Measuring and testing – Specimen stress or strain – or testing by stress or strain... – By loading of specimen
Reexamination Certificate
1999-12-23
2001-02-27
Raevis, Robert (Department: 2856)
Measuring and testing
Specimen stress or strain, or testing by stress or strain...
By loading of specimen
Reexamination Certificate
active
06192764
ABSTRACT:
BACKGROUND OF THE INVENTION
1. The Field of the Invention
The present invention relates generally to analytical separation techniques such as field-flow fractionation. More specifically, the present invention relates to a method and a device for introducing samples in analytical separation apparatuses, and in particular to field-flow fractionation systems.
2. Related Application
This is a division of application Ser. No. 09/032,188, filed Feb. 27, 1998, on behalf of Yong Jiang, Ph.D., Marcia Elaine Hansen, Ph.D., Michael Eliot Miller, Ph.D., and Andreas Martin Kummerow, entitled Sample Focusing Device and Method, which is hereby incorporated herein by reference.
3. Present State of the Art
Field-flow fractionation is a separation and characterization technique that relies on the effects of an applied field on a sample that is carried by a fluid flow. This fluid flow moves down a channel that will hereinafter be referred to as the “channel”. The stream flowing along the channel will be referred to by the term “channel flow”.
The character and strength of the interaction between the species in the sample 15 and the field plays a decisive role in the separation. Species that more weakly interact with the field are more rapidly carried away by the fluid flow that moves perpendicular to the applied field. This leads to different retention times for different species in the sample. Field-flow fractionation was disclosed in U.S. Pat. No. 3,449,938, and it is an excellent technique to separate and characterize a great variety of species. Field-flow fractionation is also known as single phase chromatography, polarization chromatography and capillary hydrodynamic fractionation. These species include cells, subcellular particles, viruses, liposomes, protein aggregates, fly ash, colloids, industrial lattices and pigments, polymers, humic materials, proteins, and nucleic acid molecules such as DNA. Some of these species are dissolved in the fluid flow that carries the sample, whereas other species are better characterized as being suspended in the fluid flow. Consequently, the terms “carrier fluid” and “carrier” will hereinafter refer to the fluid flow that transports the sample species, regardless of the form in which such species are contained in the fluid medium (i.e., whether dissolved, dispersed, suspended or in any other form of aggregation in the fluid flow). Furthermore, terms such as “sample species”, “particles” or “particle”, and “component” or “components”, will hereinafter characterize the entity or entities in the sample to be analyzed, or more particularly, in the sample that contains the entities to be separated. More particularly, these terms used in the specific context of field-flow fractionation refer to any sample species that can be retained and separated by any field-flow fractionation method, including rigid and deformable particles ranging in size from submicron to hundreds of microns, polymer molecules, aggregates and clusters, biological macromolecules, and particles including cells, DNA, proteins and any other molecules that are capable of analysis by field-flow fractionation. Consequently, these terms refer to the entities or components in the sample that is to be analyzed or separated, regardless of the nature, mass, size or any other specific characteristic of these entities, and the sample to be analyzed or separated is hereinafter referred to as the “sample”.
The great variety of sample species that can be separated and characterized by field-flow fractionation makes this technique an important tool for solving problems in a plurality of fundamental and applied research areas that include biology, medicine, and material and environmental sciences. More specifically, field-flow fractionation has been applied to sample species whose masses span a 10
15
-fold range. These species encompass molecules with a mass of about 600 Dalton and increasingly bigger entities up to particles of about 100 micrometers in diameter.
The choice of the applied field in field-flow fractionation depends on the particular property that controls the retention time of the sample species that is to be separated. The types of applied fields that can be used in implementing field-flow fractionation include thermal, gravitational, electric, and magnetic gradients. In addition, a cross flow with respect to the carrier is also used in flow field-flow fractionation, a very versatile and effective implementation of the field-flow fractionation principles. Other types of applied fields that have in fact been applied or that are of potential practical relevance as a driving force in field-flow fractionation include forces due to dielectrical, concentration gradient, photophoretic and shear effects. A short-hand notation that consists of the acronym FFF preceded by the name of the applied field is used hereinafter. Available commercial types of field-flow fractionation include flow FFF, thermal FFF, and sedimentation FFF. These types differ by the type of applied field. In flow FFF, the field that drives separation is a flow stream directed perpendicular to the channel flow longitudinal axis. A method and apparatus for flow FFF is described in U.S. Pat. No. 4,147,621. In thermal FFF, a thermal gradient is used as the field to drive separation. Acceleration is used to drive separation in sedimentation FFF. In particular, this acceleration is that of a centrifugal field in sedimentation FFF, and it is the gravitational field in gravitational FFF. Unless otherwise specified, the terms “field” or “applied field” will hereinafter refer to any applied field, to a cross flow, and to any appropriately generated potential gradient that creates a driving force that directs the sample species into a wall of the channel called the accumulation wall. Furthermore, the examples and illustrations offered herein refer in particular to flow FFF because this field-flow fractionation technique is currently established as a very versatile and effective technique. In addition, flow FFF has been characterized as the most universal of the field-flow fractionation methods. J. Calvin Giddings,
Field
-
Flow Fractionation, Chemical and Engineering News
, Vol. 66 (1988). pp.34-45; Particle Size Distribution II, ACS Symposium Series No. 472, S. Kim Ratanathanawongs, Inho Lee, and J. Calvin Giddings,
Separation and Characterization of
0.01-50-&mgr;
m Particles Using Flow Field
-
Flow Fractionation
, 1991, chapter 15, pp. 229-46.
For each applied field there are in turn a variety of operating modes. Each operating mode depends on the sample species separation mechanism. For example, sample species under the influence of an applied field may be subject to a diffusive, steric or hydrodynamic lift effects. Depending on which one of these effects is predominant, the field-flow fractionation operating mode is, respectively, a Brownian, steric or hyperlayer mode. Consequently, each appropriate choice of applied field and operating mode leads to a different field-flow fractionation subtechnique.
Whereas sample species separation according to mass or size is often the goal of field-flow fractionation, this is not the only possible application of field-flow fractionation. With the appropriate choice of applied field, a field-flow fractionation apparatus can perform as a microbalance sensitive to forces of 10
16
N. Furthermore, field-flow fractionation permits the measurement of both particle size and density, from which a molar mass can be calculated. Other properties that can be calculated include particle diameter and charge. The high sensitivity of sedimentation FFF to very small amounts of adsorbed material permits the measurement of the mass and thickness of adsorbed layers. When the sample species population is heterogeneous in any of these properties, the different components are separated by field-flow fractionation on the basis of the heterogeneous property, and a distribution curve relative to this property is obtained. These and other background materials pertaining to field-flow fractionation have been described by Ro
Hansen Marcia E.
Jiang Yong
Kummerow Andreas M.
Miller Michael E.
FFFractionation, LLC
Raevis Robert
Workman & Nydegger & Seeley
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