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PubMed1983

Influence of erythrocytes on direct potentiometric determination of sodium and potassium.

We have shown that the sodium concentration in whole blood measured by direct potentiometry is higher than in plasma. The 'erythrocyte-effect', already described by Siggaard Andersen, is most pronounced for instruments equipped with a reference electrode with an open static liquid junction and is thus a general phenomenon. Instruments with a modified liquid junction show less interference. The same phenomenon appears for the determination of the potassium concentration, although the difference between whole blood and plasma, when measured with instruments equipped with a modified liquid junction, can be neglected in practice.

Erythrocytes↗
PubMed2006

In-vitro study on the competitive binding of diflunisal and uraemic toxins to serum albumin and human plasma using a potentiometric ion-probe technique.

The competitive binding of diflunisal and three well-known uraemic toxins (3-indoxyl sulfate, indole-3-acetic acid and hippuric acid) to bovine serum albumin (BSA), human serum albumin (HSA) and human plasma was studied by direct potentiometry. The method used the potentiometric drug ion-probe technique with a home-made ion sensor (electrode) selective to the drug anion. The site-oriented Scatchard model was used to describe the binding of diflunisal to BSA, HSA and human plasma, while the general competitive binding model was used to calculate the binding parameters of the three uraemic toxins to BSA. Diflunisal binding parameters, number of binding sites, n(i) and association constants for each class of binding site, K(i), were calculated in the absence and presence of uraemic toxins. Although diflunisal exhibits high binding affinity for site I of HSA and the three uraemic toxins bind primarily to site II, strong interaction was observed between the drug and the three toxins, which were found to affect the binding of diflunisal on its primary class of binding sites on both BSA and HSA molecules and on human plasma. These results are strong evidence that the decreased binding of diflunisal that occurs in uraemic plasma may not be solely attributed to the lower albumin concentration observed in many patients with renal failure. The uraemic toxins that accumulate in uraemic plasma may displace the drug from its specific binding sites on plasma proteins, resulting in increased free drug plasma concentration in uraemic patients.

Algorithms↗
PubMed1993

A widely applicable electrode sensitive to basic drugs based on poly(vinyl chloride) membrane plasticized with tricresyl phosphate.

A plastic membrane ion-selective electrode applicable to many basic drugs has been developed. The electrode developed was constructed with tricresyl phosphate and a poly(vinyl chloride) matrix on a polytetrafluoroethylene film. The electrode showed a near-Nernstian response to chlorpromazine, trihexyphenidyl, imipramine, dibucaine, papaverine, propranolol, tetracaine, trazodone, quinidine and cinnarizine. The determination of 50 to 3000 micrograms/ml of trazodone hydrochloride in a pH 4.0 acetate buffer solution showed an average recovery of 99.4% (mean standard deviation 0.7%) by direct potentiometry. Inorganic cations and pharmaceutical excipients did not interfere with the determination. Trazodone hydrochloride and trihexyphenidyl hydrochloride in tablets were determined, and the results compared favorably with those obtained by conventional methods.

Anesthetics, Local↗
PubMed2006

Comparison of vitros dry slide technology for determination of lithium ions with other methods.

The lithium ions concentration in human serum was determined using Dry-slide technology Vitros 250 Analyser (Ortho Clinical Diagnostic), atomic absorption spectrometry (AAS) method Perkin Elmer 403 and ion-selective electrode (ISE) potentiometry AVL 9181. We compared lithium ions results in sample sera between these methods. Our reference method was AAS. We analyzed lithium ions concentration in 23 sera samples of patients after oral administration of lithium carbonate (3x 300mg) Jadran, Galen Laboratory Rijeka, by dry-slide technology, AAS and ISE methods. The quality control, precision, reproducibility and accuracy for Vitros dry slide technology were assessed. We established that the main difference between AAS method and dry slide technology was not statistically significant at p< 0.05 according to Student t-test. Therefore, the dry slide technology may be a useful alternative or it may even replace other methods, such as AAS. The main difference between dry slide technology and ISE methods was statistically significant at p<0.05 using Student t-test. By ISE method, we obtained considerably higher results, which may be explained by the presence of electrolytes or medicaments interfering with lithium ions.

