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A new solid-contact ion-selective electrode (ISE) sensitive to lead (II) ions, obtained by modifying a polymer membrane with a nanocomposite of carbon nanofibers and an ionic liquid 1-hexyl-3-methylimidazolium hexafluorophosphate, is presented. Electrodes with a different amount of nanocomposite in the membrane (0–9% w/w), in which a platinum wire or a glassy carbon electrode was used as an internal electrode, were tested. Potentiometric and electrochemical impedance spectroscopy measurements were carried out to determine the effect of the ion-sensitive membrane modification on the analytical and electrical parameters of the ion-selective electrode. It was found that the addition of the nanocomposite causes beneficial changes in the properties of the membrane, i.e., a decrease in resistance and an increase in capacitance and hydrophobicity. As a result, the electrodes with the modified membrane were characterized by a lower limit of detection, a wider measuring range and better selectivity compared to the unmodified electrode. Moreover, a significant improvement in the stability and reversibility of the electrode potential was observed, and additionally, they were resistant to changes in the redox potential of the sample. The best parameters were shown by the electrode obtained with the use of a platinum wire as the inner electrode with a membrane containing 6% of the nanocomposite. The electrode exhibited a Nernstian response to lead ions over a wide concentration range, 1.0 × 10−8–1.0 × 10−2 mol L−1, with a slope of 31.5 mV/decade and detection limit of 6.0 × 10−9 mol L−1. In addition, the proposed sensor showed very good long term stability and worked properly 4 months after its preparation without essential changes in the E0 or slope values. It was used to analyze a real sample and correct results of lead content determination were obtained. [ABSTRACT FROM AUTHOR]

A method for direct potentiometric determination of lead(II) ion in native, untreated environmental samples of groundwater is reported. In a filtered sample, when applying a solid-state (PbS/Ag2S) ion-selective electrode in tuned galvanostatic polarization (TGP) mode, a concentration of 17.2±1.6 µg dm−3 was measured. The potentiometric results are compared with those obtained using inductively coupled plasma mass spectrometry (ICP-MS), 18.0±0.4 µg dm−3 and differential pulse anodic stripping voltammetry (DPASV), 24.3±0.5 µg dm−3. Owing to limitations of other methods, the analysis of Pb2+ in the untreated and non-filtered samples was only possible with the ion-selective electrode solid-state electrode. The described method can be an attractive alternative to existing methods of Pb2+ determination that are used to monitor groundwater pollution. [ABSTRACT FROM AUTHOR]

• An integrated potentiometric sensor includes a Cu2+-ISE as an indicator electrode and an Ag/AgCl electrode with a PVB reference membrane is developed. • Self-assembled porous graphene aerogels (PGAs) used as solid contact were prepared through an electrodeposition method. • The potentiometric sensor shows a stable potential response with a small potential drift. An integrated all-solid-state screen-printed ion-selective potentiometric sensor for the determination of Cu2+ is proposed. The whole-cell potentiometric sensor incorporates a polymeric membrane copper ion-selective electrode (Cu2+-ISE) as an indicator electrode and an Ag/AgCl reference electrode with a polyvinyl butyral reference membrane. The three-dimensional (3D) self-assembled porous graphene aerogel (PGA) can be conveniently and rapidly electrodeposited on the electrode substrate surface. Due to its interior 3D interconnected porous structures, the PGA has a large electrical double layer capacitance and fast charge transfer capability, which make it promising to be used as solid contact for the fabrication of the Cu2+-ISE. The developed potentiometric sensor shows a good Nernstian response over a range from 10−6 to 10−3 M with a detection limit of 10−6.5 M. In addition, the sensor exhibits a stable potential response with the absence of an undesirable water layer at the ion-selective membrane/PGA interface. [ABSTRACT FROM AUTHOR]