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| 19. |
- Grygolowicz-Pawlak, Ewa, et al.
(författare)
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Potentiometric Sensors with Ion-Exchange Donnan Exclusion Membranes
- 2013
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 85:13, s. 6208-6212
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Tidskriftsartikel (refereegranskat)abstract
- Potentiometric sensors that exhibit a non-Hofmeister selectivity sequence are normally designed by selective chemical recognition elements in the membrane. In other situations, when used as detectors in separation science, for example, membranes that respond equally to most ions are preferred. With so-called liquid membranes, a low selectivity is difficult to accomplish since these membranes are intrinsically responsive to lipophilic species. Instead, the high solubility of sample lipids in an ionophore-free sensing matrix results in a deterioration of the response. We explore here potentiometric sensors on the basis of ion-exchange membranes commonly used in fuel cell applications and electrodialysis, which have so far not found their way into the field of ion-selective electrodes. These membranes act as Donnan exclusion membranes as the ions are not stripped of their hydration shell as they interact with the membrane. Because of this, lipophilic ions are no longer preferred over hydrophilic ones, making them promising candidates for the detection of abundant ions in the presence of lipophilic ones or as detectors in separation science. Two types of cation-exchanger membranes and one anion-exchange membrane were characterized, and potentiometric measuring ranges were found to be Nernstian over a wide range down to about 10 μM concentrations. Depending on the specific membrane, lipophilic ions gave equal response to hydrophilic ones or were even somewhat discriminated. The medium and long-term stability and reproducibility of the electrode signals were found to be promising when evaluated in synthetic and whole blood samples.
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| 20. |
- Jansod, Sutida, et al.
(författare)
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Alkalinization of Thin Layer Samples with a Selective Proton Sink Membrane Electrode for Detecting Carbonate by Carbonate-Selective Electrodes
- 2016
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 88:7, s. 3444-3448
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Tidskriftsartikel (refereegranskat)abstract
- Potentiometry is known to be sensitive to so-called free ion activity and is a potentially valuable tool in environmental speciation analysis. Here, the direct detection of free and total carbonate is demonstrated by alkalinization of a thin layer sample (∼100 μm), which is electrochemically triggered at a pH responsive membrane placed opposite a carbonate-selective membrane electrode. The concept may serve as a promising future methodology for in situ environmental sensing applications where traditional sampling and pretreatment steps are no longer required. The possibility of increasing the pH of the sample was demonstrated first with a proton selective membrane (pH readout at zero current) placed opposite the thin layer gap. An optimal applied potential (600 mV) for 300 s resulted in a pH increase of 4 units in an artificial sample, with a relative standard deviation (RSD) of ∼2%. The pH probe was subsequently replaced by a solid contact carbonate selective electrode for the determination of carbonate species (4.17 μM) in a sample of 1 mM NaHCO3. Increasing the pH to 12.1 by the electrochemically controlled proton sink allowed one to convert bicarbonate to the detectable carbonate species. Initial bicarbonate concentration (∼1 mM) was obtained as the difference between the converted bicarbonate and the initial carbonate concentration. An initial application of this concept was illustrated by the speciation analysis of an unfiltered sample from the Arve river (12.3 ± 0.2 μM and 22.5 ± 0.3 mM carbonate and bicarbonate, respectively). The values were confirmed by volumetric titration.
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| 21. |
- Jansod, Sutida, et al.
(författare)
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Phenytoin speciation with potentiometric and chronopotentiometric ion-selective membrane electrodes
- 2016
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Ingår i: Biosensors & bioelectronics. - : Elsevier. - 0956-5663 .- 1873-4235. ; 79, s. 114-120
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Tidskriftsartikel (refereegranskat)abstract
- We report on an electrochemical protocol based on perm-selective membranes to provide valuable information about the speciation of ionizable drugs, with phenytoin as a model example. Membranes containing varying amounts of tetradodecylammonium chloride (TDDA) were read out at zero current (potentiometry) and with applied current techniques (chronopotentiometry). Potentiometry allows one to assess the ionized form of phenytoin (pKa~8.2) that corresponds to a negatively monocharged ion. A careful optimization of the membrane components resulted in a lower limit of detection (~1.6 µM) than previous reports. Once the pH (from 9 to 10) or the concentration of albumin is varied in the sample (from 0 to 30 g L−1), the potentiometric signal changes abruptly as a result of reducing/increasing the ionized concentration of phenytoin. Therefore, potentiometry as a single technique is by itself not sufficient to obtain information about the concentration and speciation of the drug in the system. For this reason, a tandem configuration with chronopotentiometry as additional readout principle was used to determine the total and ionized concentration of phenytoin. In samples containing excess albumin the rate-limiting step for the chronopotentiometry readout appears to be the diffusion of ionized phenytoin preceded by comparatively rapid deprotonation and decomplexation reactions. This protocol was applied to measure phenytoin in pharmaceutical tables (100 mg per tablet). This tandem approach can likely be extended to more ionizable drugs and may eventually be utilized in view of pharmacological monitoring of drugs during the delivery process.
