JP4770603B2 - Field flow fractionation device - Google Patents

Description

  The present invention relates to a field flow fractionation apparatus for separating and separating fine particles contained in a fluid using field-flow fractionation, and more specifically, a cross using an asymmetric channel structure. The present invention relates to a flow type field flow fractionation apparatus.

  As a method for separating and detecting and sorting fine particles having a wide range of particle diameters of about 1 nm to 50 μm dispersed in a solution, a so-called cross flow type field flow fractionation ( Hereinafter, it is abbreviated as FFF) (see, for example, Patent Documents 1 and 2). First, the principle of this separation method will be briefly described with reference to FIGS.

  FIG. 7 is a perspective view showing an example of the basic structure of the separation channel of the crossflow type FFF, and FIG. 8 is a longitudinal sectional view of a part of the separation channel. As shown in FIG. 7, the separation channel 10 has a flat bottom wall surface 11 and an upper wall surface 12 which are disposed so as to face each other in the vertical direction, and a pair of side wall surfaces 13 and 14. An inlet port 15 and an outlet port 16 are provided at both ends of the flow path 17. As shown in FIG. 8, a large number of openings are formed in the upper wall surface 12, and the bottom wall surface 11 has a carrier solvent (fluid) placed inside a support wall 11 a formed with a large number of openings in the same manner as the upper wall surface 12. It has a structure in which a semipermeable membrane 11b that passes through and does not allow the fine particles to be separated to pass is in close contact. Here, the horizontal width (channel width) of the flow path 17 is constant at W, and the height of the flow path (channel height) is constant at H. As an example, the channel width W is about 1 to 2 cm, the channel height H is about several tens to 200 μm, and the length of the flow path 17, that is, the channel length L is about 20 to 30 cm.

  The carrier solvent is supplied from above to the separation channel 10 as described above so as to be orthogonal to the entire upper wall surface 12, thereby flowing into the flow path 17 through the opening of the upper wall surface 12, and semi-transparent to the bottom wall surface 11. A flow of the carrier solvent is formed so as to pass through the film 11b and pass downward through the opening of the support wall 11a. This carrier solvent flow F1 is called a cross flow. On the other hand, a carrier solvent in which fine particles to be separated are dispersed at a predetermined flow rate is introduced from the inlet port 15 into the separation channel 10, whereby the flow path 17 enters the flow path 17 from the left to the right as shown in FIG. A heading flow F2 is formed. This is a flow in which fine particles are conveyed from the inlet port 15 toward the outlet port 16, and is called an axial flow (or field flow or channel flow). The axial flow F2 and the cross flow F1 are substantially orthogonal to each other.

Since the cross flow F1 has a uniform flow velocity over the entire bottom wall surface 11 and the semipermeable membrane 11b does not pass the fine particles, the fine particles are located in the vicinity of the bottom wall surface 11 in the flow path 17 by the action of the viscosity of the flow of the cross flow F1. Distributed. Since the fine particles try to diffuse in the solvent, there is a balance between the Brownian motion of the fine particles, that is, the diffusion and the force caused by the cross flow F1, and the concentration of the fine particles from the bottom wall surface 11
exp (-| U | / D)
However, | U |: Cross flow velocity, D: Exponential (attenuation) function distribution represented by diffusion coefficient.

  On the other hand, the axial flow F2 from the inlet port 15 toward the outlet port 16 becomes a laminar flow called Poiseuille flow. As shown in FIG. 8, the center is the maximum flow velocity, and the paraboloid of zero flow velocity at the bottom wall surface 11 and the upper wall surface 12 is obtained. It has a surface-shaped flow velocity distribution. Therefore, the flow velocity of the axial flow F2 increases as the distance from the wall surfaces 11 and 12 increases, and the combination of the flow velocity distribution of the axial flow F2 and the fine particle distribution by the cross flow F1 described above finally depends on the diffusion coefficient of the fine particles. The moving speed toward the outlet port 16 is different, and the fine particles are separated in accordance with the difference in diffusion coefficient (usually the difference in particle size) in the length direction of the separation channel 10 (that is, the flow direction of the axial flow F2). It will be. This is the principle of fine particle separation by the crossflow FFF.

  However, in the structure of the separation channel 10 as described above, it is difficult to make the cross flow velocity uniform by making the permeability of the upper wall surface 12 and the bottom wall surface 11 uniform. Further, since it is necessary to form two different carrier solvent flows F1 and F2 that are orthogonal to each other, the structure is complicated, the apparatus becomes large, and two pumps for feeding the solvent are required. .

