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M N Myers

Publications and source records attributed to M N Myers.

5 recordsLinked to original sources
PubMed1991

Hydrodynamic relaxation in flow field-flow fractionation using both split and frit inlets.

Two means are described for achieving hydrodynamic relaxation and thus avoiding the stopflow injection procedure in field-flow fractionation (FFF): split flow injection and frit inlet injection. The advantages, disadvantages, and the theoretical basis of these procedures are discussed. Incremental band broadening due to the final relaxation step is examined theoretically and shown to be negligible when the flow rate of the sample inlet substream is small compared to the total channel flow rate. The optimization of the sample inlet flow rate is discussed. Experimental results for both injection procedures are reported for flow/steric (or hyperlayer) FFF applied to latex standards, confirming the expected trends. However, closer examination shows that the observed incremental band broadening associated with hydrodynamic relaxation is somewhat larger than the value predicted.

Chemical Phenomena↗
PubMed1991

Particle size distribution by sedimentation/steric field-flow fractionation: development of a calibration procedure based on density compensation.

Because of the important but mathematically complex role played by hydrodynamic lift forces in sedimentation/steric FFF, applied generally to particles greater than 1 micron in diameter, retention cannot readily be related to particle diameter on the basis of simple theory. Consequently, empirical calibration is needed. Unfortunately, retention is based on particle density as well as size so that a purely size-based calibration (e.g., with polystyrene latex standards) is not generally valid. By examining the balance between driving and lift forces, it is concluded that equal retention will be observed for equal size particles subject to equal driving forces irrespective of particle density. Therefore by adjusting the rotation rate to exactly compensate for density, retention can be brought in line with that of standards, a conclusion verified by microscopy. Linear calibration plots of log (retention time) versus log (diameter) can then be used. This approach is applied to two glass bead samples (5-30 and 5-50 microns) using both a conventional and a pinched inlet channel. The resulting size distribution curves are self consistent and in good agreement with results obtained independently.

Calibration↗
PubMed1977

Flow field-flow fractionation: new method for separating, purifying, and characterizing the diffusivity of viruses.

The nature and theory of flow field-flow fractionation is described, and its potential applicability to virus-like particles is discussed. Different virus types are shown to be retained at different levels. Retention can be controlled by variation of the experimental parameters, in good agreement with theory. However, a mild adsorption effect is indicated and requires the development of alternate strategies for measuring diffusion coefficients. For Qbeta, our value agrees well within 10% of literature values; the values obtained for other viruses, using Abeta as an internal standard, are untested. Finally, it is demonstrated that flow field-flow fractionation can cleanly fractionate two viruses from one another and from an albumin impurity, that samples as large as several milligrams in size can be analyzed, and that the method has potential utility in the quantitative and qualitative analysis of virus systems.

Albumins↗
PubMed1976

Flow-field-flow fractionation: a versatile new separation method.

Flow-field-fractionation is a new separation technique that seems likely to have broad applicability. Its theoretical scope includes any solute for which one can find a solvent and a semipermeable membrane. The principles on which the technique is based are presented. Some experiments with polystyrene beads, viruses, and proteins verify that retention depends solely on diffusion coefficients.

Chemical Fractionation↗