Density gradients in packed columns: II. Effects of density gradients on efficiency in supercritical fluid separations

Baker, L. Robert; Orton, Andrew W.; Stark, M.A.; Goates, Steven R.

doi:10.1016/j.chroma.2009.05.078

Cited by 9 publications

(6 citation statements)

References 31 publications

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“…As a related side note, in the earlier studies [6][7][8] in which we first noticed an effect of packing on signal intensity, measurements were made through windows in the polyimide coating on the microcapillary columns, but the overall optical arrangement was different than in this study, and the signal light was imaged on the slit of a monochromator, so the observation volume was well defined. However, at that time, we did not attempt to quantitatively compare the difference between signals from packed and unpacked columns.…”

Section: Resultsmentioning

confidence: 82%

“…[1][2][3][4] As an example, smaller sample volumes allow reduced dead volumes in flowing systems and thereby limit the spread of bands flowing through a detection cell. 5 We observed enhanced detection in a previous series of studies [6][7][8] of the flow of supercritical fluids in microcapillary columns (250 mm i.d.) packed with 5 mm diameter silica particles.…”

Section: Introductionmentioning

confidence: 85%

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Enhanced Fluorescence in a Scattering Medium

2021

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Often only small amounts of sample are available for spectroscopic analytical determinations. This work investigates the enhancement of signal in columns packed with silica particles. We propose that silica particles cause the light to scatter through the column, effectively increasing optical path length. Packed columns are shown to be effective with fluorescence spectroscopy, but results were inconclusive with absorbance spectroscopy.

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Section: Resultsmentioning

confidence: 82%

Section: Introductionmentioning

confidence: 85%

Enhanced Fluorescence in a Scattering Medium

2021

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“…While such sub‐cm columns are not yet available in the marketplace, the creation of such products could be feasible. It is important to point out that equation (4),

t_{min cc} = t_{2, S} {(), (\frac{R st}{R si})}^{2},

does not take into account the pressure‐induced changes in mobile phase density along the length of the column under SFC conditions that will lead to small deviations from the predicted retention value as the column is shortened. In addition, the t min cc equation does not take into account the residence time due to extracolumn volume, a factor that can often be neglected for conventional sized columns, but that becomes significant as the size of the column decreases .…”

Section: Resultsmentioning

confidence: 99%

Pushing the speed limit in enantioselective supercritical fluid chromatography

Regalado

Welch

2015

J. Sep. Science

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Chromatographic enantioseparations on the order of a few seconds can be achieved by supercritical fluid chromatography using short columns packed with chiral stationary phases. The evolution of 'world record' speeds for the chromatographic separation of enantiomers has steadily dropped from an industry standard of 20-40 min just two decades ago, to a current ability to perform many enantioseparations in well under a minute. Improvements in instrument and column technologies enabled this revolution, but the ability to predict optimal separation time from an initial method development screening assay using the t(min cc) predictor greatly simplifies the development and optimization of high-speed chiral chromatographic separations. In this study, we illustrate how the use of this simple tool in combination with the workhorse technique of supercritical fluid chromatography on customized short chiral columns (1-2 cm length) allows us to achieve ultrafast enantioseparations of pharmaceutically relevant compounds on the 5-20 s scale, bringing the technique of high-throughput enantiopurity analysis out of the specialist realm and into the laboratories of most researchers.

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“…The ratio of diffusion in the particles versus the molecular diffusion, D part /D mol , was set at a value of 0.4. For the calculation of the dependence of the molecular diffusion coefficient, D mol (m 2 /s), on viscosity the Wilke-Chang equation was used [15][16][17][18]. The C-term coefficients were calculated as explained in [12].…”

Section: Plate Height Equationmentioning

confidence: 99%