Arsenic in the aquatic environment

Arsenic species in the aquatic environment have been investigated following the development of appropriate techniques. The silver diethyldithiocarbamate (SDDC) colorimetric method and an automated procedure using hydride generation atomic absorption spectrophotometry were applied to the assessment of &quot;total&quot; arsenic levels, these techniques having detection limits of 0.1 pg/ml and 0.9 ng/ml respectively. &quot;Inorganic&quot; arsenic(III) and arsenic(V), &quot;methylarsenic&quot; and &quot;dimethylarsenic&quot; were determined by selective volatilisation of arsines into a heated quartz atomiser atomic absorption spectrophotometer (detection limit 0.25 ng). Interferences were investigated and overcome by suitable pretreatment procedures. Extraction and ashing procedures were studied for the determination of both &quot;total&quot; arsenic and specific arsenic species. &quot;Inorganic&quot; arsenic(III) and arsenic(V), &quot;methyiarsenic&quot; and &quot;dimethylarsenic&quot; were detected in water samples from the estuaries of the rivers Beaulieu and Test. &quot;Inorganic&quot; arsenic(III), &quot;methylarsenic&quot; and &quot;dimethylarsenic&quot; levels were found to apparently depend on water temperature. Dissolved &quot;inorganic&quot; arsenic behaves non-conservatively in the Beaulieu Estuary; laboratory mixing experiments indicating arsenic removal from the water at salinities below 200 .Arsenic in macroalgae and molluscs was found to be present as organoarsenic species which degrade to &quot;dimethylarsenic&quot; species on extraction and analysis. Water-soluble arsenic compounds extracted from molluscs (NueeZZa Zapillua and Littorina Zittorea) were identified as dimethylarsinate, arsenite and arsenate. Lipidsoluble arsenic in the molluscs was polar and behaved chromatographically and enzymatically as phosphatidylethanolamine.</p

The response behavior of PPy-DB18C6 electrode to terbium(III) in acetonitrile and its thermodynamic application

Polypyrrole modified electrode prepared by electropolymerization of pyrrole in the presence of a complexing ligand, dibenzo-18-crown-6(DB18C6), was prepared and investigated as a Tb3+-selective electrode in acetonitrile. The potentiometric response of the electrode was linear within the Tb3+ concentration range 1 × 10−5–1 × 10−2 M with a Nernstian slope of 20.9 mVdecade−1 in AN. The electrode was applied to study the complexation of the terbium(III) ion in acetonitrile with such other basic aprotic solvent molecules (D) as dimethyl sulfoxide, N,N-dimethyl formamide, propylene carbonate and pyridine. The successive complex formation constant (βi) and Gibbs energies of transfer (ΔGtr) of Tb3+ in AN in relation to such D were obtained

A PPy-B15C5 modified lanthanum (III) electrode in acetonitrile and its thermodynamic application

Polypyrrole modified electrode prepared by electropolymerization of pyrrole in the presence of a complexing ligand, benzo-15-crown-5 (B15C5), was prepared and investigated as a La3+-selective electrode in acetonitrile. The potentiometric response of the electrode was linear within the La3+ concentration range 1 × 10−4 to 1 × 10−1 M with a Nernstian slope of 19.5 mV decade−1 in AN. The electrode was applied to study the complexation of the lanthanum (III) ion in acetonitrile with other basic solvent molecules (D) such as dimethyl sulfoxide, N,N-dimethylformamide, propylene carbonate, N,N,Diethylaniline and methanol. The successive complex formation constant (βi) and Gibbs energies of transfer (ΔGtr) of La3+ in AN in relation to such D were obtained

Preconcentration of lead using solidification of floating organic drop and its determination by electrothermal atomic absorption spectrometry

