A simple method for the accurate determination of free [Ca] in Ca-EGTA solutions

1982 ◽  
Vol 242 (5) ◽  
pp. C404-C408 ◽  
Author(s):  
D. M. Bers
Keyword(s):  
Association Constant ◽  
Accurate Determination ◽  
Tetraacetic Acid ◽  
Binding Parameters ◽  
Simple Method ◽  
Metal Ligands ◽  
Accurate Knowledge ◽  
Complex Solutions ◽  
Ethanesulfonic Acid

A simple method for the accurate determination of free [Ca] in ethyleneglycol-bis(beta-aminoethylether)-N,N'-tetraacetic acid (EGTA)-buffered Ca solutions is described. This method is useful for calibration of Ca macro- and microelectrodes to low free [Ca] and should improve the reliability of calculated free [Ca] in more complex solutions. Briefly, free [Ca] in Ca-EGTA solutions is measured with a Ca electrode, bound Ca is calculated, and Scatchard and double-reciprocal plots are resolved for the total [EGTA] and the apparent Ca-EGTA association constant (K'Ca) in the solutions used. The free [Ca] is then recalculated using the determined parameters, giving a more accurate knowledge of the free [Ca] in these solutions and providing an accurate calibration curve for the Ca electrode. These solutions can then be used to calibrate other Ca electrodes (e.g., Ca microelectrodes) or the calibrated Ca electrode can be used to measure free [Ca] in solutions containing multiple metal ligands. This method allows determination of free [Ca], K'Ca, and total [EGTA] in the actual solutions used regardless of pH, temperature, or ionic strength. It does not require accurate knowledge of K'Ca or EGTA purity and circumvents many potential errors due to assumption of binding parameters. K'Ca was found to be 2.45 +/- 0.04 X 10(6) M-1 in 100 mM KCl, 10 mM N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid, and 1 mM EGTA at pH 7.00 and 23 degrees C. Total [EGTA] varied with supplier but was always less than quoted.

scholarly journals Internal ice-sheet radar layer profiles and their relation to reflection mechanisms between Dome C and the Transantarctic Mountains

2001 ◽  
Vol 47 (157) ◽  
pp. 205-212 ◽  
Author(s):  
Martin J. Siegert ◽  
Shuji Fujita
Keyword(s):  
Accurate Determination ◽  
Ice Sheet ◽  
Radar Data ◽  
Internal Reflection ◽  
Frequency Data ◽  
Dual Frequency ◽  
Simple Method ◽  
Antarctic Research ◽  
Transantarctic Mountains

AbstractCauses of ice-sheet layering at ice depths greater than about 900 mina transect between Dome C and the Transantarctic Mountains are examined using 60 MHz radar data, collected in the 1970s by the U.K.–U.S.–Danish collaboration. Normally, a dual-frequency technique is required for accurate determination of internal reflection mechanisms. However, by extracting the depth-related features of 60 MHz radar profiles and comparing them with the dual-frequency data collected by the Japanese Antarctic Research Expedition, we have identified a simple method to estimate internal reflection mechanisms. Two zones can be distinguished: (1) the CA zone, where change in electrical conductivity due to variation in acidity is the major cause of internal reflection, and (2) the PCOF zone, where change in dielectric permittivity due to crystal-orientation fabrics is the major cause of internal reflections. Our analysis shows that the radar data reveal the development of PCOF zones in regions where large amounts of ice shearing are expected. This analysis shows how a similar interpretation of the full radar-data archive may reveal information on internal reflection mechanisms across a large part of the East Antarctic ice sheet.

