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Precise Results (precise + result)

Distribution by Scientific Domains
Chemistry75%

Selected Abstracts

Diffraction peak profiles from spherical crystallites with lognormal size distribution

JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 5 2003
T. Ida
An efficient and accurate method to evaluate the theoretical diffraction peak profiles from spherical crystallites with lognormal size distribution (SLN profile) is presented. Precise results can be obtained typically by an eight-term numerical integral for any values of the parameters, by applying an appropriate substitution of the variable to the integral formula. The calculated SLN profiles have been verified by comparison with those calculated by inverse Fourier transform from the exact analytical solution of the Fourier-transformed SLN profile. It has been found that the shape of the SLN profile strongly depends on the variance of size distribution. When the logarithmic standard deviation , of the size distribution is close to 0.76, the SLN profile becomes close to a Lorentzian profile, and `super-Lorentzian' profiles are predicted for larger values of ,, as has been concluded by Popa & Balzar [J. Appl. Cryst. (2002), 35, 338,346]. The intrinsic diffraction peak profiles of an SiC powder sample obtained by deconvolution of the instrumental function have certainly shown `super-Lorentzian' line profiles, and they are well reproduced by the SLN profile for the value , = 0.93. [source]

Rapid detection of yeast rRNA genes with primed in situ (PRINS) labeling

FEMS YEAST RESEARCH, Issue 4 2009
Maciej Wnuk
Abstract In yeast, rRNA genes can be detected with the FISH technique using rRNA gene probes. This technique yields reliable, reproducible and precise results, but is time-consuming. Here, the primed in situ DNA synthesis (PRINS) procedure has been optimized for rapid detection of yeast rRNA genes. PRINS, which is as sensitive as PCR and allows cytological localization of analyzed sequences, can be adapted for various screening tests requiring fast labeling of rRNA genes. [source]

Rapid chemiluminometric determination of gabapentin in pharmaceutical formulations exploiting pulsed-flow analysis

LUMINESCENCE: THE JOURNAL OF BIOLOGICAL AND CHEMICAL LUMINESCENCE, Issue 1 2009
Matías Manera
Abstract In this study, a straightforward and automated pulsed flow-based procedure was developed for the chemiluminometric determination of gabapentin [1-(aminomethyl)cyclo-hexaneacetic acid], a new generation antiepileptic drug, in different formulated dosage forms. The software-controlled time-based injection method capitalizes on the decrease of the background chemiluminescence (CL) readout of the luminol,hypochlorite reaction in the presence of gabapentin. In short, gabapentin works as a hypochlorite scavenger. The analytical procedure was implemented in a multi-pumping flow network furnished with a suite of microdispensing solenoid-actuated pumps. The diaphragm-type micropumps might be configured to operate as fluid propellers, commutation units and metering injectors. A dynamic linear working range for gabapentin concentrations in the range 60,350 µmol/L was obtained, with an estimated detection limit of 40 µmol/L. The flow analyser handles about 41 injections/h and yields precise results (RSD < 2%). The miniaturized flow analyser thus has potential to be exploited for in-line monitoring of drug manufacturing within the quality assurance framework of modern pharmaceutical companies. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Analysis of aromatic amines in cigarette smoke,

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 18 2003
Regina Stabbert
A method for the analysis of o -toluidine, o -anisidine, 2-naphthylamine, and 4-aminobiphenyl in cigarette mainstream smoke has been developed, which combines the sensitivity of their pentafluoropropionyl (PFP) derivatives in negative ion chemical ionization (NICI) mode with the selectivity of the gas chromatography/tandem mass spectrometry (GC/MS/MS) technique. The use of four deuterated analogues as internal standards along with the application of the standard addition method results in accurate and precise results; the interday precision for the aromatic amines was 3,10% and the accuracy ranged from 97,100%. This method was applied to two American-blend University of Kentucky reference cigarettes, eight American-blend market cigarettes, a bright (flue-cured) tobacco cigarette, and an electrically heated cigarette smoking system (EHCSS). For the American-blend cigarettes there was a linear correlation between aromatic amine yields and mainstream smoke ,tar' (,tar',=,total particulate matter , (nicotine,+,water)), whereas the bright tobacco cigarette and the EHCSS demonstrated significantly lower aromatic amine yields on an equal ,tar' basis. The results support the hypothesis that the nitrogen content of the tobacco, and above all the cigarette combustion temperature, are determining factors for the yields of aromatic amines in smoke. Copyright © 2003 John Wiley & Sons, Ltd. [source]