Response Time Of Electrode Research Articles

Comparison of microbial sensors based on amperometric and potentiometric electrodes

Microbial sensors based on oxygenn and carbon dioxide electrodes coupled with immobilized Saccharomyces are compared for measurements of glucose and other carbohydrates. With the oxygen sensor, the yeast works under aerobic conditions but anaerobically with the carbon dioxide sensor. The two metabolisms of the same strain make little difference to the lifetimes (> 15 days), selectivities and response rates (5–10 min) of the sensors. The effects of pH are very different owing to the pH sensitivity of the carbon dioxide sensor. The viable concentration ranges overlap; the oxygen-based sensor is more useful for low concentrations of glucose (0.01–1 mmol l −1) while the carbon dioxide-based sensor is better suited for 1–10 mmol l −1. With the oxygen-based sensor, the response time is governed by the rate of metabolism; with the carbon dioxide-based sensor, the response time of the potentiometric carbon dioxide electrode is the rate determining step.

The Preparation and Properties of the Manganese(II) Ion-Selective Electrode

Abstract For the measurement of manganese(II)-ion activity, manganese(II) ion-selective electrodes were prepared and tested. As electrodes, heterogeneous membranes were prepared by dispersing sensitive materials, such as manganese sulfide, manganese borate, or manganese dibenzyldithiocarbamate, in silicone rubber, poly(vinyl chloride), or poly(vinyl acetate). A manganese chloride solution (0.1 mol dm−3) was used as the internal reference solution, along with an Ag/AgCl internal reference electrode. The manganese(II) ion-selective electrodes thus made were then examined in terms of their response curves, response times, the effect of the pH, the variation in the response slopes with the temperature, and selectivity coefficients. The response time of the manganese dibenzyldithiocarbamate electrode was within 15 s in the concentration range of 10−8–10−1 mol dm−3. The response slope was 33.14 mV/pMn2+ in the linear part, and the coefficient of correlation was 0.999. The selectivity coefficients were examined by the separate-solution method.

Definition and determination of response time of ion selective electrodes

Abstract

Electrode and cuvette for rapid continuous CO2 tension and pH measurement in blood

An electrode and cuvette system has been developed for the continuous and rapid measurement of either blood CO2 tension or pH. The CO2 electrode consists of a 1.5-mm-diameter flat-tip glass pH electrode covered by a film of carbonic anhydrase solution, over which a 25-micron-thick dimethyl silicone membrane is attached. Porous ceramic filled with 20% polyacrylamide, equilibrated with a salt solution, serves as a salt bridge between a Ag-AgCl reference electrode and the pH electrode surface. The electrode is housed in a four-port cuvette assembly. Blood from a vessel of interest is delivered to the cuvette by means of an occlusive roller pump. The cuvette maintains the electrode and blood at a constant temperature and directs a continuous jet of blood against the electrode surface. The cuvette also allows for easy and frequent calibration of the electrode with either gas or liquid standards. The 90% response time of the CO2 electrode is 3.0 s for liquids and 1.3 s for gases. Removal of the dimethyl silicone membrane and carbonic anhydrase film yields a pH electrode that can continuously measure blood pH with a 90% response time of 1.6 s.

The glass electrode — applied electrochemistry of glass surfaces

The glass electrode has attained a high standard of construction and application during the almost eighty years of development. The understanding of its functioning, however, has been much slower, and its history represents an example of highly advanced thermodynamics rather than of applied electrochemistry of glass surfaces. Thus, the generally accepted, purely thermodynamic, ion exchange theory cannot give any information about the ionic mechanism of potential formation. From detailed information on glass surfaces by modern surface-analytical methods we have recenttly concluded a “dissociation mechanism”, which is based on the equilibria of functional groups at the glass surface and ions in contacting solutions. This mechanism and several phenomena at the glass surface are described on the basis of electrode kinetics in this paper, and it is proposed to develop methods of measuring kinetic data, e.g. equilibrium exchange current densities of protons and alkali ions between the glass surface groups and the solution. These data, if availbale and in connection with information from other surface-analytical methods, could prove the ionic equilibria at the glass—solution-interface and thus state the dissociation mechanism, elucidate unanswered questions, e.g. the cause of the response time of glass electrodes, and also contribute to the investigation of the fundamental processes of glass corrosion.

