconcentration on dual columns is described for the determination of trace amounts of heavy metals at μg l^?1 and sub-μg l^?1 levels by flame atomic absorption spectrometry. The degree of preconcentration ranges from 50- to 105-fold for different elements at a sampling frequency of 60 s h^?1. The detection limits for Cu, Zn, Pb and Cd are 0.07, 0.03, 0.5, and 0.05 μg l^?1, respectively. Relative standard deviations were 1.2–3.2% at μg l^?1 levels. The behaviour of the different chelating exchangers used was studied with respect to their preconcentration characteristics, with special emphasis on interferences encountered in the analysis of sea water.     

Flow Injection and Batch Spectrophotometric Determination of Ibuprofen Based on its Competitive Complexation Reaction with Phenolphthalein‐β‐Cyclodextrin Inclusion Complex

Abstract

Rapid, simple, and accurate spectrophotometric method is presented for the determination of ibuprofen by batch and flow injection analysis methods. The method is based on ibuprofen competitive complexation reaction with phenolphthalein‐β‐cyclodextrin (PHP‐β‐CD) inclusion complex. The increase in the absorbance of the solution at 554 nm by the addition of ibuprofen was measured. Ibuprofen can be determined in the range 8.0×10^?6 ?3.2×10^?4 and 2.0×10^?5?5.0×10^?3 mol l^?1 by batch and flow methods, respectively. The limit of detection and limit of quantification were 6.19×10^?6 and 2.06×10^?5 mol l^?1 for batch and 1.77×10^?5 and 5.92×10^?5 mol l^?1 for flow method, respectively. The sampling rate in flow injection analysis method was 120±5 samples h^?1. The method was applied to the determination of pharmaceutical formulations.     

Anodic stripping voltammetry at a nickel-based mercury film electrode

The electrochemical properties of the nickel-based mercury film electrode (Ni-MFE) were investigated with respect to application of the electrode in the anodic stripping voltammetry (a.s.v.) of heavy metal ions. The hydrogen overpotential at the Ni-MFE is higher than those at MFEs based on other metals, and high enough to get quantitative a.s.v. peaks of lead and cadmium. The mercury film of the Ni-MFE is stable both mechanically and chemically; a.s.v. peaks at a Ni-MFE which had been used fifty times within 300 h after its preparation were identical with those at the freshly prepared electrode. With the Ni-MFE, 5 × 10^?10–10^?7 M lead(II) and 2 × 10^?10–10^?7 M cadmium(II) in the solution can be determined with relative standard deviations of 11 and 12%, respectively. These results are comparable to those obtained by a.s.v. at an in situ mercury-plated g]assy carbon electrode.     

A new reagent for the spectrophotometric microdetermination of cadmium

2,2′-Dipyridyl-2-pyridylhydrazone (DPPH) allows a simple, rapid, and sensitive spectrophotometric microdetermination of cadmium in aqueous solution. The yellow 1:2 metal-to-ligand complex formed has a molecular extinction coefficient of 5.5 × 10⁴ liters mole^?1 cm^?1 at the absorption maximum of 444 nm. The determination of cadmium is carried out at pH 12.3 ± 0.2. Beer's law is obeyed over the concentration range of 0.2 to 2 ppm and the Sandell sensitivity of the color reaction is 0.002 μg of cadmium/cm² for an absorbance of 0.001.     

Determination of traces of streptomycin and related antibiotics by adsorptive stripping voltammetry

Adsorptive stripping voltammetry provides sensitive determinations of trace amounts of the saccharide-related antibiotics, streptomycin, erythromycin and novobiocin. A static mercury drop electrode is immersed in a stirred alkaline solution of the drug for a fixed time (60–300 s) at a suitable potential, and the adsorbed species is then stripped in the linear-scan or differential-pulse mode. The preconcentration potentials and stripping peak potentials (vs. Ag/AgCl) are, respectively, ?1.0 V and ?1.58 V for streptomycin, ?0.9 V and ?1.2 V for erythromycin, and ?1.0 V and ?1.38 V for novobiocin. The interfacial behavior is discussed. Short preconcentration periods suffice to quantity streptomycin, novobiocin, and erythromycin down to the 7 × 10^?10 M, 2.5 × 10^?9 M, and 1.3 × 10^?8 M levels, respectively. Streptomycin added to urine can be quantified after simple dilution.