  On the other hand, an FFF having an asymmetric channel structure has been proposed, and the practical application of the FFF has progressed. FIG. 9 is a longitudinal sectional view of the asymmetric separation channel 20. In this separation channel 20, no opening is provided in the upper wall surface 12, and as the carrier solvent supplied from the inlet port 15 flows as the axial flow F <b> 2, the semipermeable membrane 11 b is gradually permeated to open the opening of the support wall 11 a. After that, it flows out downward, and this becomes a cross flow F1 substantially orthogonal to the axial flow F2. According to this configuration, there is an advantage that the structure of the separation channel 20 is simple and only one pump is required to supply the carrier solvent.

  However, in the case of the asymmetric separation channel 20 as described above, since the cross flow F1 is also covered by the carrier solvent supplied from the inlet port 15, the flow rate per unit cross-sectional area of the axial flow F2 becomes closer to the outlet port 16. Decrease and flow velocity decreases (decreases in a linear function). Therefore, there is a problem that the retention time, which is the time until the fine particles reach the outlet port 16, becomes extremely slow. As a result, not only does the separation take time, but particularly fine particles having a small diffusion coefficient may stay in the vicinity of the outlet port 16 and may not flow out of the outlet port 16.

  In order to solve this problem, a separation channel having a structure as described in Non-Patent Document 1 has been proposed. FIG. 10 is a perspective view of the separation channel 30. The separation channel 30 is formed in a trapezoidal shape when viewed from above so that the channel width W narrows in a linear function from the inlet port 15 toward the outlet port 16. That is, the space between the side wall surfaces 13 and 14 is gradually narrowed in the flow direction of the axial flow F2. For this reason, the flow velocity of the axial flow F2 increases as the cross-sectional area decreases toward the outlet port 16, and thus the above-described problem of a decrease in flow velocity due to a decrease in the flow rate of the carrier solvent is reduced. However, since the channel width in the vicinity of the outlet port 16 is narrowed, the band concentration of the sample (fine particles) in the vicinity of the outlet port 16 is several times higher, and the resolution is degraded due to the high concentration (high density of the fine particles). Realize. Further, in a portion where the channel width is narrow, a side effect due to the interaction between the side wall surfaces 13 and 14 and the fine particles in the solvent becomes a problem, which also causes a reduction in resolution.

  In general, when the flow velocity of the cross flow F1 is constant, the resolution is improved in inverse proportion to the square of the channel height H, and the resolution is increased with a specific diffusion coefficient as the center. However, it is difficult to sufficiently increase the resolution of fine particles having a diffusion coefficient far from this specific diffusion coefficient. Therefore, a method for improving the resolution by controlling the supply flow rate of the carrier solvent so as to change the flow velocity of the cross flow F1 with time has also been proposed. In this method, the cross flow F1 is appropriately changed according to the passage of time by combining the change of the flow rate of the supply solvent near the inlet port 15, the change of the flow rate of the cross flow F1, and the back pressure control of the axial flow F2. However, it is difficult to keep the flow rate of the carrier solvent flowing out from the outlet port 16 constant, and fluctuations in the flow rate give an error to the detector for detecting the fine particles, causing a problem in detection accuracy. Therefore, there is a demand for a separation channel having such a structure that high resolution can be obtained without performing program control of a complex flow rate over a particle size as wide as possible.

U.S. Pat. No. 4,147,621 US Pat. No. 5,193,688 A. Litzen, KG Wahlund, "Zone Broadening and Dilution in Rectangular and Trappoidal Asymmetric Flow Field-Flow Fractionation Channels ( Zone Broadening and Dilution in Rectangular and Trapezoidal Asymmetrical Flow Field-Flow Fractionation Channels), Analytical Chemistry, American Chemical Society, 1991, 63, p.1001-1007

  The present invention has been made to solve the above-mentioned problems, and its main purpose is to suppress an increase in the band concentration of fine particles near the outlet port while suppressing a decrease in the flow velocity of the axial flow. It is an object of the present invention to provide a field flow fractionation device that can prevent degradation in resolution caused by the above. Another object of the present invention is to provide a field flow fractionation apparatus that can achieve high resolution for fine particles having a wider range of diffusion coefficients.

