Fast analysis in liquid chromatography using small particle size and high pressure

Abstract

ReviewFast analysis in liquid chromatography using small particle size and high pressureIn order to enhance chromatographic performances in terms of efficiency and rapidity, LC has recently evolved in the development of short columns packed with small particles (sub-2 lm) working at high pressures (A400 bar). This approach has been described 30 years ago according to the fundamental chromatographic equations. However, systems and columns compatible with such high pressures have been introduced in the market in 2004 only. Advantages of small particles working at high pressure will be discussed in terms of sensitivity, efficiency, resolution, and analysis time. Potential problems encountered with high pressure in terms of frictional heating and solvent compressibility will also be discussed even if systems working at a maximum pressure of 1000 bar are not influenced by these parameters and give reliable and reproducible results. Several applications will highlight the potential and interest of this new technology.

O estado da arte da cromatografia líquida de ultra eficiência

“…Poucos anos mais tarde, surgiram as partículas esféricas porosas de 1,7 µm que, comparadas às partícu-las de 5 ou 3 µm, permitem melhores resoluções e altas eficiências, 30000 pratos/15 cm, porém, necessitam de uma instrumentação mais sofisticada para serem empregadas com o máximo de desempenho cromatográfico. [1][2][3][4] Os desenvolvimentos significativos alcançados na última década foram conseqüência do uso intenso da CLAE no mundo todo, como uma técnica de análise de rotina em laboratórios e, dessa forma, a busca por análises mais rápidas e com bom desempenho cromatográfico tornou-se evidente e necessária.…”

“…Esta alternativa foi aplicada, empregando-se partículas de FE de 3-3,5 µm, mas mesmo assim as separações apresentavam menor desempenho cromatográfico e perda de resolução. [4][5][6] Outra estratégia foi o uso das colunas monolíticas, 1,7,8 que são um meio contínuo de separação, comumente em formato cilíndrico, altamente poroso e preparadas a partir de sílica ou de material polimérico. A estrutura é caracterizada por apresentar macroporos (2 µm) e mesoporos (13 nm) que conferem aos monolitos eficiências similares às alcançadas com colunas recheadas com partículas de 3-3,5 µm, porém, oferecem uma permeabilidade maior que os materiais particulados e, dessa forma, podem ser usadas vazões mais altas sem aumento da pressão no sistema cromatográfico e sem perda de eficiência, devido à rápida taxa de transferência de massa.…”

An introduction to liquid chromatography–mass spectrometry instrumentation applied in plant metabolomic analyses

“…The fi nal signifi cant parameter is the pump pressure, which drives the mobile phase fl ow velocity. Generally as fl ow velocity increases, the effi ciency of chromatographic separation decreases, as does the analysis time, since the sample is being driven through the column more rapidly (Nguyen et al, 2006). This trend generally applies to columns that employ particle sizes of 3 µm and larger, however with sub-2 µm particles separation effi ciency is maintained with increasing mobile phase fl ow velocity (Fig.…”

“…Longer lengths of column enhance chromatographic separation, but at the expense of increased analysis times and system back pressure (Romanyshyn and Tiller, 2001). Smaller particle sizes lead to an increased surface area, thus improving compound retention and providing improved chromatographic separation at the expense of an increased pressure being required to drive the mobile phase (Nguyen et al, 2006;Novakova et al, 2006). The chromatographic separation effi ciency is commonly expressed as a theoretical plate value, with greater effi ciencies having greater theoretical plate values.…”

“…particle size result in greater system back pressures, as does increases in column length along with increased solvent consumption and sample analysis times (Romanyshyn and Tiller, 2001;Nguyen et al, 2006). In modern HPLC and UHPLC sub-2 µm particles are commonly employed to maximise the chromatographic resolution power along with short column lengths to reduce sample analysis times, backpressure, and solvent consumption (Novakova et al, 2006).…”