Calibration and use of a Clark-type oxygen electrode from 5 to 45°C

A calibration procedure for a Clark-type oxygen electrode over a wide range of temperatures is described. The autoxidation of duroquinol (2,3,5,6-tetramethyl-1,4-benzenediol) was used to verify the electrode's ability to accurately sense the total amount of dissolved O 2 in an aqueous buffer. Electrode response time was measured by using oxygenated ethanol to deliver a rapid increase in O 2 concentration to the reaction medium. An oxygen-producing system (spinach thylakoids) was utilized to test the range of O 2-evolution rates able to be sensed. It was concluded that a Clark-type oxygen electrode has the absolute sensitivity, rapidity, and range necessary to accurately track rates of O 2 production or consumption from 5 to 45°C.

Novel ion-selective electrode system for the simultaneous determination of fluoride and calcium in acid solution.

A method is described that utilises two independent electrode systems; a new ultra-sensitive fluoride-glass pH electrode differential cell and a calcium electrode monitor for the direct and simultaneous measurement of both fluoride and calcium in unbuffered acid solution. Fluoride Nernstian response may be extended by at least one decade towards the lower limit of detection, with an appreciable reduction in electrode response time at low concentrations when compared with the conventional use of fluoride electrodes using TISAB-type buffers. The system has been successfully applied as a biopsy technique for the determination of fluoride concentration profiles within the outer 100 µm of human tooth enamel.

Photomicrobial electrode for selective determination of sulphide

A photomicrobial electrode, which uses the photosynthetic bacteria Chromatium sp. in conjunction with a hydrogen electrode, was developed for the determination of sulphide. The response time of the photomicrobial electrode was 5–10 min. A linear relationship was obtained between the current of the electrode and the sodium sulphide concentration below 3.5 mM. The minimum detectable concentration of sodium sulphide was 0.4 mM. Selectivity of the sensor is satisfactory. A good agreement was obtained between the photomicrobial electrode and the ethylene blue method (correlation coefficient: 0.90).

Energetics of isometric contraction in porcine carotid artery.

The rate of ATP utilization ( JATP ) and unloaded shortening velocity ( Vus ) of porcine carotid artery were studied during tension development and maintenance to assess the importance of mechanisms proposed to account for its high economy of tension maintenance. Previous work from our laboratory established that the rate of O2 consumption ( JO2 ) can be used to measure rates of tissue phosphagen utilization as early as 30 s after initiation of contraction. Studies at 37 degrees C of tissue JO2 indicated the following. 1) The basal JO2 was 0.069 +/- 0.017 mumol O2 X min-1 X g-1) (n = 10). During steady-state tension maintenance suprabasal JO2 was 0.079 +/- 0.012 mumol O2 X min-1 X g-1 for tissues stimulated with KCl (n = 11) and 0.213 +/- 0.022 (n = 3) for tissues stimulated with KCl + histamine. 2) For both stimulation conditions an initial elevated (peak) suprabasal JO2 was observed that correlated with the rate of tension development. The peak suprabasal JO2 was approximately twice the steady-state suprabasal JO2 measured 10 min after stimulation. 3) There was no significant change in JO2 during tension redevelopment after a rapid length step at 15-20 min after stimulation (n = 4). Studies of Vus indicated the following. 1) During steady-state tension maintenance Vus was 0.008 +/- 0.001 tissue lengths/s for tissues stimulated with KCl (n = 13) tissue lengths/s for tissues stimulated with KCl + histamine (n = 6). 2) An initial twofold peak in Vus was observed at 0.25-0.5 min in that decreased to steady-state levels by 4 min after KCl stimulation, whereas minor decreases in Vus still occurred until 10-20 min after KCl + histamine stimulation. 3) The measured transient in Vus , although biphasic, does not temporally correlate with the transient in JO2 even after the JO2 time course was corrected for delays resulting from O2 diffusion and the electrode response time. The mechanism underlying the observed maximum change of two- to fourfold in both JATP and Vus is not sufficient to account for the high economy of tension maintenance.

