Development and validation of an HPLC method for the determination of spironolactone and its metabolites in paediatric plasma samples

Abstract An HPLC method has been developed and validated for the determination of spironolactone, 7a-thiomethylspirolactone and canrenone in paediatric plasma samples. The method utilises 200 µl of plasma and sample preparation involves protein precipitation followed by Solid Phase Extraction (SPE). Determination of standard curves of peak height ratio (PHR) against concentration was performed by weighted least squares linear regression using a weighting factor of 1/concentration2. The developed method was found to be linear over concentration ranges of 30–1000 ng/ml for spironolactone and 25–1000 ng/ml for 7a-thiomethylspirolactone and canrenone. The lower limit of quantification for spironolactone, 7a-thiomethylspirolactone and canrenone were calculated as 28, 20 and 25 ng/ml, respectively. The method was shown to be applicable to the determination of spironolactone, 7a-thiomethylspirolactone and canrenone in paediatric plasma samples and also plasma from healthy human volunteers.

Moderately elevated plasma homocysteine, MTHFR genotype and risk for stroke, vascular dementia and alzheimer's disease in northern ireland

BACKGROUND AND PURPOSE: Elevated plasma homocysteine level has been associated with increased risk for cardiovascular and cerebrovascular disease. Variation in the levels of this amino acid has been shown to be due to nutritional status and methylenetetrahydrofolate reductase (MTHFR) genotype. METHODS: Under a case-control design we compared fasting levels of homocysteine and MTHFR genotypes in groups of subjects consisting of stroke, vascular dementia (VaD), and Alzheimer disease patients and normal controls from Northern Ireland. RESULTS: A significant increase in plasma homocysteine was observed in all 3 disease groups compared with controls. This remained significant after allowance for confounding factors (age, sex, hypertension, cholesterol, smoking, creatinine, and nutritional measures). MTHFR genotype was not found to influence homocysteine levels, although the T allele was found to increase risk for VaD and perhaps dementia after stroke. CONCLUSIONS: We report that moderately high plasma levels of homocysteine are associated with stroke, VaD, and Alzheimer disease. This is not due to vascular risk factors, nutritional status, or MTHFR genotype

The development and validation of liquid chromatography method for the simultaneous determination of metformin and glipizide, gliclazide, glibenclamide or glimperide in plasma

This article describes the development of SPE and HPLC methods for the simultaneous determination of metformin and glipizide, gliclazide, glibenclamide or glimperide in plasma. Several extraction and HPLC methods have been described previously for the determination of each of these analytes in plasma separately. The simultaneous determination of these analytes is important for the routine monitoring of diabetic patients who take combination medications and for studying the pharmacokinetics of the combined dosage forms. In addition this developed method can serve as a standard method for the plasma determination of these analytes therefore saving time, effort and money. The recoveries of the developed methods were found to be between 76.3% and 101.9%. The limits of quantification were between 5 and 22.5 ng/ml. The intraday and interday precision (measured by coefficient of variation, CV%) was always less than 9%. The accuracy (measured by relative error %) was always less than 12%. Stability analysis showed that all analytes are stable for at least 3 months when stored at -70degreesC. (C) 2004 Elsevier B.V. All rights reserved.

Charge-state distribution and Doppler effect in an expanding photoionized plasma.

The charge state distributions of Fe, Na, and F are determined in a photoionized laboratory plasma using high resolution x-ray spectroscopy. Independent measurements of the density and radiation flux indicate unprecedented values for the ionization parameter ���¾=20 25 erg cm s-1 under near steady-state conditions. Line opacities are well fitted by a curve-of-growth analysis which includes the effects of velocity gradients in a one-dimensional expanding plasma. First comparisons of the measured charge state distributions with x-ray photoionization models show reasonable agreement.

Plasma-based studies with intense X-ray and particle beam sources

The construction of short pulse (

Direct observation of strong coupling in a dense plasma

We present differential x-ray scattering cross sections for a radiatively heated plasma showing overall consistency, in both form and absolute value, with theoretical simulations. In particular, the evolution of the plasma from a strongly coupled high density phase to a lower density weakly coupled phase is quite clearly shown in both experiment and simulation. The success of this experiment shows that x-ray scattering has the potential to become an extremely useful diagnostic technique for dense plasma physics.

Atomic oxygen surface loss coefficient measurements in a capacitive/inductive radio-frequency plasma

Spatially resolved measurements of the atomic oxygen densities close to a sample surface in a dual mode (capacitive/inductive) rf plasma are used to measure the atomic oxygen surface loss coefficient beta on stainless steel and aluminum substrates, silicon and silicon dioxide wafers, and on polypropylene samples. beta is found to be particularly sensitive to the gas pressure for both operating modes. It is concluded that this is due to the effect of changing atom and ion flux to the surface. (C) 2002 American Institute of Physics.

Fast heating of ultrahigh-density plasma as a step towards laser fusion ignition

ate studies(2) and fusion energy research(3,4). Laser-driven implosions of spherical polymer shells have, for example, achieved an increase in density of 1,000 times relative to the solid state(5). These densities are large enough to enable controlled fusion, but to achieve energy gain a small volume of compressed fuel (known as the 'spark') must be heated to temperatures of about 10(8) K (corresponding to thermal energies in excess of 10 keV). In the conventional approach to controlled fusion, the spark is both produced and heated by accurately timed shock waves(4), but this process requires both precise implosion symmetry and a very large drive energy. In principle, these requirements can be significantly relaxed by performing the compression and fast heating separately(6-10); however, this 'fast ignitor' approach(7) also suffers drawbacks, such as propagation losses and deflection of the ultra-intense laser pulse by the plasma surrounding the compressed fuel. Here we employ a new compression geometry that eliminates these problems; we combine production of compressed matter in a laser-driven implosion with picosecond-fast heating by a laser pulse timed to coincide with the peak compression. Our approach therefore permits efficient compression and heating to be carried out simultaneously, providing a route to efficient fusion energy production.