In Situ Potentiometric Monitoring of Nitrate Removal from Aqueous Solution by Activated Carbon and Ion Exchange Resin.

A nitrate selective electrode was used for real-time in situ potentiometric monitoring of a batch nitrate removal process using activated carbon and ion exchange resin. A plasticized polymeric membrane consisting of polyvinyl chloride, 2-nitrophenyl octyl ether and tridodecyl methyl ammonium chloride was incorporated into an ion-selective electrode body. First, the dynamic potential response of the electrode to nitrate was investigated.

Potentiometric Electronic Tongue for Quantitative Ion Analysis in Natural Mineral Waters.

The present paper addresses the development and use of a new potentiometric electronic tongue for both qualitative and quantitative characterization of natural mineral waters. The electronic tongue is particularly related to the conductivity and ion content of/in the water sample. The analytical system is based on six ion-selective electrodes whose membranes are formulated to provide either cationic or anionic response and considering plasticizers with different dielectric constants (bis(2-ethylhexyl) sebacate, 2-nitrophenyl octyl ether or tricresylphosphate), while keeping the polymeric matrix, i.

Inexpensive ion-selective electrodes for the simultaneous monitoring of potassium and nitrate concentrations in nutrient solutions.

A fast, simple and inexpensive potentiometric method has been developed for the determination of the major ions potassium and nitrate in nutrient solutions, by means of ion-selective electrodes (ISEs) based on plasticized polyvinyl membranes containing an ion-exchanger. Tridodecylmethylammonium chloride (TDMACl) and potassium tetrakis(4-chlorophenyl)borate (KTClPB) were used as ion-exchangers for the nitrate and potassium electrodes, respectively. Electrode membranes built with different plasticizers, bis-[2-ethylhexyl]-sebacate (DOS), tricresyl phosphate (TCP) and 2-nitrophenyloctyl ether (NPOE), were tested, and NPOE was selected.

A sustainable amperometric biosensor for the analysis of ascorbic, benzoic, gallic and kojic acids through catechol detection. Innovation and signal processing.

In this work, we present a new catechol amperometric biosensor fabricated on the basis of naturally available enzymes in common mushrooms. The biosensor response mechanism comprises the reduction of the quinone exclusively produced in the oxidation of the catechol present in the sample, which is catalyzed by tyrosinase enzyme. The new catechol biosensor has demonstrated excellent analytical performance at increasing catechol concentrations in the sample solution, which includes superior reproducibility for several electrodes and long-term stability.

Comparative enzymatic studies using ion-selective electrodes. The case of cholinesterases.

The application of traditional ion-selective electrodes for comparative enzymatic analysis was demonstrated for the first time in this study. A kinetic-potentiometric method based on the monitoring of the concentration of the ionic substrate involved in the enzymatic reaction catalyzed by different cholinesterases is used for this purpose. A comparative study was performed comprising both enzymatic assays using different ionic substrates and the corresponding inhibited reactions in presence of neostigmine (a synthetic anticholinesterase).

Theoretical Treatment of Ion Transfers in Two Polarizable Interface Systems When the Analyte Has Access to Both Interfaces.

A new theory is presented to tackle the study of transfer processes of hydrophilic ions in two polarizable interface systems when the analyte is initially present in both aqueous phases. The treatment is applied to macrointerfaces (linear diffusion) and microholes (highly convergent diffusion), obtaining analytical equations for the current response in any voltammetric technique. The novel equations predict two signals in the current-potential curves that are symmetric when the compositions of the aqueous phases are identical while asymmetries appear otherwise.

Binding studies and anion-selective electrodes with neutral isophthalamide-based receptors.

Two acyclic isophthalamide-based hosts have been synthesised and their anion binding properties have been evaluated by (1)H-NMR titrations. Different binding modes have been detected for the series of tested anions. The attachment of aminomethylpyrrole groups resulted in an improved binding selectivity.

Rubber-based substrates modified with carbon nanotubes inks to build flexible electrochemical sensors.

The development of a solid-contact potentiometric sensor based on conducting rubbers using a carbon nanotubes ink is described here. Commercial rubbers are turned into conductive ones by a simple and versatile method, i.e.

New carbazolo[1,2-a]carbazole derivative as ionophore for anion-selective electrodes: remarkable recognition towards dicarboxylate anions.

A new carbazolo[1,2-a]carbazole derivative was synthesized by expanding the binding cavity to explore the possibility of hosting larger anions such as dicarboxylate anions. The compound was incorporated as an ionophore into a membrane for an anion-selective electrode. The response of the electrode was evaluated for oxalate, malonate, succinate, glutarate and adipate in terms of calibration characteristics (slope, limit of detection and linear range of the response), response time, repeatability, reproducibility and selectivity.

A SO2-selective electrode based on a Zn-porphyrin for wine analysis.

This work describes the assessment of a SO2-selective electrode based on the use of the neutral carrier 5,10,15,20-tetraphenyl(porphyrinate)zinc(II) in a PVC membrane plasticized with 2-nitrophenyl phenyl ether. After being conditioned in 2 mol L(-1) diethylamine solution for 24 h, the electrode exhibited selective anionic response toward the analyte in a concentration interval of more than four decades, with an slope of -59.5 mV dec(-1), a practical detection limit of 3.