Adult↗
PubMed2005

Membrane sensors for the selective determination of thiopental.

Novel miniaturized polyurethane (PU) membrane sensors in an all-solid state graphite support were developed, electrochemically evaluated and used for the assay of thiopental drug. The thiopental (T) sensors are based on the formation of ion-association complexes of thiopental with copper(II) and cobalt(II)-bathophenanthroline (bphen) counter anions as electroactive materials dispersed in a polyurethane matrix. The sensors show a linear response for thiopental over the range of 1 x 10(-1) - 5 x 10(-5) M thiopental at 25 degrees C over the pH range 6 - 11 with anionic slopes of -28.7 and -28.3 mV decade(-1) with Cu- and Co-bphen thiopental membrane sensors, respectively. These sensors exhibit a fast response time (25 - 45 s), a low detection limit (5 x 10(-6) M), a long lifetime (7 weeks) and good stability. The selectivity coefficients for thiopental sensors relative to the number of interfering anions, were investigated. These sensors were used for the direct potentiometry of thiopental in a pharmaceutical formulation and human serum. Results with mean accuracy of 99.8 +/- 0.5% of nominal were obtained, which compare well with data obtained using spectrophotometric (UV-Vis) and British Pharmacopoeia (BP) methods.

Humans↗
PubMed1979

The calcium selective electrode--a possible tool in dental research.

Ion selective potentiometry is widely used for analytical purposes in biologic research. The Ca selective electrode offers an inexpensive and easily handled means for studying ionized calcium. It does not affect the process studied, and may, for example, combined with an automatic recorder, give running information on dynamic systems. The calcium electrode responds in accordance with the Nernst equation and has a theoretical range of 1--10(-6) M Ca2+. The electrode is influenced by changes in temperature, in pH and also in concentration of buffer solution. The Ca sensitive membrane is adversely affected by acetic acid but tolerates lactate/lactic acid buffers. Best linearity in calibration curves for Ca2+ in lactate buffers is found in concentrations from 10(-4) M to 10(-2) M Ca. In a 5% Na lactate/lactic acid buffer, pH 5, with 0.5 M KNO3 as an ionic strength adjuster, a straight calibration curve, Nernstian slope factor 27 mV/decade, is found from 10(-4) to 1 M Ca.

Buffers↗
PubMed1989

Potentiometric (bioselective electrodes) assay systems: utility and limitations.

Numerous potentiometric assays utilizing bioselective electrodes are fast revolutionizing many areas of biotechnology. Adequately discussing the utility and limitations of these electrochemical systems is the purpose of this review. A general overview introduces bioselective potentiometry by presenting basic concepts, historical background, and current developments. Essentially, the review consists of several sections describing electrode architecture, operational concepts, different biosensors, assay systems, applications, and future trends. Advantages and disadvantages of the different bioselective assay systems discussed are included throughout each section. Electrode design discussion covers conventional liquid probes and the newer solid-state transitor biosensors. Limitations and advantages of different chemoreceptors, biocatalysts, and potentiometric transducers are presented. Operational characteristics include: linear behavior, sensitivity, stability, specificity, response, recovery, and the influence of interfering factors. Enzyme, organelle, tissue, and microbial biocatalytic sensors are discussed. Bioligand systems include: affinity, immunoselective enzyme, and liposome sensors. Potentiometric bioselective drug, microbial, and immunoassay systems are also included.

Electrodes↗
PubMedDate not supplied

[Ion-selective electrodes with a liquid membrane for determining N-butylscopolammonium bromide].

Two ion-selective electrodes with liquid membrane for N-butylscopolamonium bromide are described, with N-butylscopolamonium tetraphenylborate (I) and N-butylscopolamonium reineckate (II), respectively, solved in benzylic alcohol as electroactive material. These electrodes have a linear response in the concentration range of 10(-2)-10(-6) M N-butylscopolamonium bromide, with the detection limit of 10(-7) M for both electrodes. These electrodes were used with good results for quantitative assay by direct potentiometry of injectable solutions of N-butylscopolamonium bromide.

