کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
1204603 965160 2009 7 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Effect of an open tube in series with a packed capillary column on liquid chromatographic performance: The influence of particle diameter, temperature, and system pressure
موضوعات مرتبط
مهندسی و علوم پایه شیمی شیمی آنالیزی یا شیمی تجزیه
پیش نمایش صفحه اول مقاله
Effect of an open tube in series with a packed capillary column on liquid chromatographic performance: The influence of particle diameter, temperature, and system pressure
چکیده انگلیسی

A postcolumn reactor or a simple open tube connecting a capillary column to, for example, a mass spectrometer affects the performance of a capillary liquid chromatography system in two ways: stealing pressure from the column and adding band-spreading. This effect is especially intolerable in fast separations. Our calculations show that in the presence of a 25 μm radius postcolumn reactor, column (50 μm radius) efficiency (number of theoretical plates) is severely reduced by more than 75% with a t0 of 10 s and a particle diameter from 1 to 5 μm for unretained solutes at room temperature. Therefore, it is necessary to minimize the reactor's effect and to improve the column efficiency by optimizing postcolumn conditions. We derived an equation that defines the observed number of theoretical plates (Nobs) taking into account the two effects stated above, which is a function of the maximum pressure Pm, the particle diameter dp, the reactor radius ar, the column radius ac, the desired dead time t0, the column temperature T and zone capacity factor k″. Poppe plots were obtained by calculations using this equation. The results show that for a t0 shorter than 18 s, a Pm of 4000 psi, and a dp of 1.7 μm, a 5 μm radius reactor has to be used. Such a small reactor is difficult to fabricate. Fortunately, high temperature helps to minimize the reactor effect so that reactors with manageable radius (larger than 12.5 μm) can be used in many practical conditions. Furthermore, solute retention diminishes the influence of a postcolumn reactor. Thus, a 12.5 μm reactor supersedes a 5 μm reactor for retained solutes even at a t0 of 5 s (k″ > 3.8, or k′ > 2.0).

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Chromatography A - Volume 1216, Issue 9, 27 February 2009, Pages 1346–1352
نویسندگان
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