The Sorption Behavior of Alkyl Bonded Phases in Reverse-Phase, High Performance Liquid Chromatography

Lochmüller, C. H.; Wilder, D. R.

doi:10.1093/chromsci/17.10.574

Cited by 196 publications

(62 citation statements)

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“…Therefore Since L/u0 = t , at the column outlet, we obtain kakds )tm](20) km + k,(kd + k,)(2) Derivation of eq 21.-C,(x, d -s ) = d s therefore, when eq 19 is used p1 = (-1) lim Both 20 and 21 are verified. LITERATURE CITED (1) Chu, A. H.; Langer, S. H. Anal.…”

mentioning

confidence: 80%

Measurement of reaction rate constants in the liquid chromatographic reactor: mass transfer effects

Chu¹,

Langer²

1986

Anal. Chem.

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1817interactions to w ' -4 5 ' when w is in the range 40-120' and then it rotates back to w' -180' in the range w = 140-340'.The carboxylate also rotates along the Cl-C2 axis, and the ammonium slides from one face of the planar carboxylate to the other face. The motion of the isobutyl group in 9 is even more complex.The third and final point is that the calculations employed an effective dielectric constant oft = 1.50. This is reasonable for ionic CSP's in hydrocarbon solvent, but the results become less tenable for more polar solvents. Additionally, even though solvent molecules were not included in these calculations, explicitly including nonpolar organic solvents would not change the qualitative trends presented above.Our results are consistent with chemical intuition and highlight the fact that these ionic CSP's are even more conformationally flexible that one would a priori predict. Both syn and anti conformations exist, and the barrier to interconversion is small. Furthermore the pendant ammonium group plays a key role by coordinating with both the carboxylate and with the amide C=O. The conformational flexibility of the phenyl group in the phenylglycine CSP and the isobutyl group in the lycine CSP is great enough to allow for a wide range of orientations for templating purposes;perhaps it is this inherent flexibility that serves to make these CSP's so effective. We are currently investigating the conformational and dynamic behavior of the covalently bonded analogues and will report this at a later date.Registry No.The adaptation of llquid chromatographk c o h n s as chemkal reactors for r e a c t h klnetk studies Is examlned. The overall rate constants, k -, for pyrldlne and 4-plcollne catalyzed esteriflcatlon reactlons of tetrachloroterephthaloyl chlorlde were determined for a llquld chromatographk reactor (LCR). I t Is shown that wHh a rate constant for reactbn In the moMle phase, a valid rate constant for thls system can be obtalned for reactbn In the statlonary phase. Thus conversbns In each

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confidence: 80%

Measurement of reaction rate constants in the liquid chromatographic reactor: mass transfer effects

Chu¹,

Langer²

1986

Anal. Chem.

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“…This barrier may arise from the solvophobic collapse of the surface alkyl chains in the polar solvent, 63 requiring the surface alkyl chains to expand in order for DiI alkyl tails to intercalate. Intercalation of DiI is not possible on the C 1 surface, which would reduce the barrier to adsorption and thus lead to more rapid surface-association and interfacial diffusion.…”

Section: Emccd Camera (Details In Supporting Information)mentioning

confidence: 99%

Imaging Fluorescence-Correlation Spectroscopy for Measuring Fast Surface Diffusion at Liquid/Solid Interfaces

Cooper

Harris

2014

Anal. Chem.

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The development of techniques to probe interfacial molecular transport is important for understanding and optimizing surface-based analytical methods including surface-enhanced spectroscopies, biological assays, and chemical separations. Single-molecule-fluorescence imaging and tracking has been used to measure lateral diffusion rates of fluorescent molecules at surfaces, but the technique is limited to the study of slower diffusion, where molecules must remain relatively stationary during acquisition of an image in order to build up sufficient intensity in a spot to detect and localize the molecule. Although faster time resolution can be achieved by fluorescence-correlation spectroscopy (FCS), where intensity fluctuations in a small spot are related to the motions of molecules on the surface, long-lived adsorption events arising from surface inhomogeneity can overwhelm the correlation measurement and mask the surface diffusion of the moving population. Here, we exploit a combination of these two techniques, imaging-FCS, for measurement of fast interfacial transport at a model chromatographic surface. This is accomplished by rapid imaging of the surface using an electron-multiplied-charged-coupled-device (CCD) camera, while limiting the acquisition to a small area on the camera to allow fast framing rates. The total intensity from the sampled region is autocorrelated to determine surface diffusion rates of molecules with millisecond time resolution. The technique allows electronic control over the acquisition region, which can be used to avoid strong adsorption sites and thus minimize their contribution to the measured autocorrelation decay and to vary the acquisition area to resolve surface diffusion from adsorption and desorption kinetics. As proof of concept, imaging-FCS was used to measure surface diffusion rates, interfacial populations, and adsorption-desorption rates of 1,1'-dioctadecyl-3,3,3'3'-tetramethylindocarbocyanine (DiI) on planar C18- and C1-modified surfaces.

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“…Pairs typically used for this purpose are ethylbenzene/toluene or amylbenzene/butylbenzene [10][11][12][13][14][15][16][17].…”

Section: Introductionmentioning

confidence: 99%

Three methods to characterize reversed phase liquid chromatographic columns applied to pharmaceutical separations

Németh

Haghedooren

Noszál

et al. 2008

Journal of Chemometrics

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Selecting a suitable reversed phase liquid chromatographic (RP-LC) column for a particular separation is complicated. More than 600 brands of C 18 columns are available on the market. Therefore, determining the characteristics influencing the selectivity of the different stationary phases is necessary. In this paper, three different methods to characterize RP-LC columns are compared. Hoogmartens et al. developed a column characterization system based on test methods from literature, which were reduced with principal component analysis (PCA), and led to four final chromatographic parameters. The second method studied is this of Euerby et al. who developed a column classification system using six parameters, based on the method of Tanaka and also applying PCA. The third method, developed by Snyder et al. is different from the other two. It uses five parameters, calculated by multiple linear regression from the retention data of 18 solutes. The suitability of the column classification systems was examined on pharmaceutical separations. It seems that all three methods can facilitate the selection of a suitable column for an analysis.

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The Sorption Behavior of Alkyl Bonded Phases in Reverse-Phase, High Performance Liquid Chromatography

Cited by 196 publications

References 0 publications

Measurement of reaction rate constants in the liquid chromatographic reactor: mass transfer effects

Measurement of reaction rate constants in the liquid chromatographic reactor: mass transfer effects

Imaging Fluorescence-Correlation Spectroscopy for Measuring Fast Surface Diffusion at Liquid/Solid Interfaces

Three methods to characterize reversed phase liquid chromatographic columns applied to pharmaceutical separations

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