New approach for the potentiometric-enzymatic assay of reversible-competitive enzyme inhibitors. Application to acetylcholinesterase inhibitor galantamine and its determination in pharmaceuticals and human urine.

A new kinetic-potentiometric method for the characterization and analytical determination of competitive reversible enzyme inhibitors was developed. The method is based on a mathematical approach, assuming that the reaction proceeds at the steady state, which permits calculation of a tentative substrate concentration to be used to determine low inhibitor concentrations and to obtain the value of inhibition constant corresponding to the inhibitor. The mathematical approach predicts a linear relationship between the inverse of the relative inhibition and the inverse of the inhibitor concentration.

Kinetic effects of the complexation reaction in the facilitated ion transfer at liquid membrane systems of one and two polarized interfaces. Theoretical insights.

An in-depth study of the ion transfer facilitated by complexation in the organic phase (TOC mechanism) in liquid membrane systems of one and two polarized interfaces is carried out by taking into account the kinetic effects associated with the complexation reaction. Explicit analytical equations for the normal pulse voltammetric (I/E) and chronoamperometric (I/t) responses with an explicit dependence on the kinetic parameters of the chemical complexation are presented for both kinds of membrane system, which could be useful for modeling artificial and biological membranes. The equations are compared with those obtained by using the widely used approximation of total equilibrium conditions that leads to the transfer by interfacial complexation mechanism (TIC), which only depends on thermodynamic parameters.

Use of a new ziprasidone-selective electrode in mixed solvents and its application in the analysis of pharmaceuticals and biological fluids.

The construction and characterization of a new ion-selective electrode for the determination of the antipsychotic ziprasidone in mixed solvents is presented. The electrode contains a plasticized polymeric membrane based on a ziprasidone-tetraphenylborate ion-exchanger. The influence of membrane composition on the electrode response towards ziprasidone in hydroalcoholic solutions was studied.

Physical insights of salt transfer through solvent polymeric membranes by means of electrochemical methods.

A combined voltammetric study of the joint transfer of the two constituting ions of a water-soluble salt has been carried out using normal-pulse voltammetry, linear-sweep voltammetry and square-wave voltammetry in a system with two liquid-liquid polarized interfaces. As a result, we have explained the voltammetric features that allow us to distinguish this uptake from that corresponding to two equally charged ions, in spite of the appearance in both situations of two current peaks with the same sign in both square-wave and linear-sweep voltammograms, and we have found that linear-sweep voltammetry and square-wave voltammetry complement each other excellently.A theoretical comparison with a system of a single polarized interface has also been made, showing that these systems are much less appropriate for characterizing these salt-ion transfers.

A retrospective study on outcome of microscopic polyangiitis in chronic renal replacement therapy.

Background: Pauci-immune vasculitis is a heterogeneous disorder with an unfavourable prognosis. Renal involvement is frequently observed in antineutrophil cytoplasm autoantibody (ANCA)-associated small-vessel vasculitis and is an important cause of end-stage renal disease (ESRD). Renal replacement therapy (RRT) is frequently required.

Salvage of accidentally sectioned peritoneal catheter: report of three cases.

Peritoneal dialysis (PD) accounts for 6% of patients on maintenance dialysis. There are several factors responsible for this low prevalence. Transfer of patients to hemodialysis when any problem in the technique is present is probably one of the most frequent reasons.

Achieving chronic kidney disease treatment targets in renal transplant recipients: results from a cross-sectional study in Spain.

Background: Kidney transplant recipients are considered to have chronic kidney disease (CKD) irrespective of glomerular filtration rate (GFR) or presence or absence of markers of kidney damage. The aim of this work was to investigate the prevalence of CKD-stages and whether the guidelines for general population (Kidney Disease Outcomes Quality Initiative) are routinely followed in kidney transplant in Spain.

Patients And Methods: Two thousand one hundred sixty renal transplant recipients followed up at the outpatient clinics in 4 University Hospitals were included.

Application of a trazodone-selective electrode to pharmaceutical quality control and urine analyses.

A trazodone-selective electrode for application in pharmaceutical quality control and urine analysis was developed. The electrode is based on incorporation of a trazodone-tetraphenylborate ion exchanger in a poly(vinyl chloride) membrane. The electrode showed a fast, stable and Nernstian response over a wide trazodone concentration range (5 x 10(-5)-1 x 10(-2) M) with a mean slope of 59.

Very early serum creatinine as a surrogate marker for graft survival beyond 10 years.

Background: Available studies of early serum creatinine (SCr) as a surrogate marker for long-term graft loss are multicenter, registry-based or limited to 5- to 7-year survival.

Methods: This was a single-center observational retrospective study. SCr during the first year post-kidney transplant as an independent variable in determining long-term (>10-year) graft survival in 754 first cadaver kidney transplants was assessed with univariate and multivariate models.

Development of membrane selective electrode for determination of the antipsychotic sulpiride in pharmaceuticals and urine.

The construction and electrochemical response characteristics of a poly(vinyl chloride) (PVC) membrane selective electrode for the determination of sulpiride (SPD) are described. The sensing membrane comprised an ion-exchanger formed between the protonated drug and tetraphenylborate (TPB(-)) in a plasticized PVC matrix. The influence of membrane composition on the electrode response was studied.