2 research outputs found
Introducing Enantioselective Ultrahigh-Pressure Liquid Chromatography (eUHPLC): Theoretical Inspections and Ultrafast Separations on a New Sub-2-μm Whelk-O1 Stationary Phase
A new chiral stationary phase for ultrahigh-pressure
liquid chromatography
(UHPLC) applications was prepared by covalent attachment of the Whelk-O1
selector to spherical, high-surface-area 1.7-μm porous silica
particles. Columns of varying dimensions (lengths of 50, 75, 100,
and 150 mm and internal diameters of 3.0 or 4.6 mm) were packed and
characterized in terms of permeability, efficiency, retention, and
enantioselectivity, using both organic and water-rich mobile phases.
A conventional HPLC Whelk-O1 column based on 5.0-μm porous silica
particles and packed in a 250 mm × 4.6 mm column was used as
a reference. Van Deemter curves, generated with low-molecular-weight
solutes on a 100 mm × 4.6 mm column packed with the 1.7-μm
particles, showed <i>H</i><sub>min</sub> (μm) and
μ<sub>opt</sub> (mm/s) values of 4.10 and 5.22 under normal-phase
and 3.74 and 4.34 under reversed-phase elution conditions. The flat
C term of the van Deemter curves observed with the 1.7-μm particles
allowed the use of higher-than-optimal flow rates without significant
efficiency loss. Kinetic plots constructed from van Deemter data confirmed
the ability of the column packed with the 1.7-μm particles to
afford subminute separations with good efficiency and its superior
performances in the high-speed regime, compared to the column packed
with 5.0-μm particles. Resolutions in the time scale of seconds
were obtained using a 50-mm-long column in the normal phase or polar
organic mode. The intrinsic kinetic performances of 1.7-μm silica
particles are retained in the Whelk-O1 chiral stationary phase, clearly
demonstrating the potentials of enantioselective UHPLC in terms of
high speed, throughput, and resolution
Postcolumn derivatization of amino acids using reaction flow chromatography columns with fluorescence detection: A fast new approach to selective derivatization techniques
<p>Reaction flow (RF) chromatography with fluorescamine reagent and fluorescence detection (FLD) was used for the analysis of amino acids. The performance of RF chromatography was tested against several optimized conventional postcolumn derivatization (PCD) methods. RF columns achieved greater sensitivity compared to conventional PCD methods, without the need for reaction loops, which resulted in more efficient separations. The RF-PCD method also achieved limits of detection (LOD) from the low picomole to subnanomole range. The calibration data of the RF-PCD technique yielded <i>R</i><sup>2</sup> ≥ 0.99 and % relative standard deviation in peak areas ranging from 0.34% to 5%. Through reaction flow chromatography, multiplexed detection was also achieved allowing the monitoring and analysis of derivatized and nonderivatized flow streams simultaneously.</p