177 research outputs found
Verbeteringen aan monster- en variabelenselectie bij multivariate kalibratie = Improvements in sample and variable selection in multivariate calibration
No full textContains fulltext :
135139.pdf (Publisher’s version ) (Open Access)Radboud Universiteit Nijmegen, 16 januari 2015Promotores : Buydens, L.M.C., Heyden, Y. Vander141 p
Chemometric strategies in analysis of chromatographic-mass spectrometry data
No full textThe coupling of chromatography and mass spectrometry (MS) provides a powerful tool for the chemical analysis of complex matrices [1-3]. The most common analytical techniques used in the separation step are gas chromatography (GC), liquid chromatography (LC), and capillary electrophoresis (CE) [4-12]. GC-MS allows the separation of volatile and semivolatile compounds, LC-MS is used for nonvolatile compounds with higher molecular weight, both polar and nonpolar, while CE is mainly used for polar, charged analytes. Nowadays, these techniques are routinely used in many fields such as clinical biochemistry [13-15], pharmacy [16], food science [17], environmental analyses [6,18], toxicology [19,20], and forensics [21,22], to list a few
Optimization of the isocratic separation of dithranol and related compounds by reversed-phase liquid chromatography
No full textAn optimum mobile-phase composition is proposed for resolution of the impurities in dithranol and compounds related to dithranol by isocratic reversed-phase HPLC in a single run. A combination of Snyder's solvent selectivity triangle concept with mixture design was used to achieve this goal. The quantification of the five substances involved was tested and the ruggedness of the method verified for small changes in the mobile phase composition
Determining orthogonal and similar chromatographic systems from the injection of mixtures in liquid chromatography-diode array detection and the interpretation of correlation coefficients color maps
No full textGeneric orthogonal chromatographic systems might be helpful tools as potential starting points in the development of methods to separate impurities and the active substance in drugs with unknown impurity profiles. The orthogonality of 38 chromatographic systems was evaluated from weighted-average-linkage dendrograms and color maps, both based on the correlation coefficients between the retention factors on the different systems. On each chromatographic system, 68 drug substances were injected as mixtures of three or four components to increase the throughput. The (overlapping) peaks were identified and resolved with a peak purity algorithm, orthogonal projection approach (OPA). The visualization techniques applied allowed a simple evaluation of orthogonal and (groups of) similar systems.</p
Optimisation of the isocratic separation of dithranol and related compunds by Reversed Phase Liquid Chromatography
No full textAntioxidant and anticandidal activities of the Tunisian Haplophyllum tuberculatum (Forssk.) A. Juss. essential oils
No full textHaplophyllum tuberculatum Forssk. is a medicinal plant growing in Tunisia. It is widely used in traditional medicine against gastro-intestinal problems, fevers, ear infections and rheumatisms. The present investigation evaluated the effects of leaves, stems and leaves + stems essential oils of Haplophyllum tuberculatum Forssk. and of their pure compounds on free radicals as well as their anticandidal activities. Screening for the antioxidant activity of the oils, R-(+)-limonene, S-(−)-limonene and 1-octanol was conducted by DPPH, ABTS and β-carotene/linoleic acid radical scavenging assays. The essentials oils and their compounds were screened for antifungal activity against four Candida species: Candida albicans ATCC 90028; Candida glabrata ATCC 90030; Candida parapsilosis ATCC 27853 and Candida krusei ATCC 6258. When compared with ascorbic acid as standard, it was found that the essential oils have a significant inhibition in scavenging free radicals, resulting in an important IC50. The pure compounds were inactive against the free radicals. The anticandidal test results showed that leaves, stems and leaves + stems oils strongly inhibited the growth of Candida krusei at 30 μg/mL leaves oils and 70 μg/mL for other oils and that moderately of the 3 other Candida species. The pure compound, 1-octanol, was active one against the candida species, with MIC-values between 0.07 and 1.25 mg/mL.
In all in vitro assays, a significant correlation existed between the concentrations of the essential oils, the percentage inhibition of free radicals and of the growth inhibitory of tested candida species. The results indicate the essential oils may be applied for treating diseases related to free radicals, potentially to prevent cancer development and as an antifungal agent against Candida
The application of Kohonen neural networks to diagnose calibration problems in atomic absorption spectrometry
No full textNegocios Inclusivos – Modelos Empresariales Incluyentes. Conceptos, Casos y Perspectivas para la Alianza de Aprendizaje.
No full textEste documento hizo parte de la sesión 2 (Modelos de Vinculación de Productores Pobres Mediante Negocios Inclusivos) del Taller Regional de Intercambio de la Alianza de Aprendizaje, realizado en junio de 2010, y presenta el concepto de Negocios Inclusivos (Qué son, Cuáles son sus beneficios para la empresa y para las comunidades pobres), Cómo implementa el Servicio Holandés de Cooperación al Desarrollo (SNV) este modelo de negocio y cuáles han sido sus principales lecciones aprendidas; así como algunos casos de aplicación y un mapeo regional de intervenciones en negocios inclusivos
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