  In the separation channel in the conventional field flow fractionation apparatus, although the channel width is changed along the flow direction of the axial flow, the channel height is assumed to be constant. On the other hand, in the field flow fractionation device according to the present invention, the channel height is changed along the flow direction of the axial flow to change the cross-sectional area of the separation channel, and thereby the flow velocity of the axial flow is changed. I try to adjust it.

That is, the present invention made to solve the above problems has a bottom wall surface through which carrier fluid can permeate and through which fine particles to be separated do not permeate, an upper wall surface facing the bottom wall surface, and a pair of side wall surfaces. A separation channel provided with an inlet port and an outlet port, and a feeding means for introducing a carrier fluid into the inlet port of the separation channel, the carrier heading from the inlet port to the outlet port inside the separation channel In the field flow fractionation device that separates the fine particles in the flow direction of the carrier fluid inside the separation channel while causing a part of the fluid to flow out through the bottom wall surface to the outside as the fluid flows,
The distance between the bottom wall surface and the top wall surface of the separation channel is narrowed along the flow direction in at least a part of the flow direction of the carrier fluid.

  The separation channel does not necessarily have to be installed substantially horizontally such that the bottom wall surface is on the lower side and the upper wall surface is on the upper side, and the installation form is not particularly limited, such as upside down or standing upright. Therefore, the bottom wall surface, the upper wall surface, and the side wall surface referred to here are names for convenience when it is considered that the cross flow goes downward, and do not indicate the positional relationship in the actual installation state.

  In the field flow fractionation device according to the present invention, since the distance between the bottom wall surface and the top wall surface of the separation channel in the direction along the axial flow, that is, the channel height is reduced, the channel height is constant. Compared with the case where it is, the flow velocity of an axial flow can be increased in the exit port side. As a result, a sufficient flow rate can be obtained even if the channel width is increased to some extent on the outlet port side, so that an increase in the fine particle band concentration in the vicinity of the outlet port is suppressed, and peripheral effects are also suppressed and resolution is improved. Can be increased. At the same time, by maintaining the flow velocity of the axial flow, the retention time can be prevented from becoming extremely long, and fine particles having a small diffusion coefficient can be reliably discharged from the separation channel for detection.

  In the field flow fractionation apparatus according to the present invention, various modes of reducing the channel height can be considered. That is, conventionally, the flat bottom wall surface and the top wall surface of the separation channel are arranged so as to be parallel to each other. For example, either the bottom wall surface or the upper wall surface approaches the other along the axial flow. By providing such an inclination, the channel height can be monotonously decreased in a linear function along the flow direction of the axial flow. In addition, by making either the bottom wall surface or the upper wall surface a curved surface according to a loose quadratic function, the channel height is monotonically decreased in a quadratic function along the flow direction of the axial flow. It can also be. In addition, the flow direction of the axial flow of the channel height is achieved by forming either the bottom wall surface or the upper wall surface into a shape in which two flat surfaces having different inclinations are connected smoothly (that is, having an appropriate curvature). The degree of decrease along the line may change near a certain position.

  Furthermore, the channel height as described above is monotonically reduced in a linear function, a quadratic function, a polygonal line, or the like only in a part of the range, not over the entire axial flow of the separation channel. A portion may be provided. In particular, if the channel height becomes extremely small near the outlet port, the axial flow may deviate from the ideal Poiseuille flow and hinder the separation of fine particles. It is preferable that the first half is monotonously decreased along the flow direction and the second half is constant along the flow direction.

  On the other hand, the distance between the pair of side walls of the separation channel, that is, the channel width may be constant in the entire range of the flow direction of the axial flow, or the axial direction as in a trapezoidal configuration as viewed from above. It is good also as monotonously decreasing along a flow direction in the whole range of the flow direction of a flow. In the former case, the channel height needs to be considerably reduced in order to increase the flow velocity of the axial flow near the outlet port, but in the latter case, the channel width is also somewhat reduced, so the degree of decrease in the channel height is reduced. This makes it possible to form a more ideal Poiseuille flow.

  According to the field flow fractionation device of the present invention, the band concentration of the fine particles in the vicinity of the outlet port can be avoided even in the outlet port while avoiding an extremely long retention time by obtaining a sufficient flow velocity of the carrier fluid. By suppressing the increase, the spread of the band can be reduced and the peripheral effect can be suppressed to increase the resolution. In addition, not only the channel height but also the channel width can be narrowed at the same time, so that a relatively wide channel width can be secured by suppressing the narrowing of the channel width. Separation with high resolution is possible for fine particles.

