Circumventing Traditional Conditioning Protocols in Polymer Membrane-Based Ion-Selective Electrodes

Preparation of ion-selective electrodes (ISEs) often requires long and complicated conditioning protocols limiting their application as tools for in-field measurements. Herein, we eliminated the need for electrode conditioning by loading the membrane cocktail directly with primary ion solution. This proof of concept experiment was performed with iodide, silver, and sodium selective electrodes. The proposed methodology significantly shortened the preparation time of ISEs, yielding functional electrodes with submicromolar detection limits. Moreover, it is anticipated that this approach may form the basis for the development of miniaturized all-solid-state ion-selective electrodes for in situ measurements

Simultaneous determination of calcium and potassium in coconut water by a flow-injection method with tubular potentiometric sensors

In the present work, a simultaneous determination of calcium and potassium in coconut water samples using a flow-injection system with tubular ion-selective electrodes (ISEs) in series is described. The samples were injected into a 0.1 mol L-1 HEPES (pH = 6.0) carrier solution, using an injection volume of 100 mu L and a flow of 2.0 mL min(-1) in the FIA system. The electrodes developed exhibited nernstian response for calcium and potassium in the concentration range between 1.0 x 10(-5) and 1.0 x 10(-1) mol L-1 with detection limits of 5.6 x 10(-6) mol L-1 for calcium and 9.5 x 10(-6) mol L-1 for potassium. And no significant interference between both ions was observed. The flow-injection analysis (FIA) system with tubular ISEs was suitable for the simultaneous calcium and potassium on-line monitoring. The determination of potassium presented good results when compared to the reference method. And the recovery results were 95 +/- 1% for calcium and 102 +/- 2% for potassium, showing a good evidence of the accuracy of the method. (c) 2005 Elsevier Inc. All rights reserved.194170022523

Solid contact potentiometric sensors for trace level measurements

A simple procedure for the development of a range of polymeric ion-selective electrodes (ISEs) with low detection limits is presented. The electrodes were prepared by using a plasticizer-free methyl methacrylate-decyl methacrylate copolymer as membrane matrix and poly(3-octylthiophene) as intermediate layer deposited by solvent casting on gold sputtered copper electrodes as a solid inner contact. Five different electrodes were developed for Ag+, Pb2+, Ca2+, K+, and I-, with detection limits mostly in the nanomolar range. In, this work, the lowest detection limits reported thus far with solid contact ISEs for the detection of silver (2.0 x 10(-9) M), potassium (10(-7) M), and iodide (10(-8) M) are presented. The developed electrodes exhibited a good response time and excellent reproducibility.7841318132

Determination of glutathione in hemolysed erythrocyte with amperometric sensor based on TTF-TCNQ

Background: GSH has a relevant role in human metabolism as an indicator of disease risks. An amperometric sensor for glutathione (GSH) determination is described as an alternative method featuring simple construction procedure and short time analysis. Method: The developed sensor was used to determine glutathione at low potential using a TTF-TCNQ complex. Results: The sensor exhibits a linear response range from 5 to 340 mu mol/l under applied potential of 200 mV vs. SCE. The sensitivity and detection limit were 90.1 mu A l/mmol cm(2) and 0.3 mu mol/l, respectively. Conclusion: When the sensor was tested in hemolysed erythrocyte samples for GSH determination, a good correlation in results was observed between the sensor and the spectrophotometric method. The sensor showed recovery values between 98% and 102%. (c) 2006 Elsevier B.V All rights reserved.3714167115215

Determination of reduced glutathione using an amperometric carbon paste electrode chemically modified with TTF-TCNQ

The development of an amperometric sensor for the determination of reduced glutathione (GSH) is described. The sensor is based on tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) incorporated into the graphite powder/Nujol oil matrix. The electrooxidation of GSH was monitored amperometrically at 200 mV versus SCE (saturated calomel electrode). The amperometric response of the sensor was linearly proportional to the GSH concentration between 20 and 300 mumol l(-1), in 0.1 mol l(-1) phosphate buffer (pH 8.0), containing 0.1 mol l(-1) KCl and 0.5 mmol l(-1) Na(2)H(2)EDTA, as supporting electrolyte. The detection limit, considering signal/noise ratio equal three, was 4.2 mumol l(-1) for GSH and the repeatability obtained as relative standard deviation was of 5.1 % for a series of 10 successive measurements. (C) 2004 Elsevier B.V. All rights reserved.100333334

Synthesis and characterization of high-integrity solid-contact polymeric ion sensors

High-integrity solid-contact (SC) polymeric ion sensors have been produced by using spin casting and electropolymerization techniques in the preparation of the SC employing the conductive polymer, poly(3-octylthiophene) (POT). The physical and chemical integrity of the POT SCs have been evaluated using scanning electron microscopy (SEM), atomic force microscopy (AFM), secondary ion mass spectrometry (SIMS), and X-ray photoelectron spectroscopy (XPS). Furthermore, the electrochemical stability of SC polymeric ion sensors has been investigated using electrochemical impedance spectroscopy (EIS). The results of this study demonstrate that electropolymerization and spin casting methods also comprising annealing of the synthesized SC film are capable of producing SCs that are relatively free of imperfections such as pores and pinholes. This leads to electrochemically stable and robust polymeric ion sensors where the SC/sensor interface is resistant to the formation of a detrimental water layer that normally gives rise to spurious ion fluxes and a degradation in th