Time-based retention ratio for curved separation channels: Application to sedimentation field-flow fractionation
✍ Scribed by Michel Martin
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 83 KB
- Volume
- 9
- Category
- Article
- ISSN
- 1040-7685
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✦ Synopsis
A new general expression of the ratio of the void time to analyte retention time, which one calls the time-based retention ratio R , is given for t curved separation channels. It differs from the classical definition of the retention ratio, based on a velocity ratio, which does not account for the fact that the length of the separation channel along the flow direction is shorter in regions near the curvature axis than in regions far from this axis. This new definition is applied in Ž . sedimentation field-flow fractionation FFF . The deviations of the velocity profile from the parabolic shape due to the channel curvature and of the concentration profile from the exponential distribution due to the variation of the centrifugal force within the channel thickness are taken into account. The deviation of R t from the classical retention ratio appears to be of the order of magnitude of the curvature ratio ␦ , defined as the ratio of the channel thickness to the radius of the outer wall. A polynomial development of R limited to the first order in ␦ is t obtained and seen to converge toward the classical FFF retention equation for vanishingly small ␦ s. It can be used for precise retention time prediction or analyte characterization.