Definition of the response time of ion-selective electrodes and potentiometric cells

Definition of the response time of ion-selective electrodes and potentiometric cells

An enzyme electrode for determination of aromatic diamines and aminophenols based on cross-linked ceruloplasmin

The determination of aromatic amines and phenols by an enzyme pO2 electrode containing cross-linked ceruloplasmin in the reaction layer was examined. The electrode shows at pH 5.5 a marked selectivity for derivatives with-NH2 or NR2, resp., and -OH-groups in para and ortho position while its sensitivity for aromatic diamines is better than its sensitivity for aminophenols and polyphenols. p-Phenylenediamine and its N,N-dialkyl derivatives are the best analytes which can be detected starting from concentrations of 10-5 mol l-1 and higher; the reproducibility is 5-7% at an electrode response time of 2-5 min.

Effect of storage solution composition on pH combination electrode response times at low temperature

Download options Please wait... Article information DOI https://doi.org/10.1039/AN9840901225 Article type Paper Download Citation Analyst, 1984,109, 1225-1226 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Effect of storage solution composition on pH combination electrode response times at low temperature R. C. Metcalf, Analyst, 1984, 109, 1225 DOI: 10.1039/AN9840901225 To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Social activity Tweet Share Search articles by author Richard C. Metcalf

Bipolar pulse conductometric monitoring of ion-selective electrodes : Part 3. Studies with the calcium and fluoride electrodes in a continuous flow system

Bipolar pulse conductometric monitoring of the calcium and fluoride ion-selective electrodes (i.s.e.'s) in a continuous flow system is evaluated. The location and composition of the counter electrode are critical; an electrochemically poised reference electrode is not necessary. The best scheme for conductometric measurements involves making a rapid series of current measurements at various pulse heights, and extrapolating the resulting linear current—voltage (i/ V) curve to V = 0. For ionic strengths higher than 10 −3 M, detection limits of about 10 −6 M were obtained with both the calcium and fluoride electrodes, monitored conductometrically and potentiometrically. Relative standard deviations were about 20% and 12% for calcium and fluoride, respectively, for both monitoring methods. Drift problems observed in previous work with conductometric monitoring of i.s.e.'s were reduced significantly. Flow rates of 20 ml min −1 were possible with the calcium electrode. The response time of the calcium electrode is influenced by both diffusion and migration processes. Interfering ions cause the current to overshoot the steady-state current on injection. The conductometric response time of the fluoride electrode is generally faster than the potentiometric response time; both methods have concentration-dependent response times.

The Ternary Coppersilver Selenide—A New Homogeneous Solid State Ion-Selective Electrode for Copper (II)

Abstract The performance characteristics of a copper (II) ion-selective electrode, based on pressed-pellet membrane of ternary CuAgSe, are reported. The sensing material is isostructural with the natural mineral β -eucairite and shows high corrosion resistivity which results in stable and reproducible electrode performance upon ageing. The electrodes exhibit a linear Nernstian response dawn to 5.10−8 M in non buffered medium and down to 10−13M in copper-glycine ion buffer. Data on the electrode stability for a period of two and a half years, on the electrode response time, pH-dependence, selectivity etc. are also presented.

Flow injection analysis system for determining soil pH

A flow injection analysis system is described for the determination of soil pH in filtered 0.01 M calcium chloride solution extracts. The system is constructed entirely from off-the-shelf components and is capable of analysing up to 90 samples in 1 h. The unbuffered nature of filtered soil extracts causes problems in terms of electrode response times and imposes restrictions on the composition of the carrier-stream buffer and reference standards.

