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This paper presents a comparative study on the temperature resistance of solid-contact ion-selective electrodes, depending on the type of solid-contact material. Five types of potassium electrodes, with a valinomycin-based model membrane, were developed using different types of mediation layers, namely a conductive polymer (poly(3-octylthiophene-2,5-diyl) and a perinone polymer), multi-walled carbon nanotubes, copper(II) oxide nanoparticles, and a nanocomposite consisting of multi-walled carbon nanotubes and copper(II) oxide. We examined how the measurement temperature (10 °C, 23 °C, and 36 °C) affects the sensitivity, measurement range, detection limit, selectivity, as well as the stability and reversibility of the electrode potential. Electrodes modified with a nanocomposite (GCE/NC/ISM) and a perinone polymer (GCE/PPer/ISM) showed the best resistance to temperature changes. An almost Nernst response and a stable measurement range and the lowest detection limit values for each temperature were obtained for them. The introduction of mediation layers significantly improved the stability and potential reversibility of all the modified electrodes relative to the unmodified electrode (GCE/ISM). Still, it was the GCE/PPer/ISM and GCE/NC/ISM that stood out from the others, with stability of 0.11 and 0.12 µV/s for 10 °C, 0.05 and 0.08 µV/s for 23 °C, and 0.06 and 0.09 µV/s for 36 °C, respectively. [ABSTRACT FROM AUTHOR]

This paper proposes a simple, environmentally friendly, and efficient procedure for preparing natural water samples for the voltammetric determination of trace amounts of Se(IV). The method is based on premixing a sample with Amberlite XAD-7 resin at 50 °C. The composition of the 10 mL solution consists of the sample to be analysed, 0.1 mol L−1 of acetate buffer at pH = 4.0, and 0.5 g of Amberlite XAD-7. After 2 min of stirring, a voltammetric measurement is carried out using a fixed bismuth microelectrode using the following potentials: −2.5 V for 2 s and −0.55 V for 30 s. The voltammetry is recorded by varying the potential from −400 mV to −1000 mV. An undisturbed Se(IV) signal is obtained in the presence of 10 mg L−1 of Triton X-100, 5 mg L−1 of SDS, 10 mg L−1 of CTAB, 5 mg L−1 of Rhamnolipid, 5 mg L−1 of HA, 10 mg L−1 of FA, and 2 mg L−1 of NOM. The validity of the developed procedure is checked by analysing the certified reference materials SPS-SW1 (surface water) and TM-25.5 (Lake Ontario water) additionally enriched with surfactants and humic substances. [ABSTRACT FROM AUTHOR]

The extraction of total Cr(VI) from commercially available cements, based on DTPA + 0.2 mol dm -3 (NH4)2SO4/NH4OH mixture solution and subsequent selective determination of Cr(VI) has been proposed. The determination was carried out using the adsorptive voltammetric stripping method. The study was conducted using three different commercially available cement samples. It has been checked that the proposed extraction procedure guaranteed no changes of chromium speciation during cement analysis. For comparison extraction was also carried out with the use of recommended by United States Environmental Protection Agency (EPA) Method 3060A, based on 0.28 mol dm -3 Na2CO3 + 0.5 mol dm -3 NaOH). Additionally, the extraction process was carried out using only distilled water as an extraction mixture which allows to evaluate concentration of only soluble Cr(VI) forms contained in cement. In all three cements, the content of soluble Cr(VI) was below 2 ppm, i.e. the limit value by European Union Directive 2003/53/EC. [ABSTRACT FROM AUTHOR]

Nitrates are a group of compounds widely distributed in the natural environment with many applications in various industries. Due to their ambiguous impact on the human body and suspicions of their carcinogenic activity, they have been very popular for decades and are the subject of research by many scientists in the field of medicine, biology and chemistry. Due to the need to monitor their content in environmental and food samples, various methods for their determination are developed. This paper proposes the use of a nitrate ion‐sensitive ion selective electrode with a membrane containing as the active ingredient a new cobalt(II) complex with 4,7‐diphenyl‐1,10‐phenanthroline (Bphen) of the formula Co(Bphen)2(NO3)2(H2O)2. The obtained sensor showed the theoretical slope of the characteristic curve, a wide measuring range, as well as short response time and very good potential stability. It was successfully used for the determination of nitrates in real samples: in mineral water, tap water and river water from eastern Poland. [ABSTRACT FROM AUTHOR]