A simple microextraction method based on solidification of a floating organic drop (SFOD) was developed for preconcentration of lead prior to its determination by electrothermal atomic absorption spectrometry (ETAAS). Ammonium pyrolidinedithiocarbamate (APDC) was used as complexing agent, and the formed complex was extracted into a 20 μL of 1-undecanol. The extracted complex was diluted with ethanol and injected into a graphite furnace. An orthogonal array design (OAD) with OA16 (45) matrix was employed to study the effects of different parameters such as pH, APDC concentration, stirring rate, sample solution temperature and the exposure time on the extraction efficiency. Under the optimized experimental conditions the limit of detection (based on 3 s) and the enhancement factor were 0.058 μg L−1 and 113, respectively. The relative standard deviation (RSD) for 8 replicate determinations of 1 μg L−1 of Pb was 8.8%. The developed method was validated by the analysis of certified reference materials and was successfully applied to the determination of lead in water and infant formula base powder samples

Nano-level Monitoring of Yttrium by a Novel PVC-membrane Sensor Based on 2,9-dihydroxy-1,10-diphenoxy-4,7-dithiadecane

A poly (vinyl chloride)-based membrane of 2,9-dihydroxy-1,10-diphenoxy-4,7-dithiadecane (C20H26O4S2) as a neutral carrier was prepared and investigated as an Y3+-selective electrode. Effects of various plasticizers and anion excluders were studied in detail and improved performance was observed. The best performance was obtained for the membrane sensor having a composition of L: PVC: NPOE: PA in the ratio of 2:30:62:6 (mg). The performance of the membrane was found to be the following: A Nernstian slope of 20.0 ± 0.2 mV per decade across a broad range (1.0 × 10−9 to 1.0 × 10−1 mol dm–3); a detection limit of 2.14 × 10–10 mol dm–3 between the pH = 4.5 and 9.0; additionally, the response time was about 15 s; good Y3+ selectivity over a wide variety of other metal ions. The membrane sensor was applied as an indicator electrode in potentiometric titration of fluoride ion and also used for determination of F− ion in tap water and toothpaste samples. (doi: 10.5562/cca1937

Ion imprinted polymer based potentiometric sensor for the trace determination of Cadmium (II) ions

A cadmium (II) ion selective electrode (ISE) based on an ion-imprinted polymer (IIP) as a novel ionophore has been prepared and studied. The ion-selective electrode (ISE) was prepared by dispersing cadmium (II) IIP particles in 2-nitrophenyloctyl ether as a plasticizer and then embedding them in a polyvinylchloride polymeric matrix. The Cd(II) ISE showed a nernstian response for cadmium (II) over the dynamic concentration range of 2.0 × 10−7–1.0 × 10−2 mol L−1, with a slope of 29.9 mV per decade. The limit of detection was 1.0 × 10−7 M. The proposed electrode revealed good selectivity over a wide variety of other cations including alkali, alkaline earth, heavy and transition metals. The accuracy of the proposed electrode was checked through the analysis of spiked water samples

On/off-switchable electrochemical folic acid sensor based on molecularly imprinted polymer electrode

The combination of smart polymers with molecular imprinting offers a powerful tool to design more effective sensors and medical devices. In this study, a temperature sensitive amine-terminated poly(N-isopropylacrylamide) block with (N,N'-methylenebisacrylamide) cross-linker along with o-phenylenediamine was electropolymerised on a gold electrode in the presence of folic acid (FA) as template to produce an on/off-switchable molecularly imprinted polymer (MIP) affinity sensor for folic acid. Differential pulse voltammetry and cyclic voltammetry were used to characterise the FA-imprinted layer. Incubation of the MIP-modified electrode with FA resulted in a suppression of the ferro/ferricyanide redox process. The highest sensitivity of this temperature gated on/off-switchable folic acid sensor was achieved at 22 °C. Such switchable affinity materials offer considerable potential for the design of highly selective and controllable biosensors and immunoassays. Keywords: Molecularly imprinted polymer, Smart polymers, Temperature switchable electrode, Folic acid electrochemical senso