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[Display omitted] • Mobility of species and ionic behavior of [C 6 Meim][NTf 2 ] in plasticized PVC were studied using PFG NMR method. • Both individual ions and an ion pair of [C 6 Meim][NTf 2 ] are present in PVC membrane. • Diffusion coefficients for both forms decrease with increasing [C 6 Meim][NTf 2 ] content. • Electrolytic properties depend nonmonotonically on the [C 6 Meim][NTf 2 ] content. • Maximum apparent dissociation constant was registered in a membrane with 30 wt% of [C 6 Meim][NTf 2 ] Ionic liquids (ILs) are increasingly used as promising organic solvents for a variety of applications, including electrochemical processes, novel separation techniques and innovative methods of synthesis, due to their low volatility, excellent solvation properties, high ionic conductivity and electrochemical stability. Moreover, the tunable properties of ILs determined by their composition make them favorable candidates as dopants for composite and/or functional polymeric materials, e.g. in the membranes of chemical sensors. To effectively use ILs in polymeric materials and control the characteristics of the latter, one should develop a complete understanding of the properties of ILs in the polymeric phase, such as their diffusion and ionic behavior. In our previous work, we applied pulsed field gradient (PFG) NMR technique to verify the results of a chronopotentiometric method conventionally used to determine the diffusion coefficients and electrolytic properties of electrolytes in plasticized poly(vinyl chloride) (PVC) membranes of chemical sensors. The results obtained with these two independent methods were in good agreement, confirming that PEG NMR diffusometry is a viable technique for assessing the diffusion properties of species even in highly viscous polymeric media of low polarity. Here we report a comprehensive study of the transport and ionic behavior of IL 1-hexyl-3-methyl-1 H -imidazolium bis[(trifluoromethyl)sulfonyl]amide ([C 6 Meim][NTf 2 ]) in a poly(vinyl chloride) matrix, performed in situ by means of PFG NMR diffusometry. A number of sets of spectra for the 1H and 19F nuclei of the [C 6 Meim][NTf 2 ] ionic liquid in PVC membranes doped with the plasticizer bis(2-ethylhexyl)sebacate were registered at different amplitudes of the magnetic field gradient. The mobility of both individual ions of the IL and the formed ion associates was investigated over a broad range of IL concentrations in the PVC matrix; in addition, the ionization degree and dissociation constant of [C 6 Meim][NTf 2 ] were determined and their dependence on the IL content was traced. [ABSTRACT FROM AUTHOR]

In this paper we report on the novel polymeric membranes for the liquid junction‐free reference electrodes. The membranes contain the ionic liquids (ILs) based on the amino acid anions, namely valine‐, leucine‐, lysine‐ and histidine‐anions, and 1‐butyl‐3‐methylimidazolium cation. Addition of the ILs, and especially of the valine‐based one, to the polymeric plasticized membranes allows significant stabilization of the electrode potential and makes it insensitive to the solution composition. A simple criterion based on the calculated lipophilicities of the cation and anion of the IL is proposed for a priori estimation of its applicability for potential stabilization. The addition of the IL as a microcomponent is found to be advantageous over plasticizing the membrane with the IL due to better potential stability, higher dissociation degree and mobility of the species. The resistance of the novel reference membranes can be tuned by addition of the lipophilic membrane electrolytes, e. g. ETH500. The applicability of the developed reference electrodes is verified in the potentiometric calibration of the indicator K+‐ and Ca2+‐selective electrodes. Implementation of the amino acid‐based ionic liquids with low environmental toxicity can make a significant contribution to the development of nature‐friendly potentiometry. [ABSTRACT FROM AUTHOR]

Abstract The indicator-based polymeric color standards for color referencing in digital color analysis (DCA) of optical chemical sensors (optodes) are proposed. In the novel standards, the colors referring to the actual absorption bands of the protonated and deprotonated forms of the indicator are mixed in constant proportions. The standards are based on the lipophilic pH-indicators: ETH5350 and ETH2439, commonly used in optodes, and the lipophilic electrolyte TBATBB. The dependence of the standard color on the TBATBB concentration in the optode is established and found to be linear. The standard colors remain unchanged upon varying the solution pH and the nature and the concentration of the electrolyte. Calibration curves of the indicator pH-optodes obtained in horse serum and referenced to the developed standards demonstrate lower error to span ratio, broader span and higher sensitivity as compared to the same data processed with the conventional gray standard. The colorimetric signal of the pH-optodes array measured in serum sample and referenced to the developed standards allowed accurate determination of the sample pH thus demonstrating practical prospects of the proposed color standards. Graphical abstract fx1 Highlights • Indicator-based polymeric color standards were developed for digital color analysis. • The standard color can be tuned by changing composition of the polymeric membrane. • The developed color standards are independent on the solution composition. • The color standards are applicable for digital color analysis with optodes in serum. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Numerical simulations of analytical characteristics of bulk optodes are performed. • Effect of the composition in the optode span, range, sensitivity is evaluated. • Response curves with intermediate plateau are predicted and obtained experimentally. • Algorithms for the fine-tuning of the optode response are developed. • The simulations are verified with Na+- and K+-selective colorimetric optodes. Abstract The response characteristics of the optical chemical sensors (optodes), namely response range, response span and sensitivity are quantitatively related to the composition of the sensor phase for the first time. The dependence of the characteristics of ion-selective bulk optodes on the concentrations of the indicator, ionophore and ionic additive (ion-exchanger) are simulated numerically and experimentally verified with Na+- and K+-selective colorimetric optodes. It is shown how the response span, response range, median and sensitivity depend on the sensor membrane composition. Response curves with an intermediate plateau are predicted theoretically and obtained experimentally. It is shown that the inflection point in the response curve does not necessarily refers to α = 0.5. The results can be used for the fine tuning of the optical response of chemical sensors. [ABSTRACT FROM AUTHOR]

[Display omitted] • DCA precision can be adjusted by optimizing light source/detector/color space system. • Robustness criterion was applied to evaluate performance of 4 detector/color space systems. • Optimal detector/color space system may depend on the indicator nature in optodes. • Robustness criterion can be used to optimize a reporting dye for any specific DCA variation. Digital color analysis (DCA) of colorimetric and luminescent assays is rapidly spreading in analytical routine. However, the inconsistency of the illumination systems and reading devices, as well as the imperfect choice of the color components for DCA, may result in significant reduction of signal amplitude and in overall response deterioration. An adequate comparison of existing approaches to detection and processing of colorimetric signals in terms of precision of the acquired data is necessary in order to develop an unequivocal criterion for the device and color space selection. We show here that the robustness parameter can serve as such a criterion regardless of the analytical task, the origin of the colorimetric signal/response and the available instrumentation, and propose a comprehensive approach to optimization of the light source, the reading device, and the color space for the analysis of colorimetric assays. Combinations of incandescent lamps with a digital camera as well as red, green and blue LEDs with a monochrome camera were used for signal acquisition. Normalized Red, Green, Blue (RGB) and Hue, Saturation, Value (HSV) color spaces were used for DCA. Each combination of acquisition technique and processing algorithm was tested with a set of chromoionophore-based polymeric optodes, and characterized in terms of robustness. [ABSTRACT FROM AUTHOR]