  Hereinafter, several embodiments of the FFF device according to the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected about the component demonstrated with the conventional structure already demonstrated in drawing of each of these Examples, and the correspondence is clarified.

  First, an FFF device according to a first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic perspective view of the separation channel 40 in the FFF of the first embodiment, and FIG. 2 is a longitudinal sectional view of a part of the separation channel 40.

  In the separation channel 40 according to the first embodiment, the channel width W is constant as in the conventional example shown in FIG. 7, but the channel height H is monotonically linearly along the flow direction of the axial flow F2. It is configured to decrease. That is, with the upper wall surface 12 as a reference, the bottom wall surface 11 has a structure inclined obliquely upward along the flow direction of the axial flow F2.

  FIG. 3 shows a configuration example of the FFF device. First, a sample in which fine particles to be separated are dispersed is introduced into the flow channel 17 of the separation channel 40 from a sample introduction port 3 provided separately from the inlet port 15 (see FIG. 3A). Immediately after the fine particles are introduced into the flow path 17, the sample width is wide. Therefore, by flowing the solvent countercurrently from both the inlet port 15 and the outlet port 16, diffusion of the fine particles is suppressed and the sample width is narrowed (that is, concentrated). To go through the process. Thereafter, the carrier solvent (carrier fluid in the present invention) is supplied from the pump 1 to the inlet port 15 at a predetermined flow rate. Then, while the carrier solvent passes through the flow path 17 of the separation channel 40, the fine particles are separated according to the diffusion coefficient, that is, according to the particle diameter, and flow out from the outlet port 16 (see FIG. 3B). Fine particles in the flowing solvent are sequentially detected by a detector 2 such as a multi-angle scatterometer.

  In the separation channel 40, the channel height H is narrowed as the carrier solvent progresses in the flow path 17, so that the cross-sectional area of the flow path 17 becomes narrow. Therefore, the separation channel 40 is compared with the conventional structure shown in FIG. Thus, the flow rate of the carrier solvent near the outlet port 16 can be increased. As a result, the increase in the band concentration of the fine particles in the vicinity of the outlet port 16 is suppressed, and the band broadening and the peripheral effect due to the concentration are achieved. Further, since the channel width W in the vicinity of the outlet port 16 is wide, separation with high resolution can be performed on fine particles having a wide range of diffusion coefficients. In FIG. 3, the sample introduction port 3 for introducing fine particles is provided separately from the inlet port 15, but the illustration of the sample introduction port 3 is omitted in other drawings for convenience of explanation.

  Next, an FFF device according to a second embodiment of the present invention will be described with reference to FIG. FIG. 4 is a schematic perspective view of the separation channel 50 in the FFF of the second embodiment. In the separation channel 50 according to the second embodiment, not only the channel height H decreases monotonically in a linear function along the flow direction of the axial flow F2, but also the conventional example shown in FIG. Similarly, the channel width W also decreases monotonically in a linear function along the flow direction of the axial flow F2. However, since the channel height H is decreased, the degree of decrease in the channel width W is suppressed, and the channel width W near the outlet port 16 is widened. On the contrary, since the channel width W is decreased, the degree of decrease in the channel height H can be suppressed as compared with the configuration of the first embodiment.

  That is, by reducing both the channel width W and the channel height H along the flow direction of the axial flow F2, the degree of reduction in the cross-sectional area itself of the flow path 17 is ensured while suppressing each extreme decrease. Yes. Therefore, since the channel height H is not extremely reduced even near the exit port 16, the Poiseuille flow is less likely to be disturbed, and the channel width W is not extremely reduced, so that an increase in bandwidth density and peripheral effects are suppressed to increase resolution. be able to. In addition, by securing the channel width W to a certain extent, separation with high resolution can be performed on fine particles having a wide range of diffusion coefficients.

  In the FFF devices according to the first and second embodiments, the channel height H is monotonically decreased in a linear function along the flow direction of the axial flow F2. However, the channel height H needs to be linear. For example, it may be a quadratic function. In such a case, one or both of the bottom wall surface 11 and the top wall surface 12 is not a flat surface but a curved surface.