Investigation of some new solid cation exchange membrane electrodes for activity determination of mono-valent cations

Solid cation exchange membrane electrodes prepared by incorporating weak cation exchangers stilbite, bentonite clay and ammonium phosphomolybdate in cellulose nitrate inert matrix, have been characterized by determination of their thermodynamic effective charge densities. Null potentiometry method has been used for the determination of activities of Na +, K + and NH + 4 cations in their chloride solutions separately and in the mixture of two cations using these electrodes. The selectivity of these electrodes for cations has been interpreted on the basis of Thermodynamic effective charge density of the membrane electrode and the results have been confirmed by determining the selectivity coefficients of these electrodes for the investigated cations by an IUPAC method. The error in the determination of activities of cations and response time ( t/min) of electrode have been correlated with the thermodynamic effective charge density of the electrode. It has been found that the electrodes with low thermodynamic effective charge density are more suitable for this purpose and that selectivity of an electrode for a particular cation in mixture depends upon the characteristics of both cation and electrode.

Compensation for measuring error produced by finite response time in determination of rates of oxygen consumption with a Clark-type polarographic electrode

In the determination of the rates of oxygen consumption with a Clark-type oxygen electrode, and experimental error is caused by finite response time of the oxygen electrode for a rapid oxidation reaction. A theoretical equation between the observed pseudo first-order rate constant ( k obs) and the true rate constant ( k) 1 k obs = 1 k +T where T is a time constant for a first-order response of the oxygen electrode, was derived and found to hold up to k = 23 min −1 in oxidation of hydroquinone at pH 7.60–8.63.

Unpredictable fluctuations in transcutaneous pCO2 from capillary blood gas determinations.

Transcutaneous pCO2 electrode response time was optimized by use of a new electrode filling solution composed of NaCl/NaHCO3 electrolyte buffer (100 and 20 mmol/L, respectively) in an equivolume mixture of glycerol and water. The 95% response time to a step change in pCO2 was 49.9 +/- 2.8 s (mean +/- SD) when there was no spacer between the membrane and glass of the electrode. Use of this filling solution during monitoring of severely ill premature infants with cardiopulmonary disease allowed identification of large, unpredictable transient changes in transcutaneous pCO2, and therefore presumably in arterial pCO2, that occurred during capillary blood gas sampling. The changes, which occurred in 19 of 20 samplings, ranged from -1.06 + 2.53 kPa (-8 to +19 Torr). The maximum relative change observed was +29%. These results indicate that the standard protocol for capillary blood collection induces significant transient fluctuations in blood gas tensions. We believe these fluctuations decrease the reliability of capillary pCO2 values for use in clinical management in patient populations similar to ours.

Role of the diffusion process on the response time of CO 2 electrodes

An equation was derived to compute the response time of any potentiometric electrode consisting of an inert membrane, an internal solution and a potentiometric sensor. This equation was tested with the CO 2 electrode. The influence of the membrane thickness was studied in particular, and the diffusion coefficient of CO 2 through DuPont de Nemours “Teflon” FEP membranes was determined. Permeabilities of CO 2 and water through these membranes were also measured by other methods. The influence of various factors on the response time of the CO 2 electrode has been discussed.

Evaluation of response time of a transcutaneous oxygen tension electrode.

Response characteristics of a transcutaneous PO2 electrode to step changes in PaO2 were determined. In vitro lag time and 95% response time of a transcutaneous PO2 monitor were compared to in vivo response. Release of arterial occlusion was used to produce rapid local PaO2 changes in human infants and adults. In vitro lag time and 95% response time varied according to whether an increment or decrement in PO2 was produced. In vivo 95% response time of this electrode was two to six times slower than previous estimates, and it varied significantly with the magnitude of the step change, subject age, anatomic location, and local hemodynamic factors. Also, we found that in vivo lag time is two to three times faster than previously reported.