Chemical apparatus and process disinfecting – deodorizing – preser – Physical type apparatus – Means separating or dissolving a material constituent
Reexamination Certificate
2000-07-06
2003-05-13
Warden, Jill (Department: 1743)
Chemical apparatus and process disinfecting, deodorizing, preser
Physical type apparatus
Means separating or dissolving a material constituent
C422S068100, C422S081000, C422S082000, C422S255000, C436S161000
Reexamination Certificate
active
06562307
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus and a process for the simultaneous analysis of a plurality of samples containing colloidal particles by means of the field-flow fractionation method.
The field-flow fractionation method is a separation and measurement method which has already been known, for some time and goes back to J. C. Giddings and which is used in particular in the analysis of colloidal particles, for a number of polymers, for biological macromolecules and for a wide variety of polymer complexes [J. C. Giddings,
Anal. Chem.
67 (1995), 592A]. The field-flow fractionation method is often referred to as “one-phase chromatography” since the separation of the various particles to be separated takes place within a single phase. This phase is preferably a liquid phase.
The field-flow fractionation method profits from an essentially very simple analysis arrangement. The field-flow fractionation is preferably carried out within a narrow, shallow channel through which a constant stream of liquid is passed and maintained. A laminar flow profile is created here [Michel Martin,
Advances in Chromatography
(N.Y.), 1998, Vol. 39, 1-138]. As the second basic prerequisite for the performance of the field-flow fractionation method, a transverse force field or a transverse flow stream is superimposed on this flow profile. Through a combination of the laminar axial flow profile with the transversely superimposed force field or the transversely superimposed flow stream, samples containing different types of particle present in the carrier liquid can, utilizing the different effect of the resultant force field or flow stream on the different constituents of the samples, be divided spatially into precisely these different constituents. Fractionation takes place as a function of the hydrodynamic diameter (flow field-flow fractionation) or in other field-flow fractionation methods as a function of the chemical composition or density or charge, this usually being combined with the hydrodynamic diameter.
In general, a distinction can be made between four different techniques in the field-flow fractionation method, depending on the type of transversely applied force field. These are the following:
flow field-flow fractionation,
sedimentation field-flow fractionation,
thermal field-flow fractionation and
electrophoretic field-flow fractionation.
An example which may be mentioned is flow field-flow fractionation. In flow field-flow fractionation, a transverse flow stream of the carrier liquid takes on the role of the force field. With the aid of flow field-flow fractionation, the coefficient of friction of the particles to be analyzed, their hydrodynamic diameter and the diffusion coefficient can be determined directly from the following conditional equation chain:
F
flow stream
=fU=
3&pgr;&eegr;
d
h
U=
(
kT/D
)
U
where
f=coefficient of friction
U=transverse flow rate
&eegr;=viscosity
d
h
=hydrodynamic diameter
k=Boltzmann constant
T=absolute temperature
D=diffusion coefficient.
Some measurement inaccuracy in flow field-flow fractionation is caused by uneven wall surfaces or compressible membranes serving as accumulation wall. This is preferably countered by appropriate calibration by means of a known diffusion coefficient or particularly preferably by coupling flow field-flow fractionation with one or more on-line detector(s).
Besides the parameters obtainable directly, further parameters, for example the molecular weight or gyration radii of polymers, can also be determined by means of appropriate models, assumptions or other prior knowledge regarding the particles to be analyzed.
Hitherto, when applying the field-flow fractionation method to the analysis of a sample, use has always been made of only a single separation channel, into which the sample was injected, transported through the channel by the carrier liquid and divided into individual zones, as explained above, during passage through the channel, depending on the choice of the specific field-flow fractionation method, these zones then ultimately allowing information to be provided on the individual particles present in the sample to be analyzed. Besides the separation channel, this required an extensive set of further peripherals, for example, inter alia, a pump for the carrier liquid, a further pump for the injection of the sample to be analyzed into the separation channel, depending on the analysis aim at least one detector or a further measurement or analysis unit coupled to the separation channel. Suitable detectors are, for example, all detectors from gel permeation chromatography (GPC), for example refractive index detectors (RI detectors), infra-red detectors (IR detectors), UV-VIS detectors, fluorescence detectors, light scattering detectors, Raman detectors, MALDI detectors and evaporation light scattering detectors. Furthermore, a storage container for the carrier liquid is provided. In addition, high quality demands are made of the separation channel, for example the requirement for an extremely pressure-stable construction so that the liquid streams remain stable in the narrow channels.
If, for example, the flow field-flow fractionation method is considered for the determination of the size distribution of colloidal particles in a sample to be analyzed, the procedure adopted hitherto was to inject in each case one sample into a separation channel coupled to a corresponding set of peripherals. The separation channel corresponded to a shallow channel, typically with a length of from about 1 cm to 100 cm and a depth in the range from about 0.1 mm to 0.4 mm. At least one of the walls delimiting the channel was a semi-permeable membrane, which was permeable to the carrier liquid, but impermeable to the particles present in the sample. After injection of the sample into the separation channel, the sample was firstly focused on an area inside the separation channel. This is achieved, for example, by pumping the carrier liquid into the channel from both ends of the channel, i.e. both from the inlet and from the future outlet, immediately after injection of the sample, so that the sample is initially concentrated in an area within the channel. Due to the action of the transverse flow stream as employed in flow field-flow fractionation, the sample or the particles present therein is transported in the direction of the accumulation wall, which corresponds here to the semi-permeable wall, and is initially concentrated there. The diffusion motion of the particles then commences in the opposite direction to the transverse flow stream and to different degrees depending on the particle type and/or size. When an equilibrium has been reached between the transverse flow stream and the corresponding diffusion motion, the respective particles come to a “stop” at a certain point or in a certain, particle-dependent zone within the channel cross section; the particles have then reached their equilibrium position with respect to transverse motion. Depending on the position within the cross section, they are then transported through the channel at different speeds by the carrier liquid, which is pumped into the channel from the inlet side of the separation channel with a flow profile which is not uniform with respect to the channel cross section, i.e. the various particles have different residence times within the separation channel. The residence time as an actual parameter ultimately allows conclusions to be drawn on the respective forces acting on the particles within the channel, taking into account the known non-uniform flow profile of the carrier liquid, as explained above, and in turn, according to the abovementioned conditional equilibrium chain, allows information to be obtained on specific parameters, for example the hydrodynamic diameter. The duration of the measurement for particles of a single type is in the range from less than one minute to about 2 hours, depending on the sample type and on the structure
Schrof Wolfgang
Schuch Horst
BASF - Aktiengesellschaft
Gakh Yelena
Keil & Weinkauf
Warden Jill
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