A Method For Marking Small Juvenile Gastropods

1993 ◽  
Vol 73 (4) ◽  
pp. 963-966 ◽  
Author(s):  
Louis A. Gosselin
Keyword(s):  
Foraging Behaviour ◽  
Accurate Determination ◽  
Ecological Studies ◽  
Simple Method ◽  
Marine Gastropods ◽  
Small Juvenile ◽  
External Shell ◽  
Large Numbers ◽  
Invertebrate Larvae

Methods used to identify individual organisms consistently over time have been invaluable tools in ecological studies, enabling reliable assessments of time-dependent parameters such as growth and mortality, and an accurate determination of their variance. These methods have proved to be particularly amenable to gastropods owing to the presence of an external shell on which marks or tags can be applied with little or no adverse effects on the animal. Marking and tagging techniques have enabled the study of several ecological parameters in adult marine gastropods, including growth (Frank, 1965; Hughes, 1972; Palmer, 1983; Gosselin & Bourget, 1989), mortality (Frank, 1965; Hughes, 1972), movements (Frank, 1965; Chapman, 1986), and foraging behaviour (Menge, 1974; Hugheset al., 1992). Small organisms, however, can pose considerable problems for individual marking (Southwood, 1978). As a result, marking and tagging methods have seldom been applied to newly hatched or recently settled juvenile marine gastropods. Several methods have been developed for simultaneously labelling large numbers of invertebrate larvae (Levin, 1990), and some of these methods may be applicable to juvenile gastropods. The usefulness of these methods, however, is limited because all animals receive the same label and, consequently, individual animals cannot be recognized. To my knowledge, no method of individually marking very small juvenile marine gastropods has been documented. In fact, it is sometimes perceived that small juveniles cannot be individually marked due to their small size and sensitivity (Frank, 1965; Palmer, 1990). The object of this paper is to present a simple method of marking early juvenile gastropods, which consists of applying colour codes to the shells of individuals as small as 0·9 mm in length.

Preparation of U(VI) and Th(IV) alpha-sources from sea and fresh water samples by combining coprecipitation, solvent extraction and electrodeposition procedures

2004 ◽  
Vol 92 (3) ◽  
Author(s):  
R. Zarki ◽  
A. Elyahyaoui ◽  
A. Chiadli
Keyword(s):  
Solvent Extraction ◽  
Fresh Water ◽  
Water Samples ◽  
Sea Water ◽  
Accurate Determination ◽  
Simple Method ◽  
Considerable Saving ◽  
Initial Aqueous Solution ◽  
Initial Ph

SummaryA simple method combining coprecipitation, solvent extraction and electrodeposition for determining uranium and thorium in sea water and fresh water samples is developed. It offers a considerable saving in time, minimising chemical treatment and costs. The analytical procedure consists of enrichment of U and Th by coprecipitation with iron(III) hydroxides and subsequent extraction by diethylether solution and electrodeposition of each actinide in the extracting organic phase in which it was separated.The dependence of the coprecipitation, the extraction-electrodeposition and the overall yields of the above mentioned elements is examined in relation to the initial aqueous solution acidity and various amounts of iron carrier. At an initial pH between 6 and 10, quantitative coprecipitation of U and Th requires use of an Fe(III) quantity which depends on the acidity of these solutions. This quantity varies, under explored conditions, between 10 and 110mg/L. At a starting pH of 11, this coprecipitation becomes almost independent of Fe(III) amounts.The proposed procedure was used to analyse the content of U and Th isotopes in water samples. Recoveries of 60%-93% are obtained for uranium and 63%-86% for thorium. Good resolutions (37-56.5keV) are also achieved under optimum conditions. These resolutions allow to make accurate determination of U and Th isotopes in various water samples.

Simple method for the accurate determination of the refractive index of liquids in the infrared

1990 ◽  
Author(s):  
Philippe Marteau ◽  
G. Montixi ◽  
Jacques Obriot ◽  
T. K. Bose ◽  
J. M. St. Arnaud
Keyword(s):  
Refractive Index ◽  
Accurate Determination ◽  
Simple Method

scholarly journals A novel approach for detecting HMDSO poisoning of metal oxide gas sensors and improving their stability by temperature cycled operation

2015 ◽  
Vol 4 (2) ◽  
pp. 305-311 ◽  
Author(s):  
M. Schüler ◽  
T. Sauerwald ◽  
A. Schütze
Keyword(s):  
Accurate Determination ◽  
Sensor Data ◽  
Temperature Cycle ◽  
Simple Method ◽  
Self Monitoring ◽  
Linear Discriminant ◽  
Novel Approach ◽  
Metal Oxide Gas Sensors ◽  
The Stability

