Search results for "COMPOSITI"
showing 10 items of 2775 documents
Volatile compounds of flowers and leaves of Sideritis italica (Miller)Greuter et Burdet (Lamiaceae), a plant used as mountain tea
2010
Sideritis italica (Miller) Greuter et Burdet (Lamiaceae), widely used in ethnopharmacological medicine, occurs in Southern Italy and Sicily. The phytochemical composition of the essential oils of S. italica flowers and leaves, harvested in Piano Battaglia (Sicily), was analysed by GC and GC-MS. Of the 51 compounds, 43 in the oil from flowers and 29 in the oil from leaves were identified. Kaur-15-ene (20.0%) was recognised as the main constituent of the oil from flowers, together with beta-cubebene (12.1%), beta-pinene (8.5%), (Z)-nuciferol (6.5%), tricyclene (4.5%) and alpha-bisabolol (4.0%). In the oil from leaves, p-methoxyacetophenone (26.0%) prevailed, as did hexadecanoic acid (21.3%), …
Volatile components of Centaurea eryngiodes Lam. and Centaurea iberica Trev.var. hermonis Bois. Lam.,two Asteraceae growing wild in Lebanon.
2005
The volatile components of the flowerheads of Centaurea eryngioides Lam. and Centaurea iberica Trev. var. hermonis Boiss. Lam. were obtained by hydrodistillation and identified by GC and GC–MS. Altogether 91 components, mostly fatty acids and hydrocarbons, were identified.
Adsorptionsvoltammetrische Molybd�nbestimmung in biologischen Proben nach nassem Hochdruckaufschlu\
1989
The transfer of an (known from literature [141 and till now only applied to seawater) adsorption-voltammetric determination of molybdenum with oxine to biological samples, is described. The herewith accomplished changes of base solution resulted simultaneously in an optimization of the method with regard to interpretability and sensitivity. Special care was taken in the problem of decomposition. Best results are obtained with a high-pressure decomposition. Accuracy of analyses is confirmed with trials of recovery also in the biological matrix.
Gas chromatographic–mass spectrometric investigation of the chemical composition of beebread
2009
Beebread consumption has a very long tradition; however, its composition and bioactive properties have not been studied thoroughly up to now. This study is expected to expand the knowledge of chemical composition of this bee product as a natural remedy and functional food ingredient. With the help of successive extraction with organic solvents of different polarity, more than 200 compounds were extracted from five samples of beebread and then identified by GC-MS method. The content of some phenol compounds (p-coumaric acid, kaempherol, isorhamnetin) with antioxidant properties has been determined quantitatively. Different content of free aminoacids have been detected in the analyzed samples…
Towards the optimization of complementary systems in reversed-phase liquid chromatography
2002
Previously reported optimization methodology, which seeks complementary mobile phases (CMP) in isocratic chromatography, has been extended to include more than one system simultaneously (i.e. more than one organic solvent and/or column). In the literature the benefits of complementarity are not usually fully exploited—few working conditions giving rise to interactions as different as possible are examined, without developing a fully linked optimization. The proposed approach is compared critically with use of a single mobile phase or CMP which consider one system only. The strategy greatly expands the capability of isocratic chromatography in the analysis of complex samples that cannot be r…
A study on the essential oil of Ferulago campestris : How much does extraction method influence the oil composition?
2011
The essential oil of different parts of Ferulago campestris (Bess.) collected in Sicily has been extracted by microwave-assisted hydrodistillation (MAHD) and by classic hydrodistillation (HD). A comparative qualitative-quantitative study on the composition of the oils was carried out. A total of 100 compounds were identified in the oils obtained by MAHD, whereas 88 compounds characterized the HD oils. The most prominent components were, in all different parts of F. campestris and in both extraction methods, 2,4,5-trimethylbenzaldehyde and 2,4,6-trimethylbenzaldehyde isomers; the latter was not previously found. The attempt to evaluate where the oil components are located in all parts of the…
Free fatty acids and other volatile compounds for the characterisation of “Vastedda della valle del Belìce” cheese Acidos grasos libres y otros const…
2010
The analysis of the volatile constituents of “Vastedda della valle del Belice”, a typical Sicilian pasta filata cheese, was performed using solid phase microextraction and high-resolution gas chromatography/mass spectrometry. The research aimed to verify if the volatile fraction, determinant for cheese flavor, differs among producers and/or production seasons. The samples were provided by four producers from the area of the Protected Designation of Origin (PDO) production, during two different seasons of production. A total of 42 volatile components were identified: the main components were found to be butanoic, hexanoic, octanoic, and decanoic acid. Free fatty acids were quantified using t…
Evolution of phenolic compounds virgin olive oil during storage
1997
Phenolic compounds are of fundamental importance to the shelf life of virgin olive oils because of their antioxidative properties. In this paper, the evolution of simple and complex olive oil phenols during 18 mon of storage is studied by high-performance liquid chromatography (HPLC) analysis. The olive oils under examination were from various olive cultivars, harvested in two sectors in the same region at different stages of ripeness. The findings indicate that it is not the variety but rather the ripeness of the olives and the soil and climate that influence the phenol composition of virgin olive oil. In addition, a positive correlation was found between the age of the oils and the tyroso…
High-performance liquid chromatographic determination of Maillard compounds in store-brand and name-brand ultra-high-temperature-treated cows' milk.
2000
Furosine and furfural products of the Maillard reaction are used as specific indicators of the effect of heating treatments on milk quality. Their contents were measured in representative samples of store- and name-brand ultra-high-temperature-treated milks using RP-HPLC with UV detection. Furosine contents ranged from 40.32 to 50.67 and from 65.48 to 310.58 mg/100 g protein in name- and store-brand milks, respectively. Of the furfurals, only hydroxymethylfurfural was detected. The free hydroxymethylfurfural contents of store-brand milks ranged from 0.22 to 1.70 mg/100 g protein. Total hydroxymethylfurfural contents ranged from 0.29 to 0.41 and from 0.72 to 2.21 mg/100 g protein, for name- …
Robust interpretive optimisation in high-performance liquid chromatography considering uncertainties in peak position.
2005
In the context of interpretive chromatographic optimisation, robustness is usually calculated by introducing deliberated shifts in the nominal optimal conditions and evaluating their effects on the monitored objective function, mimicking thus the experimental procedures used in method validation. However, such strategy ignores a major source of error: the uncertainties associated to the modelling step, that may give rise to deceiving results when conditions that were expected to yield baseline separation are reproduced in the chromatograph. Two approaches, based on the peak purity concept, are here proposed to evaluate the robustness of the objective function under the perspective of measur…