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At least 19 recordsLinked to original sources
PubMed1977

[Conductometry in determining measurements of urine electrolyte concentration (author's transl)].

1. Na+ concentration, measured by the flame photometer, cryoscopic osmolality, and the specific electrolyte conductivity of urine show a close statistical correlation if only small amounts of a molecular disperse solution are dissolved in the urine. 2. Since conductance of a fluid is an expression of its ion concentration, better relationships exist between Na+ concentration and conductivity than between Na+ concentration and osmolality. 3. In the presence of large amounts of glucose in the urine, osmolality no longer represents the electrolyte content, and therefore no longer serves as a parameter of renal concentration power. On the other hand, the close correlation between conductance and Na+ concentration remains. 4. Conductometry supplements osmometry significantly by its selective capacity to determine electrolyte components in the urine. 5. Owing to the short time spent on the method and small errors in technique, it remains debatable whether conductometry is preferable to osmometry in normal cases for determining measurements in concentration in the urine.

Child↗
PubMed2002

The determination of levofloxacin by flow injection analysis using UV detection, potentiometry, and conductometry in pharmaceutical preparations.

A flow injection analysis (FIA) using UV detection, potentiometry and conductometry for levofloxacin (LVF) are described in this study. The best solvent system was found to consist of 0.2 M acetate buffer at pH 3 having 10% MeOH. A flow rate of 1 ml min(-1) was pumped and active material was detected at 288 nm. The detection limit (LOD) and limit of quantification (LOQ) for FIA were calculated to be 3 x 10(-7) M (S/N = 3) and 1 x 10(-7) M (S/N = 10), respectively. In the analysis of tablets, the RSD values were found to be 0.83, 0.98 and 0.99 for FIA, potentiometric and conductometric methods, respectively.

Conductometry↗
PubMedDate not supplied

[Use of methods of derivative conductometry and photometry for assessing the structure of a cellular suspension].

Experimental proofs for the possibility of studying the dynamical structure of rotatory moving erythrocyte suspension with the methods of derivative conductometry and photometry are presented. The amplitude of the recorded impulses was proportional to the cell concentration and the angle velocity, and strongly depended on the shape of the suspended cells.

Cell Movement↗
PubMed2006

NMR diffusometry and conductometry study of the host-guest association between beta-cyclodextrin and dodecane 1,12-bis(trimethylammonium bromide).

Surfactants form association complexes with cyclodextrins. In the present investigation we have used NMR-diffusometry and electrical conductivity to follow the interactions which take place between beta-cyclodextrin and a bolaform surfactant: dodecane 1,12-bis(trimethylammonium bromide). Both (1)H NMR self-diffusion and conductometry data indicate the formation of a 1:1 inclusion complex. Assuming this stoichiometry, it was possible to calculate the association constant; from the analysis of the self-diffusion coefficients of free beta-cyclodextrin and the bolaform surfactant an association constant K=3x10(3)M(-1) was obtained while the analysis of conductivity data gave a comparable value of K=2.5x10(3)M(-1).

Journal Article↗
PubMedDate not supplied

The kinetics of hydroxyl-radical-induced strand breakage of hyaluronic acid. A pulse radiolysis study using conductometry and laser-light-scattering.

Hydroxyl radicals were generated radiolytically in N2O- and N2O/O2(4:1)-saturated aqueous solutions of hyaluronic acid. The hydroxyl radicals react rapidly with hyaluronic acid mainly by abstracting carbon-bound H atoms. As a consequence of subsequent free-radical reactions, chain breakage occurs the kinetics of which has been followed using the pulse radiolysis technique. In the absence of oxygen, strand breakage was followed by the change in conductivity induced by the release of cationic counterions condensed at the surface of hyaluronic acid which is a polyanion consisting of subunits of glucuronic acid alternating with N-acetyl-glucosamine. It appears that strand breakage is not due to one single first-order process, however, the contributions of the different components cannot be adequately resolved. At pH 7 the overall half-life is 1.4 ms, in both acid and basic solutions the rate of free-radical induced strand breakage is accelerated (at pH 4.8, t1/2 = 0.6 ms; at pH 10, t1/2 = 0.18 ms). In the absence of oxygen there is no effect of dose rate on the kinetics of strand breakage. In the presence of oxygen in addition to conductometric detection, strand breakage was also followed by changes in low-angle laser light-scattering. These two techniques are complementary in that in this system the conductometry requires high doses per pulse while the light-scattering technique is best operated in the low-dose range. In the presence of oxygen a pronounced dose-rate effect is observed, e.g. at pH 9.7 after a dose of 9.4 Gy the overall half-time is approx. 0.5 s, while after a dose of 6.6 Gy the half-time is approx. 0.23 s. Both the yield and the rate of strand breakage increase with increasing pH, e.g. at pH 7 G(strand breaks) = 0.7 x 10(-7) mol J-1 and at pH 10.4, 4.8 x 10(-7) mol J-7. The radiolytic yields of CO2, H2O2, organic hydroperoxides, O2.- and oxygen consumption have been determined in gamma-irradiated N2O/O2(4:1)-saturated solutions of both hyaluronic acid and beta-cyclodextrin.

