JPH0641946B2 - Fluid conduit for use in chromatographic equipment - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a fluid conduit for use in a chromatography device, in particular a fluid conduit having a two-dimensionally bent through opening.

PRIOR ART It is known that in straight conduits the fluid has the flow characteristic of forming a parabolic velocity profile front. This occurs as a result of the peripheral fluid being slowed down along the interface with the inner surface of the conduit. This slowing action of the flow shifts towards the central section of the fluid, decreasing with distance. Therefore, any cylindrical band of fluid entering the conduit with a flat front will be stretched due to this phenomenon. In chromatography, this is generally a band dispersion (b
and dispersion).

Until recently, chromatographic researchers were rather enthusiastic about the band dispersion occurring within the separation column and were less concerned with band dispersion within the connecting conduit outside the column. However, recent advances in column technology have led to more interest in the effects of extra-column dispersion and its reduction. Extra-column dispersion may cause unacceptable bands, and thus peaks, that extend both before and after the separation column.

In the conduit in front of the column, the band dispersion disturbs the flat front surface of the sample mixture, thus causing the sample mixture to be injected into the column in a non-uniform concentration. The band dispersion in the conduit behind the column between the column and the detector tends to spread out each separated component, and such expansion causes an overlap of the separated components. This overlap results in a remixing of the preseparated sample components for all intents and purposes. Therefore, in modern low dispersion chromatography equipment, band dispersion of the connecting conduit outside the column is an important consideration.

In general, one attempt to reduce dispersion in fluid conduits is to fabricate conduits that are short and have a small inner diameter. However, such conduits are quite vulnerable to blockages, which further greatly complicates chromatographic equipment assembly and operation.

Problem to be Solved by the Invention It was therefore an object of the present invention to provide a fluid conduit which can be used for chromatographic devices, which exhibits the lowest band dispersion.

[Means for Solving the Problem] According to the present invention, the above-mentioned problem is constituted by a pipe in which a fluid conduit forms a two-dimensionally bent through hole, and the through hole has a substantially uniform cross section. And a hollow tubular sleeve in which the tube is fixedly connected to the sleeve at both ends by discs.

According to an advantageous embodiment of the invention, the cross section is circular.

According to another advantageous embodiment of the invention, the tube is made of stainless steel.

EXAMPLES Next, the present invention will be described in detail with reference to the illustrated examples.

A liquid conduit, shown generally at 10 in FIGS. 1 and 2 (but not to scale), is a liquid conduit according to one embodiment of the present invention having a tube 12 having a continuous through opening 14. The tube 12 is formed so that the through hole is two-dimensionally bent. As used herein, the term "bend" should be understood to mean a continuous turn path having periodic peaks and valleys of substantially equal amplitude. As a result of the tortuosity, the radial velocity of the fluid passing through the tortuosity continuously changes in magnitude and at the same time periodically changes direction. In the illustrated embodiment, the tube 12 is secured within a conduit 16 generally designed to allow the tube 12 to be conveniently introduced into the fluid path of conventional equipment.

In the preferred embodiment, the tube 12 is stainless steel and has an outer diameter of about 0.25 mm (about 0.02 inch) and an inner diameter of about 0.25 mm.
(About 0.01 inch).

The tube 12 with a length of about 42.5 cm is formed into a bent body,
The bent body has a longitudinal distance between adjacent peaks of about 1.8.
mm and a lateral distance between adjacent peaks of about 0.5 mm. Such a turn is about 38 cm long. The bent body can be formed by a technique known to those skilled in the art.
It can be formed, for example, by inserting the tube 12 between complementary shaped gear pairs in the same way as when loading the cloth into the wringer. The meandering through-holes 14 should be formed so that a uniform cross section is maintained over the entire length of the tube 12. In this way, the possibility of blockage of the through-hole 14 is virtually completely eliminated in most fluid chromatography applications.

In order to use said tube 12 in a conventional liquid chromatographic apparatus, tube 12 has a conduit 16 of conventional dimensions, namely a conduit 16 having an inner diameter of about 1.3 mm and an outer diameter of about 1.6 mm.
Fixed inside. Although any means can be applied for this fixing, it is advantageous to attach the disc 18 with the central through hole 20 to the tube 12. In one embodiment, each has a thickness of about 1 mm and the inner diameter of the center through hole 20 is about 0.
A pair of discs 18 having a diameter of 5 mm and an outer diameter of about 1.6 mm was used. The discs 18 were attached to each end of the tube 12 by known techniques, such as soldering. Thereafter, the disk 18 was similarly fixed to the end 22 of the conduit 16 by soldering.

