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Results for “Conductometry”

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PubMed1980

Conductimetric determination of methimazole.

Methimazole, a thyroid inhibitor, is a weak acid. In this communication, its authentic powder and its tablets (Tapazole) are assayed via its acidic property in aqueous medium. The equivalence point is determined conductimetrically. The average percent recovery for its authentic powder and tablets were found to be 99.30 +/- 1.30 and 98.27 +/- 1.81 respectively. The method, proposed in this study, is simple, rapid and can be adopted for routine analysis in quality control laboratories.

Chemical Phenomena↗
PubMed1980

[Comparison of the reliability of 2 different methods of carboxyhemoglobin determination].

This paper was aimed at an evaluation of two different methods of carboxyhemoglobin determination in blood: colorimetric method according to Wolff and conductometric method. In result of this comparison it has been established that Wolff's method was less accurate and gave higher results than did the conductometric method. Reliability of both methods was evaluated and the reasons for Wolff's method errors were discussed.

Calibration↗
PubMed1994

Assessment of refill and hypovolaemia by continuous surveillance of blood volume and extracellular fluid volume.

During renal replacement therapy hypovolaemia due to ultrafiltration (UF) may, when not sufficiently counteracted by refill from the interstitium, result in hypotension. Combining two recently developed methods the haemodynamic process of refill was studied in order to find characteristics featuring hypotension. Relative blood volume (BV) and extracellular fluid volume (EFV) were measured continuously in 40 stable haemodialysis patients by means of an optical and a conductivity technique respectively. Regarding their postdialytic (PD) EFV the patients were divided into three groups: normohydrated (N, n = 20), dehydrated (D, n = 11) and overhydrated (O, n = 9). Significant differences between the groups were assessed in BV decrease (after 2 h until the end of treatment P < 0.05 and after 3 h P < 0.01), EFV decrease (after 3 h P < 0.05) and occurrence of hypotensive episodes (N,5; D,7; O,none; P < 0.01). During the entire session the speed of BV decrease was significantly higher in hypotensive patients (H) than in non-hypotensive patients (non-H). At the moment of hypotension (after 141 +/- 49 min) residual BV was less (P < 0.0005) in H (87.7 +/- 5.2%) than at the corresponding moment in non-H patients (96.5 +/- 4.0%). PD BV and PD EFV, both expressed as a percentage of the starting value, correlated significantly (r = 0.63, p < 0.005) and UF-volume (differences between the groups were not significant) correlated to EFV decrease (r = 0.45, P < 0.005). In conclusion, the combination of both non-invasive methods elucidates the pathophysiology of UF-induced hypotension and provides a means of reducing dialysis morbidity. The influence of tissue hydration state on these variables has been shown.

Aged↗
PubMedDate not supplied

[A conductometric method of measuring enzymatic catalysis].

Theoretical bases of the conductometric method of measurements are considered, respective formulas and equations are presented. The possibilities of application of this method for registration of the enzyme processes are shown, as well as examples of its use in conductometric classic procedure and in conductometric enzyme biosensors. Different methods of immobilization of the biological material on the surface of the transducers, schemes and methods of measurements are presented, the advantages and disadvantages of this method as compared with general biochemical methods are discussed.

Biosensing Techniques↗
PubMed1994

Elastolytic activity of MAP1, a protease from Myxococcus xanthus.

MAP1, a protease isolated from Myxococcus xanthus, is demonstrated to be an elastase. Although its elastolytic activity is lower than that of other well-known elastases, the size distribution of solubilized elastin peptides is similar. MAP1 as pancreatic elastase releases peptides with molecular weights higher than 10,000. However, the specificity of MAP1 is different since this enzyme cannot hydrolyze alanine oligomers as do pancreatic and Pseudomonas aeruginosa elastases.

Animals↗
PubMedDate not supplied

Conductometric biosensor for ethanol detection based on whole yeast cells.

The quantification of ethanol in alcoholic beverages was performed by yeast cell-based conductometric biosensor. A membrane with yeast cells immobilized in 2% Ca-alginate gel was attached on gold planar electrodes. Changes in conductivity due to the specific consumption of ethanol by yeast cells were registered by the computer-controlled sensor system. The response time of the constructed microbial sensor was less than 5 min, linearity (in a logarithmic scale) was observed in the range of 5-100 mM alcohol concentration. It was established that pH value in their region from 5 to 8 did not influence the levels of initial signal. The increase of a buffer capacity in the sample results in the decrease of the biosensor output. The minimal detectable level of ethanol was 1 mM and the relative standard deviation appeared to be 10-12% for 15 repeated assays. When the system was operated and stored at 20-25 degrees C, the biosensor response was stable for only 3 days. However, when the microbial sensor was stored at 4 degrees C, the system was stable up to 12 days. Good correlation between the results obtained by a conductometric cell-biosensor and gas chromatograph was observed.

Alcoholic Beverages↗
PubMedDate not supplied

[Use of conductometric microsensors for studying kinetic parameters of enzymes].

