RESUMO
The UHPLC strategy which combines sub-2 microm porous particles and ultra-high pressure (>1000 bar) was investigated considering very high resolution criteria in both isocratic and gradient modes, with mobile phase temperatures between 30 and 90 degrees C. In isocratic mode, experimental conditions to reach the maximal efficiency were determined using the kinetic plot representation for DeltaP(max)=1000 bar. It has been first confirmed that the molecular weight of the compounds (MW) was a critical parameter which should be considered in the construction of such curves. With a MW around 1000 g mol(-1), efficiencies as high as 300,000 plates could be theoretically attained using UHPLC at 30 degrees C. By limiting the column length to 450 mm, the maximal plate count was around 100,000. In gradient mode, the longest column does not provide the maximal peak capacity for a given analysis time in UHPLC. This was attributed to the fact that peak capacity is not only related to the plate number but also to column dead time. Therefore, a compromise should be found and a 150 mm column should be preferentially selected for gradient lengths up to 60 min at 30 degrees C, while the columns coupled in series (3x 150 mm) were attractive only for t(grad)>250 min. Compared to 30 degrees C, peak capacities were increased by about 20-30% for a constant gradient length at 90 degrees C and gradient time decreased by 2-fold for an identical peak capacity.
Assuntos
Cromatografia Líquida/métodos , Modelos Químicos , Pressão , Acetonitrilas , Algoritmos , Apigenina/isolamento & purificação , Ácidos Cumáricos/isolamento & purificação , Cinética , Lanatosídeos/isolamento & purificação , Peso Molecular , Rutina/isolamento & purificação , TemperaturaRESUMO
An analytical method for the determination of cardiac glycosides in Digitalis purpurea leaves by hplc was developed. Quantitation was carried out by the incorporation of lanatoside A as an internal standard. The present method is sufficiently precise and relatively simple.
Assuntos
Glicosídeos Cardíacos/análise , Glicosídeos Digitálicos/análise , Digitalis/química , Folhas de Planta/química , Plantas Medicinais , Plantas Tóxicas , Cromatografia Líquida de Alta Pressão , Hidrólise , Lanatosídeos/química , Lanatosídeos/isolamento & purificaçãoRESUMO
A rapid extraction method followed by high-performance liquid chromatographic assay was developed for the quantitative determination of the cardioactive glycosides of Digitalis lanata. The leaf samples were extracted with water or aqueous alcohols. The simple extraction method gives a better yield than the methods described previously. Lanatoside C and its metabolites have been separated on a reversed-phase column with various mixtures of acetonitrile, methanol, and water as mobile phases for isocratic elution. Extraction and quantitative determination of lanatoside C and digoxin from a leaf sample require not more than 30 min.