As far as substantiated, the liquid conduit 10 formed according to the preferred embodiment described above exhibits negligible band dispersion. It is believed that the reason for this is that the flowing liquid is unable to induce a parabolic surface flow at any point along the bend. Parabolic flow is prevented. This is because the continuous bending of the through-hole 14 causes the radial velocity to change continuously and to change direction. Furthermore, above the minimum flow rate below 1 ml / min, the flow at all points in the bend is the same as a continuous radial flow with little or no influence by laminar flow.

In the following description with respect to Figures 3A and 3B showing a comparative study between a conduit according to the invention and two different conventional fluid connection tubes, the variance of the peak (δ ² ) was used as a comparison criterion.

This factor is because the ideal chromatographic peak is a Gaussian curve or bell shape, and from a practical and mathematical point of view, this is not the standard deviation (δ), but its square (δ ² ), that is, the normal distribution standard scale. It was chosen because of some dispersion. In addition, the variance (δ ² ) was normalized with respect to length to make a clearer comparison.
Therefore, the ordinate axis, per centimeter microliter square units for chromatographic purposes per unit length distributed with ^{(μl 2 / cm) (δ} 2/1)
I took it. Another comparison variable is the flow rate plotted on the abscissa, which is the unit of milliliters per minute (m
l / min).

Referring particularly to FIG. 3A, the linear plot 2
4 is the standardized peak dispersion for flow rate for a straight tube having an inner diameter of about 0.18 mm (about 0.0017 inch). Plot 26 is a graph for a conduit designed in accordance with the principles of the present invention and having an inner diameter of about 0.25 mm (0.01 inch).

Referring to FIG. 3B, graph 26 is graph 28.
4 shows a comparison with a coiled tube having a tube inner diameter of about 0.13 mm and a coil diameter of about 1 mm.

From the comparison below, it is clear that the liquid conduit 10 is significantly better than a straight tube. The straight tube dispersion increases clearly linearly with the flow rate over the flow rate range tested. This linear increase can be regarded as manifesting undesired extra-column effects or dispersion even when the inner diameter of the conduit is smaller than that used in the liquid conduit 10 according to the principles of the present invention. Moreover, while the dispersion of conduit 10 described herein is close to the coiled tube at high flow rates, the coiled tube has significantly higher dispersion at flow rates of about 1 ml / min. From a rigorous analysis of the results of the experiments carried out so far, a dispersion of about 0.04 μl ² / cm is easily achieved according to an embodiment of the method according to the invention. Accordingly, the fluid conduit according to the present invention provides an embodiment not previously possible.

Therefore, the liquid conduit 10 as described herein can be used as a connecting tube with low dispersion in a liquid chromatography device. That is, such a conduit has applicability, for example, as a connecting pipe between an injection valve and a separation column or between a column and a detector cell. In addition, such a conduit can advantageously also be used as a mixing device due to the inherent radial flow characteristics inside.

Although the method according to the invention has been described in a special embodiment,
It will be apparent to those skilled in the art that other arrangements and applications are possible. Therefore, the description provided herein is merely illustrative and the invention should be considered as limited by the following claims and their reasonable interpretation.

[Brief description of drawings]

1 is a cross-sectional view of one embodiment of a conduit for carrying out the method according to the invention, FIG. 2 is an exploded view of a portion of the conduit shown in FIG. 1, and FIGS. 3A and 3B are shown in FIG. FIG. 4 shows a comparative graph showing the reduction in dispersion of the indicated conduit. 10 ... Liquid conduit, 12 ... Pipe, 14 ... Through port, 18 ... Disc, 20 ... Opening, 22 ... End

Claims (3)

[Claims] 1. A fluid conduit comprising a tube forming a two-dimensionally bent through opening, the through opening having a substantially uniform cross section and a hollow tubular sleeve, the sleeve comprising: Fluid conduit for use in a chromatographic device, characterized in that the tube is fixedly connected at both ends to the sleeve by discs. 2. A fluid conduit for use in a chromatography device according to claim 1 wherein the cross section is circular. 3. A fluid conduit for use in a chromatography device according to claim 1 wherein said tube is made of stainless steel.