An alternative method based on thin-film conductometric microsensor is suggested for studying enzyme kinetics. It is established that the immobilized enzyme as well as soluble one is described by the classic lows of enzyme kinetics. Major parameters (Km and Vmax) are identical to those measured by the widely used methods and their amounts are 1.33 mM and 9.04 microS/min for soluble urease and 3.73 mM and 13.8 microS/min for immobilized urease; 5.26 mM and 13.9 microS/min for immobilized glucose oxidase; 13.6 mM and 122.0 microS/min for immobilized acetyl cholinesterase; 10.8 mM and 129.9 microS/min for immobilized butyryl cholinesterase. The possibility of conductometric analyzer application for detection of toxin concentration, in particular pesticides, is shown. Advantages and disadvantages of the system suggested are discussed.

Biosensing Techniques↗
PubMed1995

Measurement of tear electrolyte concentration and turnover rate using a flexible conductimetric sensor.

Tear fluid conductivity was measured by a non-invasive method. A flexible 3 mm-wide conductimetric sensor was placed inside the human subjects temporal lower cul-de-sac (similar to Schirmer test strip), and used to evaluate electrolyte concentration and turnover rate in tear for normal, healthy subjects aged between 30 to 85 years in a normal, light indoor environment. The tear electrolyte concentration was calculated from tear conductivity to give a mean value of 297 mEq/l (S.D. 30 mEq/l; n = 29) which was consistently with previously reported values. Tear turnover rate was calculated by a single exponential equation of tear conductivity change, following the application to the eye-drops of 40.0 milligrams sodium chloride solution. The mean turnover rate was 44.2% per minute (S.D. = 13.3% per minute; n = 30), being in agreement with previously reported values.

Adult↗
PubMedDate not supplied

[A comparative evaluation of the differential count of peripheral blood leukocytes using the Cell-Dyn 3500 and NE-7000 hematology analyzers].

Two blood analyzers, Cell-Dyn 3500 (Abbott) and NE-7000 (Sysmex) are compared as regards their use in clinics of a general profile. Both devices can differentiate the leukocytic formula by 5 parameters (neutrophils, lymphocytes, monocytes, eosinophils, and basophils) and possess a system of alarm signals indicating changes in the leukocytic formula. A total of 165 peripheral blood samples stabilized with K3-EDTA were examined. Visual assessment of stained preparations, 200 cells per smear, was the reference method. Both devices yielded similar results of leukocyte counting, were in good correlation with the visual method in assessment of neutrophils, lymphocytes, and eosinophils. Both devices proved to be inaccurate in counting monocytes, which was due to a great variety of morphologic forms of these cells. In addition, the number of false-positive and false-negative results was assessed. No abnormalities were detected in the 20 samples which were assessed as "negative" by the analyzers. Study of the peripheral blood by automated blood analyzers Cell-Dyn 3500 and NE-7000 helps detect a pathological leukocytic formula in 100% cases, although the type of shifts is not always precisely assessed by these devices. Therefore, morphological control is needed in case of alarm signals.

Conductometry↗
PubMed1977

Evaluation of electrolytic conductivity detection for gas-liquid chromatographic screening of some organonitrogen herbicides and fungicides in foods.

Electrolytic conductivity detection for the gas-liquid chromatographic (GLC) screening of 15 organonitrogen herbicides and fungicides was investigated. Spiked samples of crop material was extracted with acetone and the filtered sample extracts were partitioned with methylene chloride-petroleum ether (1+1) followed by second and third extractions with methylene chloride. The combined organic extracts were evaporated to dryness and the residues were dissolved in hexane for cleanup on a 2% deactivated Florisil column. The pesticide fractions were determined directly by GLC. All pesticides could be detected at 0.1 ppm in the foods studied.

Chromatography, Gas↗
PubMed1996

[Determination of orthophosphoric and orthophosphorous acids in the workplace air using ion chromatography].

The authors elaborated a method measuring air level of orthophosphorous and orthophosphoric acids by means of ion chromatography within the range of 0.1-25 mg/cu m. The samples are extracted through concentration on a filter. The analysis regime includes depression of the background levels. The separating column (4 x 200 mm) is filled with anion exchanger BT IAN, the suppressing column (6 x 150 mm) is filled with cation exchanger Dowex 50 x 8, the elutriating agent is 1.5 mM of sodium carbonate, the detector is conductometric. Minimal amounts of ions that could be detected in the analyzed solution are 7-10 ng (HPO32-), 10-15 ng (HPO 42-). The method is designed to analyze the air of workplace.

Air Pollutants, Occupational↗
PubMedDate not supplied

[Development of enzyme biosensor based on trypsin and conductometric thin-film electrodes for protein and artificial substrates determination].

Two analytical systems based on the soluble and immobilized trypsin and conductometric thin-film electrodes were developed to measure concentration of artificial substrate and protein in solution. It was shown that these systems allow one to determine concentrations of Ha-benzoyl-L-arginin-ethyl-ester in the range of 0.1-1.0 mM and concentrations of HSA: 0.1-2.0 mg/ml with soluble and 0.1-0.8 mg/ml with immobilized trypsin.

Arginine↗