Carbohydrate Sequence↗
PubMed1990

[Automatic blood group determination in the ABO- and Rh-system using conductometry].

A method was developed and tested on the basis of conductometry for determining blood group-specific agglutinates in the AB0 and Rh-system (D). By comparing the measured particle numbers before and after administration of specific antisera or test erythrocytes and objective evaluation can be made whether agglutination has occurred or not. The calculated degrees of agglutination were compared depending on the method, sex, and age of patients. The method can be automated.

ABO Blood-Group System↗
PubMed1989

[Diagnosis of mucoviscidosis by examination of sweat: value of conductometry].

Two methods for the determination of sodium in the sweat after stimulation by pilocarpine-iontophoresis were compared in 227 patients, among them 27 with a known cystic fibrosis. These two methods were 1. the standardized method by flame fotometry (State Pharmacopoeia of the German Democratic Republic) and 2. the determination of the sweat conductance by the new apparatus "CF-Conductognost". Both methods showed a good correlation. We recommend the conductometry for the decentralized screening because it saves time and gives results immediately. But in all patients with a questionable or pathologic value of conductance the sweat test should be repeated with the standardized method. This concerns only about 10 per cent of all patients.

Adolescent↗
PubMed2005

Determination of the molecular complexation constant between alprostadil and alpha-cyclodextrin by conductometry: implications for a freeze-dried formulation.

The binding constant between alprostadil (PGE1) and alpha-cyclodextrin (alpha-CD) was determined at four temperatures using conductance measurements. Alpha-cyclodextrin is an excipient material in Caverject dual chamber syringe (DCS) that was added to enhance stability. The binding constant was used to calculate the amount of PGE1 free upon reconstitution and injection, since only the free drug is clinically active. The conductivity measurement is based on a decrease in specific conductance as alprostadil is titrated with alpha-CD. The change in conductivity was plotted versus free ligand concentration (alpha-CD) to generate a binding curve. As the value of the binding constant proved to be dependent on substrate concentration, it is really a pseudo binding constant. A value of 742+/-60 M(-1) was obtained for a 0.5 mM solution of alprostadil at 27 degrees C and a value of 550+/-52 M(-1) at 37 degrees C. These results compare favorably to values previously obtained by NMR and capillary electrophoresis. Calculation of the fraction PGE1 free upon reconstitution and injection show it to approach the desired outcome of one. Hence, the amount of drug delivered by Caverject DCS is nominally equivalent to that delivered by Caverject S. Po., a predecessor product that contains no alpha-cyclodextrin.

Algorithms↗
PubMed1963

Studies on rapidly frozen suspensions of yeast cells by differential thermal analysis and conductometry.

Few, if any, yeast cells survived rapid cooling to -196 degrees C and subsequent slow warming. After rapid freezing, the suspensions absorbed latent heat of fusion between -15 degrees and 0 degrees C during warming, and the relation between the amount of heat absorbed and the concentration of cells was the same as that in equivalent KCl solutions, indicating that frozen suspensions behave thermally like frozen solutions. The amount of heat absorbed was such that more than 80 per cent of the intracellular solution had to be frozen. The conductometric behavior of frozen suspensions showed that cell solutes were still inside the cells and surrounded by an intact cell membrane at the time heat was being absorbed. Two models are consistent with these findings. The first assumes that intracellular freezing has taken place; the second that all freezable water has left the cells and frozen externally. The latter model is ruled out because rapidly cooled cells do not shrink by an amount equal to the volume of water that would have to be withdrawn to prevent internal freezing.

Cell Count↗
PubMedDate not supplied

[Low-frequency conductometry of the tissues and organs of undefined geometrical form].

The authors review potentialities of the use of the four-probe methods for measuring specific electric conductivity (SE) on biological objects. An analysis was made of the main causes of the method limitations and occurrence of errors during low-frequency measurements. As a result a design of a four-electrode conductometric set up is suggested with a purpose of measuring SE of biological objects of undefined geometrical form with a high accuracy of measurements at low frequencies. The positive effect was attained at the expense of reducing the impedance of potential electrodes at low frequencies.

Cell Membrane↗