E.i. Dupont De Nemours and Company

Other

Wallace W Yau

Joseph J Kirkland

Charles H Dilks, Jr

Scot D Abbott

John W Grant

There is disclosed apparatus and method for determining molecular weight by osmometry. A fluid circuit is used having two pressure measurement zones, one responsive only to viscosity effects and the other to both viscosity and osmotic effects. The osmotic effects are caused by cross-linked polymeric material within one zone capable of expanding and contracting in response to the presence of a solvent and a solution, respectively, thereby changing the effective radius of the zone and hence the pressure.

Osmotic method for determining the molecular weight of solutes in

A method for measuring the inherent viscosity of individual solute components in a multicomponent sample in solution with a solvent comprising for each component (1) measuring pressure differences for solvent and for solvent with solute component, as a function of time across two capillary tubes in fluid communication (2) measuring concentrations of component as a function of time, and (3) obtaining inherent viscosity by means of a described mathematical relationship.

Viscosity detection method for liquid chromatography systems with

An improved differential pressure capillary viscometer in which a sample of solute in solution with a solvent is introduced into a stream of flowing solvent. The sample passes sequentially into first and second capillary tubes in which pressure differences are measured as a function of time. The pressure differences can be related to the viscosity of the sample.

Differential pressure capillary viscometer

A means for measuring either the intrinsic or inherent viscosity of a solute in solution with a solvent which is independent of flow rate and temperature fluctuations. The solution is passed through one capillary tube and the solvent through a second capillary, and the pressure drop across each is measured. Signals corresponding to each pressure drop measurement are fed to an amplification means such as a logarithmic amplifier where they are processed to determine either the intrinsic or inherent viscosity of the solute independent of flow rate and temperature fluctuations. The viscosity measuring means may also be used together with size exclusion chromatrography to determine the molecular weight distribution of polymer materials. It may also be used to measure the relative viscosity of a sample liquid and a reference liquid, and to determine the viscosity of the sample liquid independent of flow rate and temperature fluctuations.

Differential pressure capillary viscometer for measuring viscosity

A means for measuring either the intrinsic or inherent viscosity of a solute in solution with a solvent which is independent of flow rate and temperature fluctuations. The solution is passed through one capillary tube and the solvent through a second capillary, and the pressure drop across each is measured. Signals corresponding to each pressure drop measurement are fed to a logarithmic amplification means where they are processed to determine either the intrinsic or inherent viscosity of the solute independent of flow rate and temperature fluctuations. The viscosity measuring means may also be used together with size exclusion chromatrography to determine the molecular weight distribution of polymer materials. It may also be used to measure the relative viscosity of a sample liquid and a reference liquid, and to determine the viscosity of the sample liquid independent of flow rate and temperature fluctuations.

A plastic ring has a circumferential groove formed in its outer peripheral surface. The ring is fitted in a bowl-type centrifuge rotor such that the ring's outer surface contacts the inner wall of the rotor. The channel is defined by the groove and rotor wall. The rotor is filled with a compensating liquid to reduce centrifugal stress on the plastic and to reduce leakage from the channel.

Apparatus and method for sedimentation field flow fractionation

A free floating plastic channel for sedimentation field flow fractionation is suspended in a centrifuge rotor filled with a compensating liquid. The channel is constructed of a plastic central hub assembly fitted with a plastic outer ring preferably of a lower density than the hub. The hub contains a shallow channel on its outer surface and is interference-fitted to the outer ring to insure a liquid tight seal at zero force field. With the liquid totally surrounding the hub-outer ring assembly, stresses on the plastic parts are essentially equalized even under high force fields and leakage from the channel at the hub-ring interface is greatly reduced.

Sedimentation field flow fractionation channel and method

The method described is useful in field flow fractionation techniques for reducing separation times and improving the convenience and accuracy of measuring sizes or molecular weights of particulates. In field flow fractionation, the particulates (particles or macromolecules) are subjected to a force field and a mobile phase while passing through a flow channel. This field strength is decreased exponentially as a function of time. Alternatively the flow velocity is increased exponentially as a function of time. The initiation of the change in field strength or flow velocity may be delayed a period of time. If this time delay is made equal to the time constant of the exponential decay, the range of particulate retention time that is linearly related to the logarithm of the particle size or molecular weight is increased. An apparatus for implementing the method is also described and teaches the use of a function generator for providing the desired exponential decay and delay time. The apparatus is described in implementations involving a force field.

Method and apparatus for field flow fractionation

A long, thin annular belt-like channel is designed for use in sedimentation field flow fractionation. The channel has a generally rectangular cross section and a width to thickness aspect ratio lying in the range of 3-50 to 1. The channel may be formed of a flattened capillary tube. The ratio of the thickness of the channel to the characteristic height of the particles to be separated is greater than 5 to 1.

Rotor for sedimentation field flow fractionation

A long, thin annular belt-like channel is designed for use in sedimentation field flow fractionation. This channel, which may be contained in the rotor of a centrifuge, has a generally rectangular cross-section. It has an inlet positioned to introduce particulates (includes particles and/or macromolecules) approximately at the radial distance from the outer wall that is the equilibrium distance resulting from the average force field exerted on each particulate by the centrifugal force field and by the opposing normal diffusion forces due to Brownian motion. An outlet for the channel is similarly located. A modified design tapers the inlet and outlet.

Apparatus for field flow fractionation

Disclosed herein is a resolving zone for a chromatograph comprising a plurality of porous, silica macroparticles chosen to provide the resolving zone with a bimodal pore distribution, the average pore size for each mode being such that the linear portions of the molecular weight calibration curve for each pore size in the bimodal distribution are nonoverlapping and the pore volume of each mode being such that the aforesaid linear portions are substantially parallel. The macroparticles can be either totally or superficially porous. The resolving zone can be composed of either a plurality of macroparticles each having a bimodal pore distribution or a plurality of macroparticles having one pore size distribution and a plurality of macroparticles having another pore distribution.

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Wilmington, DE, United States of America

Wallace W Yau