Butylscopolammonium Bromide↗
PubMed2003

On the complex formation equilibria between dioxouranium(VI) and sulfate ions.

The complexation equilibria between UO2(2+) and SO4(2-) ions have been studied at 25 degrees C in the ionic medium 3 M NaClO4 by potentiometry, by spectrophotometry and by solubility measurements of UO2(IO3)2. The potentiometric investigation was carried out with the Hg-Hg2SO4(s)-SO4(2-) half-cell and glass electrode in the sulfate concentration range 0.005 to 0.07 M. The optical absorbances in the UV-visible region and the solubility data cover the ligand concentration range 0.005 to 0.3 M. The data could be explained by assuming the complexes and equilibrium constants [Table: see text]. The constants in the infinite dilution reference state, log beta1o = 3.08 +/- 0.15 and log beta2o = 4.28 +/- 0.15, estimated by assuming the validity of the specific interaction theory, are practically coincident with literature data.

Numerical Analysis, Computer-Assisted↗
PubMedDate not supplied

[Membrane-selective electrode for atropine assay].

One membrane-selective electrode with PVC matrix for atropine is described, with atropine tetraphenylborate as electroactive material. This electrode has a linear response in the concentration range of 10(-2)-10(-5) M atropine sulphate, with a detection limit of 3.29 x 10(-6) M. This electrode was used with good results for quantitative assay by direct potentiometry and potentiometric titration of atropine sulphate from pharmaceutical formulations.

Algorithms↗
PubMedDate not supplied

Differential electrolytic potentiometric determination of some amino acids in dosage forms.

The application of direct-current differential electrolytic potentiometry to the nonaqueous titration of amino acids was investigated. The basic character of amino acids in acetic acid was enhanced to permit their direct titration with perchloric acid. A pair of antimony electrodes was used as an indicating system. The shapes of the titration curves obtained were almost symmetrical with sharp peaks. The optimum current density for those titrations was found to be 1-2 microA/cm2. The procedure was applied successfully to the determination of certain amino acids in drug formulations, and the results were favorably compared statistically with those obtained by official methods.

Amino Acids↗
PubMed2004

Assessment of potassium and sodium ion concentrations in the vitreous humour of swine isolated eyeballs after organism death.

Potassium and sodium ion concentrations were estimated by the flame photometry and potentiometry in the vitreous fluid of isolated porcine eyeballs at time of death and of eyeballs, stored at temperature of 6-8 degrees C during post-mortem intervals: 4, 28, 52, 75, 100, 124 and 148 hours. The increase of K+ concentration and decrease of Na+ concentration were proportional to the increasing post-mortem time intervals. The results of the potentiometric measurements of K+ and sodium ion concentrations were significantly lower, as compared to those after flame photometry. In all the vitreous fluid smears after 124 and 148 hours, gram (-) bacteria were found. Our results suggest that bacterial infection participates in the variability of K+ levels. The influence of bacterial infection on the margin of error for the K+ post-mortem test remains unanswered and needs further studies.

Animals↗
PubMedDate not supplied

[R-phycoerythrin: a natural ligand for detoxifying cadmium ions and a tunnel matrix for synthesis of cadmium sulfide nanoparticles].

As evidenced by ion-selective electrode potentiometry, the hexameric R-phycoerythrin (RPE) molecule binds 20-4000 cadmium ions (Cd2+) depending on Cd2+ concentration in the solution. Cadmium ions bound to RPE serve as nuclei of cadmium sulfide crystallization in the presence of sulfide ions. According to spectrometric, electron-microscopic and capillary electrophoresis data, the particles are heteroaggregates of 3.2 x 6 nm in size. The fact that the particle size fits the size of the central tunnel of the RPE molecule and the similarity between the electrophoretic patterns of free RPE and the RPE-CdS complex indicate that the tunnel space, limiting the crystal growth, is the most probable site of nanoparticle formation. Properties of the nanoparticles can be modified by changing temperature, pH, etc. It is concluded that RPE can be used as a reagent for detoxification of cadmium ions and a matrix for synthesis of elongated CdS nanoparticles.

