Determination of trace arsenic with DDTC-Na by cathodic stripping voltammetry in presence of copper ions

Electrochemistry at Krakowian research institutions

The electrochemistry research team activity from Poland is marked by significant increase in the last 20 years. The joining of European Community in 2004 gives an impulse for the development of Polish science. The development of electrochemistry has been stimulated by cooperation with industry and the establishment of technology transfer centers, technology parks, business incubators, etc. and the mostly by simplified international collaborations. Five research institutions from Krakow reports work in the field of electrochemistry. The achievements of all teams are briefly described.

Ultrathin quasi-hexagonal gold nanostructures for sensing arsenic in tap water

Monodispersed colloidal gold nanoparticles (AuNPs) were synthesized by an easy, cost-effective, and eco-friendly method. The AuNPs were mostly quasi-hexagonal in shape with sizes ranging from 15 to 18 nm. A screen-printed electrode modified with AuNPs (AuNPs/SPE) was used as an electrochemical sensor for the detection of As(iii) in water samples. The mechanistic details for the detection of As(iii) were investigated and an electrochemical reaction mechanism was proposed. Under the optimal experimental conditions, the sensor was highly sensitive to As(iii), with a limit of detection of 0.11 μg L-1 (1.51 nM), which is well below the regulatory limit of 10 μg L-1 established by the United States Environmental Protection Agency and the World Health Organization. The sensor responses were highly stable, reproducible, and linear over the As(iii) concentration range of 0.075 to 30 μg L-1. The presence of co-existing heavy metal cations such as lead, copper, and mercury did not interfere with the sensor response to As(iii). Furthermore, the voltammogram peaks for As(iii), lead, copper, and mercury were sufficiently separate for their potential simultaneous measurement, and at very harsh acidic pH it may be possible to detect As(v). The AuNPs/SPE could detect As(iii) in tap water samples at near-neutral pH, presenting potential possibilities for real-time, practical applications.

Determination of Se(IV) concentration via cathodic stripping voltammetry in the presence of Cu(II) ions and ammonium diethyl dithiophosphate

The development of a methodology for the determination of Se(IV) concentration via cathodic stripping voltammetry is described in this work. The methodology is based on the formation of copper selenide (Cu₂Se), whose reduction signal at -0.60 V has been used as an analytical response to quantify the Se(IV) concentration in solution. The novelty of our methodology is the study of this system in the presence of a ligand such as ammonium diethyl dithiophosphate (ADTTP), which forms complexes with Cu(II) and Se(IV). The results showed that the presence of ADTTP plays an important role, increasing the sensitivity of the determination by almost a factor of two compared with the methodology in the absence of the ligand. The optimized conditions were pH 1.6 (phosphoric acid, 2.0 × 10^-2 mol L^-1), C_Cu(II) = 1.5 mg L^-1, C_ADTTP = 2.0 μmol L^-1, E_acc = -0.40 V and t_acc = 45 s. The detection and the quantification limits obtained were 0.065 and 0.21 μg L^-1, respectively, and linearity was maintained up to 4.0 μg L^-1 of Se(IV). The sensitivity was 10.26 nA L μg^-1. On the other hand, the relative standard deviation for 15 replicate measurements at 1.0 μg L^-1 of Se(IV) was 1.6%. The usefulness of the method was evaluated by determining Se(IV) in two certified reference materials (TMDW and TM-28.4) with relative errors of less than 2.0%. The proposed method was successfully applied to the determination of Se(IV) in spiked tap water and in a liquid pharmaceutical formulation with satisfactory results. The developed methodology presents a low detection limit, good repeatability, selectivity and linear range. Furthermore, the sensibility of the method was achieved by applying a short accumulation time (45 s).

A novel spectrofluorometric method for the determination of arsenic in human hair using Dy2O3-doped CeO2nanoparticles

This paper describes a novel spectrofluorometric method for the determination of arsenic in human hair using Dy₂O₃-doped CeO₂nanoparticles.

The molecular resonance fluorescence method for determination of arsenic in hair samples

A molecular resonance fluorescence quenching method for the determination of arsenic was proposed. The method is based on the quenching effect of As (V) on the molecular resonance fluorescence of Rhodamine B (RhB) in sulfuric acid medium and in the presence of molybdate and PVA. The influences of acidity, chemical and manifold variables on the sensitivity were studied. At the optimized conditions, the linear range for the determination of arsenic was 2.0x10(-3)-0.12microgml(-1) with the detection limit of 1.20x10(-9)gml(-1). The relative standard deviations for the eleven replicate determinations of 0.006microgml(-1) and 0.060microgml(-1) of arsenic were 1.12% and 1.61%, respectively. The proposed method was applied successfully for the determination of trace arsenic in hair samples with the recoveries of 94.8-104.6%.

Development of a Microelectrode Array Sensing Platform for Combination Electrochemical and Spectrochemical Aqueous Ion Testing

A microelectrode array sensor platform was designed and fabricated to increase diversity, flexibility, and versatility of testing capabilities over that of traditionally reported sensor platforms. These new sensor platforms consist of 18 individual addressable microelectrodes, photolithography fabricated, that employ a glass base substrate and a resist polymer layer that acts as an insulating agent to protect the circuitry and wiring of the sensor from undesired solution interactions. Individually addressable microelectrodes increase diversity by allowing isolated electrochemical testing between electrodes, global array testing, or some combination of electrodes to perform electrochemical methods. Furthermore, because of the optical transparency of the glass base substrate and the resist mask layer, along with the small size of the electrode array, spectrochemical analysis is possible within the sample area that acts as electrochemical cell and cuvette, while the microelectrode array passively resides within the optical path length during spectrochemical testing. This unique arrangement offers improved testing possibilities for various applications, including simultaneous electrochemical and spectrochemical analysis in environmental testing, identification or quantification of possible species for bioavailability in the biotechnology field, and process control in industrial applications. Electrochemical characteristics and spectrochemcial use of the sensor platform are proven with potassium ferricyanide, an electrochemical standard analyte, and electrochemical measurements are compared against a commercially available working electrode of similar size. Additionally, the electrochemical method of differential pulse anodic stripping voltammetry is performed with the sensor platform to detect copper and lead heavy metal ions in aqueous solution, demonstrating the potential for use with environmental samples.

Cathodic stripping voltammetric determination of As(III) with in situ plated bismuth-film electrode using the catalytic hydrogen wave

A highly sensitive method has been developed for the determination of trace As(III) by a square wave cathodic stripping voltammetry employing in situ plated bismuth-film on edge-plane graphite substrate as working electrode. The presence of As(III) enhanced a cathodic peak corresponding to the catalytic hydrogen wave due to Se(IV) at about -1150 mV. Linear calibration curves for As(III) determination were obtained over the concentration ranges of 0.01-1.0 microg L(-1) and 1.0-12.0 microg L(-1) at deposition times of 30 s and 10 s, respectively. The detection limit (3sigma) was estimated to be as low as 0.7 ng L(-1) As(III) at 30 s deposition time. The optimum experimental parameters and probable interference from foreign ions and organic compounds were investigated. This proposed method could be applied to analyses of certified reference material, synthetic and natural water samples.