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| 22. |
- Jarolimova, Zdenka, et al.
(författare)
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All solid state chronopotentiometric ion-selective electrodes based on ferrocene functionalized PVC
- 2013
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Ingår i: Journal of Electroanalytical Chemistry. - : Elsevier. - 0022-0728 .- 1873-2569 .- 1572-6657. ; 709, s. 118-125
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Tidskriftsartikel (refereegranskat)abstract
- An all solid contact ion-selective electrode based on poly(vinyl chloride) covalently modified with ferrocene moieties allows one to operate the membrane in a chronopotentiometric sensing mode. The membrane is considered as initially non-perm-selective towards anions, and an applied anodic current provokes a defined anion flux in direction of the membrane. With this protocol, a variety of anions can be depleted at the membrane surface. Since this model system does not yet contain an ionophore, their order of preference follows the expected Hofmeister selectivity sequence. The all solid-state configuration tolerates an imposed current density of 1.4 μA mm−2, which translates into an upper detection limit of ca. 1.2 mM. Higher current densities of up to 31.2 μA mm−2are possible with addition of freely dissolved alkyl ferrocene derivative for an expected upper detection limit of 17.0 mM. Numerical simulations are performed in order to establish the fundamental basis of the mechanism that takes place in this all solid-state membrane electrode. The oxidation of bound Fc and the ion-transfer process are considered in the simulation. In view of developing an analytical sensor, different anions are tested. A linear range of two orders of magnitude from 0.01 to 1 mM is found. The membranes are evaluated over several days, displaying practically the same slopes and intercepts, with a RSD of less than 2%. Electrochemical limitations of free Fc and bound Fc are critical evaluated. This approach should allow one to develop a new family of solid-state chronopotentiometric ion sensors that require relatively high current densities.
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| 23. |
- Jarolimova, Zdenka, et al.
(författare)
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Chronopotentiometric Carbonate Detection with All-Solid-State lonophore-Based Electrodes
- 2014
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 86:13, s. 6307-6314
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Tidskriftsartikel (refereegranskat)abstract
- We present here for the first time an all-solid-state chronopotentiometric ion sensing system based on selective ionophores, specifically for the carbonate anion. A chronopotentiometric readout is attractive because it may allow one to obtain complementary information on the sample speciation compared to zero-current potentiometry and detect the sum of labile carbonate species instead of only ion activity. Ferrocene covalently attached to the PVC polymeric chain acts as an ion-to-electron transducer and provides the driving force to initiate the sensing process at the membrane–sample interface. The incorporation of a selective ionophore for carbonate allows one to determine this anion in a background electrolyte. Various inner electrolyte and all-solid-state-membrane configurations are explored, and localized carbonate depletion is only observed for systems that do not contain ion-exchanger additives. The square root of the transition times extracted from the inflection point of the chronopotentiograms as a function of carbonate specie concentration follows a linear relationship. The observed linear range is 0.03–0.35 mM in a pH range of 9.50–10.05. By applying the Sand equation, the diffusion coefficient of carbonate is calculated as (9.03 ± 0.91) 10–6 cm2 s–1, which corresponds to the established value. The reproducibility of assessed carbonate is better than 1%. Additionally, carbonate is monitored during titrimetric analysis as a precursor to an in situ environmental determination. Based on these results, Fc-PVC membranes doped with ionophores may form the basis of a new family of passive/active all-solid-state ion selective electrodes interrogated by a current pulse.
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| 24. |
- Jeanneret, Stephane, et al.