Cadmium↗
PubMed2005

[Structural properties of mixed saliva in persons with different levels of tooth resistance to caries].

Structural properties of mixed saliva were studied in 30 persons 16-18 years of age divided into 3 groups (10 persons in each) according to different levels of tooth resistance to caries -- 1st with high level of resistance (DMFT=0), 2nd with medium level of resistance (DMFT=4.3+/-0.82), 3rd with low level of resistance (DMFT=6.6+/-0.92). The difference between DMFT figures in groups 2 and 3 was insignificant. In salivary filtrate (collected in the rest conditions and after 5 g sugar load) pH (by potentiometry) and optical density (by photoelectric colorimetry) were determined. 60 saliva samples were collected and 240 determinations were made. In was found that 5 g sugar intake led to structural changes of oral fluid in all groups with different levels of tooth resistance to caries. But in persons with 0 caries incidence the oral fluid micelle resistance and saliva mineralizing capacity were higher than in persons with medium and low resistance to caries. The received data may be used for revelation of oral mineral homeostasis mechanisms and forecasting pathology arising in cases of its disturbance and for planning preventive and curative measures with consideration of their corrections depending upon the level of the individual resistance to caries.

Adolescent↗
PubMedDate not supplied

[Membrane-selective electrodes for drug analysis. Note II].

Seven membrane-selective electrodes with PVC matrix and liquid-membrane for N-butylscopolamine with different electroactive materials are presented. These electrodes have a linear response in the concentration range of 10(-6) - 10(-2) M N-butylscopolamine bromide, with a detection limit between 4.58 x 10(-7)M and 1.09 x 10(-6)M. These electrodes were used with good results for quantitative assay by direct potentiometry and potentiometric titration of N-butylscopolamine bromide from pharmaceutical formulations. Recovery was between 95.50% and 99.20% for N-butylscopolamine bromide of injectable solutions.

Algorithms↗
PubMedDate not supplied

Polyvinyl chloride matrix membrane electrodes for manual and flow injection analysis of chloroquine in pharmaceutical preparations.

Two types of polyvinyl chloride (PVC) matrix membrane electrodes responsive to the antimalarial drug chloroquine have been constructed, electrochemically evaluated, compared and used in pharmaceutical analysis. Type 1 is the classic PVC model with chloroquine-tetraphenylborate (TPB) sensor; Type 2 is a coated silver disk without internal filling solution. Both electrode types exhibited rapid linear potentiometric response to the logarithmic concentration of diprotonated chloroquine cation in the 10(-1) - 10(-6)M range with calibration slopes 28-30 mV/concentration decade over the pH range 1.8-6.2. These electrodes were sensitive enough to permit determination of chloroquine phosphate at concentrations as low as 5 microgram/mL with good accuracy and precision. Determination of chloroquine in various pharmaceutical preparations using direct potentiometry and potentiometric titration with NaTPB gave an average recovery of 98.8% of the nominal values (SD 0.5%). The Type 2 electrode was also assessed in a flow-through sandwich cell for flow injection analysis. Results were compared with data obtained by the U.S. Pharmacopeia method.

Chloroquine↗
PubMed1991

[Berberine-electrochemical detector for the determination of berberine-type alkaloids in various Chinese patent medicines by flow injection analysis].

A description is given for the preparation of flow through sensor and of the incorporation of the sensor into a flow injection analysis system. The parameters affecting the measurement are discussed. An accurate, convenient and rapid method is proposed for the determination of berberine-type alkaloids in various Chinese patent medicines (Coptis chinensis Franch., Phellodendron chinesis Schneid., xianglian wan, zuojin wan, ermiao wan and sanmiao wan). The slope is 54-60 mV/decade over the concentration range of 10(-3)-3 x 10(-6) mol/L berberine at pH 2-9.5. Direct potentiometry determination of berberine in various samples showed an average recovery of 99.5-103.5% and a relative standard deviation of 1.3-3.5% at a sampling rate of 120/h.

Berberine↗