1,721,503 research outputs found
Approximation Properties of the Edgeworth Cramer Series and Determination of Peak Parameters of Chromatographic Peaks
No full textThe approximation properties of the Edgeworth-Cramér series with respect to the Martln-Synge and the stochastic model of the chromatographic peak were analyzed. It has been shown that these series have asymptotic properties, the asymptotic quantity being respectively the number of theoretical plates (or the column length) and the mean number of adsorption- desorption steps. Thus the fundamental role of these series In chromatographic theory is established. Two distances between the original peak and the approximated peak, such as the classical Lévy distance and the integral of the squared deviations were considered. The minimum properties of these distances with respect to the peak parameters were analyzed. Examples of unbiased peak parameter recovery by nonlinear least-squares curve fitting are reported. Peak parameter recovery precision and accuracy are discussed In reference to the series expansion order and to the peak skewness. © 1982, American Chemical Society. All rights reserve..
ENVIREN
No full textIl Laboratorio ENVIREN si occupa di tecnologie per il monitoraggio ambientale nei comparti aria, acqua, suolo e rifiuti; sviluppa metodi, modelli e strumenti per la gestione della risorsa idrica, per il controllo della qualità dell'aria, e per la pianificazione del territorio; si occupa inoltre di tecnologie e tecniche per la prevenzione, riduzione e trattamento dei rifiuti e per la valorizzazione energetica e in materia di rifiuti e residui di processo.
ENVIREN nasce dall'aggregazione delle competenze scientifiche, tecnologiche e strumentali presenti nei laboratori LaRIA, LARA e LITCAR; esso si avvale di uno Steering Committee che coordina i tre filoni di attività e di uno Staff di Coordinamento per le attività di management
Microsymposium on chemometric methods in analytical chemistry, Ferrara, Italy, 9–10 April 1987
No full textPropagation of Infinitesimal Perturbations In Gas-solid Chromatographic Columns At Finite Dilution - Mobile Monomolecular and Multimolecular Adsorption
No full textSeparazioni HPLC preparative su fase chirale. Un'alternativa importante per la separazione di enantiomeri
No full textThe characteristic function method in the stochastic theory of cromatography
No full textThe stochastic theory of chromatography is reconsidered through the fundamental characteristic function method of the
probability theory. The means of obtaining expressions for plate height H, specific asymmetry Z, and specific flatness F
is described, and six different chromatographic models of progressively greater complexity are analyzed. All the models
assume a constant mobile-phase velocity and equal sorption sites and do not take into account flow pattern and mobile-phase
diffusion effects. The role of the random nature of both the stationary-phase entries and the sorption processes is considered
from a general point of view. The rate of convergence toward the Gaussian law is described by using the general Berry-Essden
theorem of the probability theory, and the approximation properties of the Edgeworth-Cramer series are described for a
general chromatographic model. Examples of mixed retention on a single site by a bifunctional solute molecule are given,
and influence on the peak shape is described
Barley starch granules subject to SPLITT cell fractionation and Sd/StFFF size characterization
No full textThe coupling of two separation techniques is proposed as a methodology able to fractionate, starch granules of different botanical origins, both on preparative and analytical scale. The split flow thin cell (SPLITT cell) was optimized to produce a binary separation of the starch granules into two different size classes with a 5 mum cutoff point. The size separation was always better than 80%. The Sedimentation Steric Field Flow Fractionation (Sd/StFFF) provides sample particle size distribution (PSD) and is used here to control the SPLITT fractions. The proposed techniques, especially the former, are gentle and easy to use. Both the SPLITT and Sedimentation Fractionation results were checked by scanning electron microscopy (SEM). The procedure was originally applied to two samples from barley. The bimodal diameters were computed
Applications of 18F-Fluorodesoxyglucose PET Imaging in Leukemia
No full text: The main finding that 18F-FDG PET imaging can reveal in patients with leukemias is the presence of bone marrow (BM) infiltration in both acute or chronic forms. This ability can influence and guide the use of BM biopsy but also assess to therapy response. Additionally 18F-FDG PET imaging has been reported as particularly useful for the diagnosis of leukemias in patients with non specific symptoms. In the case of acute leukemias it revealed also a role for the evaluation of extramedullary forms while in the case of chronic forms a role for the assessment of Richter transformation has been reported
Cromatografia HPLC non-lineare
No full textAl fine di ottenere valori di risoluzione elevati, i cromatografisti analitici scelgono condizioni sperimentali in cui gli effetti dovuti alla non linearità siano il più possibile minimizzati. Una conoscenza accurata di questi stessi fenomeni può portare tuttavia all'ottenimento di condizioni utili per la separazione. La chiave per la comprensione della non linearità e di come essa intervenga nella separazione è rappresentata dalle isoterme di adsorbimento in molte condizioni e specialmente nel caso delle separazioni chirali; la determinazione delle isoterme di adsorbimento rappresenta uno strumento indispensabile per l'interpretazione el'ottimizzazione della separazione
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