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The application of a potentiometric pH electrode in ocean acidification observation is still a challenge due to its poor sensitivity to small pH changes. Herein, a simple approach to remarkably improve the detection precision of a polymeric membrane ion-selective electrode is proposed based on the potential-modulated ion transfer mechanism. The present sensing strategy displays highly sensitive responses to small pH changes for seawater analysis with a precision of 5 μpH, which is 2 orders of magnitude lower than that of the conventional pH electrode.

Nowadays, using a potentiometric ion sensor to achieve detection of biological analytes is still a big challenge, since these analytes usually do not yield a measurable ion signal. To address this challenge, a simple and robust potentiometric sensing protocol based on a delayed Nernstian response is proposed for the label-free detection of biological analytes. The proposed sensor platform is composed of two layers: the surface recognition layer and the indicator-ion-selective electrode (ISE) membrane layer. It is based on a surface blocking mechanism in which the surface recognition interactions between the surface recognition element and the target can impede the diffusion of the indicator ion from the aqueous phase to the sensing membrane phase to reach the final Nernstian-response equilibrium, thus resulting in a delayed potential change. Such a potential change could be used to measure the concentration of a biological target in the sample. Thus, a sensing system was designed by using phage MS2, its host bacterium Escherichia coli ATCC 15597(abbreviated as E. coli H), and a solid-contact butyrylcholine ISE as a surface recognition element, a target, and an indicator electrode, respectively. This new concept offers a simple, sensitive, and extremely selective potentiometric method for detection of E. coli H with a detection limit of 100 CFU mL -1 . It can be expected that the present approach may pave the way to using ISEs to detect various important nonionic biological targets in clinical and environmental applications.

Nowadays, using a polymeric membrane ion-selective electrode (ISE) to achieve reliable ion sensing in complex samples remains challenging because of electrode fouling. To address this challenge, we describe a polymeric membrane ISE with excellent anti-fouling and self-cleaning properties based on surface covalent modification of an anatase TiO 2 coating. Under ultraviolet illumination, the reactive oxygen species produced by photocatalytic TiO 2 can not only kill microorganisms but also degrade organic foulants into carbon dioxide and water, and a formed superhydrophilic film can effectively prevent the adsorption of foulants, thus inhibiting the occurrence of biofouling and organic fouling of the sensors. More importantly, residual foulants could be fully self-cleaned through the flow of water droplets. By using Ca 2+ -ISE as a model, an anti-fouling polymeric membrane potentiometric sensor has been developed. Compared to the unmodified electrode, the TiO 2 -coated Ca 2+ -ISE exhibits remarkably improved anti-biofouling properties with a low bacterial adhesion rate of 4.74% and a high inhibition rate of 96.62%. In addition, the proposed electrode displays unique properties of anti-organic dye fouling and a superior self-cleaning ability even after soaking in a concentrated bacterial suspension of 10 9 CFU mL -1 for 60 days. The present approach can be extended to improve the fouling resistance of other electrochemical or optical membrane sensors and is promising for the construction of contamination-free sensors.

Molecularly imprinted polymer (MIP)-based polymeric membrane potentiometric sensors have been successfully developed for determination of organic compounds in their ionic and neutral forms. However, most of the MIP receptors in potentiometric sensors developed so far are insoluble and cannot be well dissolved in the polymeric membranes. The heterogeneous molecular recognitions between the analytes and MIPs in the membranes are inefficient due to the less available binding sites of the MIPs. Herein we describe a novel polymeric membrane potentiometric sensor using a soluble MIP (s-MIP) as a receptor. The s-MIP is synthesized by the swelling of the traditional MIP at a high temperature. The obtained MIP can be dissolved in the plasticized polymeric membrane for homogeneous binding of the imprinted polymer to the target molecules. By using neutral bisphenol AF as a model, the proposed method exhibits an improved sensitivity compared to the conventional MIP-based sensor with a lower detection limit of 60 nM. Moreover, the present sensor exhibits an excellent selectivity over other phenols. We believe that s-MIPs can provide an appealing substitute for the traditional insoluble MIP receptors in the development of polymeric membrane-based electrochemical and optical sensors.

Using sensors to quantify clinically relevant biological species has emerged as a fascinating research field due to their potential to revolutionize clinical diagnosis and therapeutic monitoring. Taking advantage of the wide utility in clinical analysis and low cost of potentiometric ion sensors, we demonstrate a method to use such ion sensors to quantify bioanalytes without chemical labels. This is achieved by combination of chronopotentiometry with a mussel-inspired surface imprinting technique. The biomimetic sensing method is based on a blocking mechanism by which the recognition reaction between the surface imprinted polymer and a bioanalyte can block the current-induced ion transfer of an indicator ion, thus causing a potential change. The present method offers high sensitivity and excellent selectivity for detection of biological analytes. As models, trypsin and yeast cells can be measured at levels down to 0.03 U mL -1 and 50 CFU mL -1 , respectively., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A method for the determination of tetrabromobisphenol A and bisphenol A in environmental water using carboxyl-functionalized multiwalled carbon nanotubes as solid-phase extraction sorbent and liquid chromatography-tandem mass spectrometry was established. Comparison of three nanomaterials including multiwalled carbon nanotubes, C60 and carboxyl-functionalized multiwalled carbon nanotubes used as solid-phase extraction sorbents was made. After preconcentration by solid-phase extraction, tetrabromobisphenol A and bisphenol A were separated on a Thermo Scientific Hypersil C18 column (150 mm x 4. 6 mm, 3 μm) and then detected by tandem mass spectrometry in negative electrospray ionization (ESI) mode. The results showed a good linear response in the concentration range of 0. 02-1. 0 mg/L for tetrabromobisphenol A and bisphenol A, and the limits of detection (S/N= 3) were 0. 04 pg/L and 0. 2 μg/L for tetrabromobisphenol A and bisphenol A, respectively. The application of the proposed approach has been carried out for the determination of tetrabromobisphenol A and bisphenol A in spiked lake water and sea water samples. The recoveries varied from 82% to 99% with the relative standard deviations below 5. 0%. The proposed method can be used for the determination of tetrabromobisphe- nol A and bisphenol A at trace level in complex environmental samples.