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Amino acids such as phenylalanine (Phe) are key building blocks of proteins and other biomolecules. Although recent advancements in electrochemical sensors have enabled the rapid detection of Phe, these sensors are often destructive as they irreversibly oxidise Phe. In addition, most of them rely on biorecognition elements, which suffer from limited stability at ambient conditions and sensitivity towards environmental fluctuations. Herein, we report the first example of ion transfer voltammetry of Phe using an all‐solid‐state ion‐selective electrode (ISE). The reversibility of this technique enables both the sensor and the Phe sample to be reused. The optimal voltammetric ISE (VISE) exhibits near Nernstian response (56.8 mV/decade) towards Phe and selectivity against amino acids of all classes (hydrophobic, hydrophilic and charged). Voltammetric interrogation of the ISE significantly enhances sensitivity, linear range, selectivity, and stability as compared to traditional open circuit potential measurements. Phe levels in a commercial nutritional supplement and drinking waters were determined to demonstrate the viability of our sensor in real life applications. This proof‐of‐concept can be applied to develop VISEs for other amino acids and biological ions for healthcare and nutrition sensing. [ABSTRACT FROM AUTHOR]

An all-solid-state polymeric membrane Ca2+-selective electrode based on hydrophobic octadecylamine-functionalized graphene oxide has been developed. The hydrophobic composite in the ion-selective membrane not only acts as a transduction element to improve the potential stability for the all-solid-state Ca2+-selective electrode, but also is used to immobilize Ca2+ ionophore with lipophilic side chains through hydrophobic interactions. The developed all-solid-state Ca2+-selective electrode shows a stable potential response in the linear range of 3.0×10−7-1.0×10−3 M with a slope of 24.7±0.3 mV/dec, and the detection limit is (1.6±0.2 )×10−7 M ( n=3). Additionally, due to the hydrophobicity and electrical conductivity of the composite, the proposed all-solid-state ion-selective electrode exhibits an improved stability with the absence of water layer between the ion-selective membrane and the underlying glassy carbon electrode. This work provides a simple, efficient and low-cost methodology for developing stable and robust all-solid-state ion-selective electrode with ionophore immobilization. [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]