(författare)
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GalvaPot, a custom-made combination galvanostat/potentiostat and high impedance potentiometer for decentralized measurements of ionophore-based electrodes
- 2015
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier. - 0925-4005 .- 1873-3077. ; 207, s. 631-639
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Tidskriftsartikel (refereegranskat)abstract
- We report here on a portable, custom-made instrument for decentralized measurements with ionophore based electrodes. It allows one to perform most common electrochemical protocols based on applied current or potential as well as zero current potentiometry measurements. Each protocol is customizable via a programmable interface by use of either an external PC or a touch screen panel on the device. The programmable interface provides flexibility to trigger peripheral devices for the additional implementation of actuators, pumps and other external devices in the electrochemical routines.To characterize the electronic performance of the instrument, three different electrochemical protocols were used with ionophore based electrodes and compared with a commercial work station: (1) open circuit potentiometric measurements with calcium ion-selective membranes; (2) chronoamperometry based on three successive pulses with simultaneous control of fluidic delivery by a peristaltic pump and switching valve, followed by on board current integration to obtain a coulometric readout; (3) a chronopotentiometric protocol using protamine selective membranes with current pulses of 5-s duration, including an automatic computation of the time-derivative to find the transition time as the analytical signal. At 500 g, the instrument is portable yet sufficiently versatile for performing and analyzing most electrochemical measurements without the need for an external computer. It may become an attractive tool for applications in environmental and clinical analysis where field portability, flexibility and integration are desired.
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| 25. |
- Mokhlesi, Babak, et al.
(författare)
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The Effect of Hospital Discharge with Empiric Noninvasive Ventilation on Mortality in Hospitalized Patients with Obesity Hypoventilation Syndrome An Individual Patient Data Meta-Analysis
- 2020
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Ingår i: Proceedings of the American Thoracic Society online. - : American Thoracic Society. - 1546-3222 .- 1943-5665. ; 17:5, s. 627-637
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Forskningsöversikt (refereegranskat)abstract
- Rationale: Hospitalized patients with acute-on-chronic hypercapnic respiratory failure due to obesity hypoventilation syndrome (OHS) have increased short-term mortality. It is unknown whether prescribing empiric positive airway pressure (PAP) at the time of hospital discharge reduces mortality compared with waiting for an outpatient evaluation (i.e., outpatient sleep study and outpatient PAP titration).Objectives: An international, multidisciplinary panel of experts developed clinical practice guidelines on OHS for the American Thoracic Society. The guideline panel asked whether hospitalized adult patients with acute-on-chronic hypercapnic respiratory failure suspected of having OHS, in whom the diagnosis has not yet been made, should be discharged from the hospital with or without empiric PAP treatment until the diagnosis of OHS is either confirmed or ruled out.Methods: A systematic review with individual patient data meta-analyses was performed to inform the guideline panel’s recommendation. Grading of Recommendations, Assessment, Development, and Evaluation was used to summarize evidence and appraise quality.Results: The literature search identified 2,994 articles. There were no randomized trials. Ten studies met a priori study selection criteria, including two nonrandomized comparative studies and eight nonrandomized noncomparative studies. Individual patient data on hospitalized patients who survived to hospital discharge were obtained from nine of the studies and included a total of 1,162 patients (1,043 discharged with PAP and 119 discharged without PAP). Empiric noninvasive ventilation was prescribed in 91.5% of patients discharged on PAP, and the remainder received empiric continuous PAP. Discharge with PAP reduced mortality at 3 months (relative risk 0.12, 95% confidence interval 0.05–0.30, risk difference −14.5%). Certainty in the estimated effects was very low.Conclusions: Hospital discharge with PAP reduces mortality following acute-on-chronic hypercapnic respiratory failure in patients with OHS or suspected of having OHS. Well-designed clinical trials are needed to confirm this finding.
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| 26. |
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| 27. |
- Pankratova, Nadezda, et al.
(författare)
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Potentiometric sensing array for monitoring aquatic systems
- 2015
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Ingår i: Environmental Science. - : Royal Society of Chemistry (RSC). - 2050-7887 .- 2050-7895. ; 17:5, s. 906-914
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Tidskriftsartikel (refereegranskat)abstract
- Since aquatic environments are highly heterogeneous and dynamic, there is the need in aquatic ecosystem monitoring to replace traditional approaches based on periodical sampling followed by laboratory analysis with new automated techniques that allow one to obtain monitoring data with high spatial and temporal resolution. We report here on a potentiometric sensing array based on polymeric membrane materials for the continuous monitoring of nutrients and chemical species relevant for the carbon cycle in freshwater ecosystems. The proposed setup operates autonomously, with measurement, calibration, fluidic control and acquisition triggers all integrated into a self-contained instrument. Experimental validation was performed on an automated monitoring platform on lake Greifensee (Switzerland) using potentiometric sensors selective for hydrogen ions, carbonate, calcium, nitrate and ammonium. Results from the field tests were compared with those obtained by traditional laboratory analysis. A linear correlation between calcium and nitrate activities measured with ISEs and relevant concentrations measured in the laboratory was found, with the slopes corresponding to apparent single ion activity coefficients and. Good correlation between pH values measured with ISE and CTD probes (SD = 0.2 pH) suggests adequate reliability of the methodology.
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