Abstract. In this paper we study the effect of hexamethyldisiloxane (HMDSO) vapor on an SnO2-based gas sensor (GGS 1330, UST Umweltsensortechnik GmbH, Geschwenda, Germany) in a temperature cycled operation (TCO). We show that HMDSO poisoning can be quantified at early stages (85 to 340 ppm × min) with a resolution of ±85 ppm × min using TCO. This novel approach for sensor self-monitoring provides a simple method for early detection of HMDSO poisoning. It is thereby possible to detect poisoning before the sensor function is strongly impaired. In this paper we show that by using an appropriate normalization of the sensor data, the stability of gas discrimination by linear discriminant analysis (LDA) can be improved, which in turn facilitates a more accurate determination of the poisoning state by a hierarchical LDA discrimination. For a specific temperature cycle and feature extraction approach, we show that identification of ethanol and carbon monoxide is still possible after poisoning with 900 ppm × min HMDSO, i.e. a HMDSO poisoning dose more than twice as high as required by DIN EN 50194-1.

Determination of the structure of liquids: an asymptotic approach

2013 ◽  
Vol 46 (6) ◽  
pp. 1582-1591 ◽  
Author(s):  
Martin Mayo ◽  
Eyal Yahel ◽  
Yaron Greenberg ◽  
El'ad N. Caspi ◽  
Brigitte Beuneu ◽  
...  
Keyword(s):  
Radial Distribution ◽  
Structure Factor ◽  
Accurate Determination ◽  
Interatomic Interaction ◽  
Liquid Structure ◽  
Distribution Functions ◽  
Asymptotic Dependence ◽  
Present Contribution ◽  
Simple Method

Accurate determination of a liquid structure, especially at high temperatures, remains challenging, as reflected in the scatter between different measurements. The experimental challenge is compounded by the process of the numerical transformation from the structure factor to the radial distribution function. The resulting uncertainty is often greater than that required to resolve issues associated with changes in the short-range order of the liquid, such as the existence of liquid–liquid phase transitions or correlations between thermophysical properties and structure. In the present contribution it is demonstrated for liquid bismuth as a model system that the structure factor can be obtained to high accuracy, by comparing several independent measurements in different setups. A simple method is proposed for improving the accuracy of the radial distribution functions, based on the extension of the finite range of momentum transfer,q, in the measured data by analytical asymptotic expressions. A unified mathematical formalism for the asymptotic dependence of the structure factor is developed and the asymptotic form of the Percus–Yevick hard-sphere solution is obtained as a special limiting case. The multiple expressions in the literature are shown to reflect uncertainty in the nature of the repulsive interatomic interaction at short separation distances. Applying this asymptotic method, it is shown that it enables access to details of the fine structure of the liquid and its temperature dependence.

scholarly journals HILIC -MS/MS Analysis of Adenosine in Patient Blood

Separations ◽  
2021 ◽  
Vol 8 (11) ◽  
pp. 222
Author(s):  
Christina Virgiliou ◽  
Nikolaos Fragakis ◽  
Melani Sotiriadou ◽  
Vassilios Vassilikos ◽  
Spiros Gerou ◽  
...  
Keyword(s):  
Accurate Determination ◽  
Solvent Mixture ◽  
Clinical Samples ◽  
Hydrophilic Interaction ◽  
Spectrometry Method ◽  
Simple Method ◽  
Physiological Processes ◽  
Pre Treatment ◽  
Successful Prevention

Adenosine is a purine ribonucleoside with important roles in various physiological processes. A number of studies have indicated the importance of adenosine in cardiovascular diseases including syncope; however, the accurate determination of adenosine in human blood is challenging due to the molecule’s instability. In the present study, we report a simple method for the pre-treatment of blood samples and the development of a fast and efficient hydrophilic interaction chromatographic tandem mass spectrometry method for the analysis of adenosine in patient blood. During collection, samples were mixed directly with a solvent mixture containing 95% acetonitrile and 10 mM ammonium formate in a Vacutainer tube, resulting in successful prevention of adenosine metabolic processes and direct blood sample deproteinization. The method was validated according to bioanalytical industry guidelines and found to be accurate, repeatable, specific and sensitive with LLOQ 0.005 μg/mL, thus allowing its application in the analysis of real clinical samples.

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