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.

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 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.

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.

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