  Further, the channel height H does not have to be monotonously decreased along the flow direction of the axial flow F2, and further does not have to be monotonically decreased along the flow direction of the axial flow F2. FIG. 5 is a schematic perspective view of the separation channel 60 in the FFF of the third embodiment, and FIG. 6 is a longitudinal sectional view of a part of the separation channel 60. In the separation channel 60 of the third embodiment, the channel width W is monotonically decreased in a linear function along the flow direction of the axial flow F2 as in the second embodiment. On the other hand, the channel height H is reduced to a halfway (specifically, up to the position indicated by P in FIGS. 5 and 6) in a linear function, but is further forward (side closer to the outlet port 16). It is assumed to be constant.

  Specifically, as shown in FIG. 6, the upper wall surface 12 is a substantially horizontal plane, but the bottom wall surface 11 is an inclined plane closer to the inlet port 15 than the position indicated by P, the position indicated by P. The side closer to the outlet port 16 than the vicinity is a substantially horizontal plane, and both the planes are connected by a gentle curved surface near the position indicated by P. With such a configuration, an extremely narrow channel height H in the vicinity of the outlet port 16 can be suppressed, and the Poiseuille flow can be maintained in a good state, and fine particles can be appropriately separated.

  In each of the above embodiments, the bottom wall surface 11 is inclined or its shape is changed in order to reduce the channel height H, but the upper wall surface 12 may be similarly deformed. Moreover, in the said Example, although the separation channels 40, 50, and 60 are mounted substantially horizontally, as above-mentioned, the separation channel can take the installation aspect freely, such as upside down and standing arrangement.

  Furthermore, since each of the above-described embodiments is merely an example of the present invention, it is included in the present invention even if corrections, changes, additions, etc. are made as appropriate within the scope of the present invention in points other than those described above. Obviously.

The perspective view of the separation channel by one Example (1st Example) of this invention. The longitudinal cross-sectional view of a part of the separation channel of the first embodiment. The schematic block diagram of FFF of 1st Example. The perspective view of the separation channel by other Example (2nd Example) of this invention. The perspective view of the separation channel by the other Example (3rd Example) of this invention. The longitudinal cross-sectional view of a part of the separation channel of the third embodiment. The perspective view which shows an example of the basic structure of the separation channel of crossflow system FFF. FIG. 8 is a longitudinal sectional view of a part of the separation channel shown in FIG. 7. FIG. 6 is a longitudinal sectional view of a part of a separation channel according to another conventional configuration. The perspective view of the separation channel by other conventional structures.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Pump 2 ... Detector 3 ... Sample introduction port 40, 50, 60 ... Separation channel 11 ... Bottom wall surface 11a ... Support wall 11b ... Semipermeable membrane 12 ... Upper wall surface 13, 14 ... Side wall surface 15 ... Inlet port 16 ... Outlet Port 17 ... Flow path F1 ... Cross flow F2 ... Axial flow

Claims (5)

A separation channel having a bottom wall surface through which carrier fluid can permeate and through which fine particles to be separated do not permeate, an upper wall surface facing the bottom wall surface, and a pair of side wall surfaces, and an inlet port and an outlet port provided at both ends; A feeding means for introducing a carrier fluid into the inlet port of the separation channel, and a part of the fluid as a cross flow as the carrier fluid flows from the inlet port to the outlet port inside the separation channel. In the field flow fractionation device that separates the fine particles in the flow direction of the carrier fluid inside the separation channel while flowing out through the bottom wall surface,
A field flow fractionation device, wherein a distance between a bottom wall surface and an upper wall surface of the separation channel is narrowed along a flow direction in at least a partial range of the flow direction of the carrier fluid.   The distance between the bottom wall surface and the top wall surface of the separation channel is monotonously decreased along the flow direction in the entire range of the flow direction of the carrier fluid. Field flow fractionation device as described.   The space between the bottom wall surface and the top wall surface of the separation channel is monotonously decreased along the flow direction in the first half of the flow direction of the carrier fluid, and is constant in the second half. 2. The field flow fractionation device according to 1.   The field flow fractionation according to any one of claims 1 to 3, wherein a distance between the pair of side wall surfaces of the separation channel is constant over the entire range of the flow direction of the carrier fluid. apparatus. The field flow according to any one of claims 1 to 3, wherein an interval between the pair of side wall surfaces of the separation channel is monotonously decreased along a flow direction of the carrier fluid. Fractionation device.

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