High Pressure Gradient Chamber For Liquid Chromatography

Abstract

An element having a chamber therein is secured to a device which is provided with inlet and outlet passages communicating with the chamber. A stirrer is positioned in the chamber and serves to mix liquid within the chamber with a fluid introduced to the chamber under high pressure via the inlet passage, the resultant mix being forced out of the chamber through the outlet passage.

Description

BACKGROUND AND SUMMARY OF THE INVENTION

Gradient elution is a useful technique in many applications of chromatography and is particularly applicable to high pressure liquid chromatography where high resolution and speed of analysis are obtainable. However, available gradient devices are complex and expensive. For example, one such device requires a substantial number of high pressure valves, a holding coil and a gradient chamber, whereas another known arrangement utilizes a plurality of pumps to develop the gradient.

The present invention is concerned with a simple, efficient gradient device which can be produced at a fraction of the cost of known devices and which permits accurate mixing for a precise gradient without introducing voids which would interfere with subsequent detection in the chromatographic column. This is accomplished by combining an element having a chamber therein and a cap device. The cap is provided with a suitable passage to direct a solvent under high pressure into the chamber to be mixed by a magnetic stirrer with an eluant within the chamber, the pressure forcing the mix from the chamber through a second passage in the cap to the liquid column where the analysis is made.

The invention now will be described in greater detail with reference to the accompanying drawings which illustrate a preferred embodiment of the invention and wherein:

FIG. 1 is a top plan view of a high pressure gradient chamber according to the invention;

FIG. 2 is a view partially in section taken along line 2--2 of FIG. 1; and

FIG. 3 is a view in section taken along lines 3--3 of FIG. 2.

Referring to the drawings, the basic components of the device are a cap 10, element 12, retainer 14, stem 16, and magnetic stirring bar 18. The structural details of these elements can most clearly be seen in FIGS. 2 and 3.

Cap 10 is a generally cylindrical element. A cylindrical recess 20 is provided at one end of the cap, this recess being threaded along a portion of its length as indicated at 22. A pair of passages are machined in the cap, these passages communicating with the recess 20. One of these passages is designated as an inlet passage 24, while the other passage 26 serves as an outlet. The ends of passages 24 and 26 remote from the recess 20 communicate with internally threaded cavities 28 and 30 which receive conventional fittings 32 and 34, respectively. Fitting 32 is associated with a conduit 36 which is joined to a source of solvent moved under high pressure by a pump (not shown), while fitting 34 couples the outlet passage 26 to a liquid chromatographic column (not shown) via conduit 38.

Element 12 is generally cylindrical and has an annular flange portion 40 at one end thereof. The external diameter of the flange is slightly less than the diameter of the recess 20 in cap 10. Consequently, element 12 is received within recess 20 as shown. In order to hold the element within recess 20, retainer 14 is employed. This retainer is an annularly shaped device having external threads which cooperate with threads 22 within recess 20. The diameter of the passage through retainer 14 substantially corresponds to the diameter of the cylindrical portion of element 12. Consequently, retainer 14 is slipped over the end of element 12 and is screwed into recess 20 so as to engage the shoulders of the element which are defined by flange 40. Thus, element 12 is held in position within the recess 20 of cap 10. The retainer 14 is provided with recesses 42 in one face thereof, these recesses serving to accept a suitable tool for tightening the threaded retainer, and thus the element 12 within recess 20.

Element 12 is provided with a central cavity which defines a mixing chamber 44 and which is co-axial with the cylindrical portion of the element extending a greater part of the length thereof. The chamber 44 is of sufficient diameter to communicate with the inlet and outlet passages 24 and 26. Magnetic stirring bar 18 rests at the bottom of chamber 44, the bar being a conventional stirring bar as can be seen more clearly by reference to FIG. 3.

Also located within chamber 44 is stem 16. This stem is generally cylindrical in shape and is threaded at one end to be received within a threaded cavity 46 formed at the end of passage 24 in cap 10. A passage 48 extends the length of stem 16 and completes a path from inlet passage 24 through the stem to the interior of chamber 44.

In order to prevent leakage from the mixing chamber, the upper surface of flange 40 is provided with an annular groove within which an O-ring 50 is positioned. This O-ring prevents the passage of fluid between the mating surfaces of recess 20 and flange 40 when the retainer 14 positions the element 12 within the recess.

To mount the unit to a suitable support, shown as 52 in FIG. 2, the cap 10 is provided with a plurality of holes 54 through which suitable bolts 56 project, the entire assembly being held to support 52 by nuts 58 secured to the bolts.

The cap, mixing chamber, stem and retainer are preferably made of stainless steel and O-ring 50 is a material such as polysulfide which exhibits high solvent resistance.

In operation, the mixing chamber 44 is filled with a starting eluant and a solvent of high elution power is pumped at high pressure via conduit 36, inlet passage 24, and passage 48 into the chamber. Mixing is accomplished by the actuation of stirring bar 18 by means of a magnetic field external to the assembly, the stainless steel being non-magnetic and therefore not interfering with the operation of stirrer 18. The high pressure mixture is forced out of the chamber 44 through passage 26 and conduit 38 to the chromatographic column.

The actual size of the chamber is determined by the shape of the gradient desired. The larger the chamber, the less steep is the gradient developed.

While the device described is particularly adapted to a liquid chromatography, it also can be used for slurry packing small packing materials into columns. In such an arrangement, the packing material is added to a carrier solvent in the desired slurry consistency and is poured into the mixing chamber. The slurry is then pumped from the mixing chamber to the column.

Claims

What is claimed is:

1. A device for developing a high pressure gradient for liquid chromatography comprising:

a cap;

an element having a chamber therein;

means for securing the element to said cap;

inlet and outlet passages in said cap, said passages communicating with the chamber; and

stirring means within said chamber for mixing fluid within the chamber with fluid introduced under pressure to the chamber through the inlet.

2. A device as set forth in claim 1, wherein said stirring means is magnetically operable.

3. A device as set forth in claim 1, wherein said cap includes a recess within which said element is secured.

4. A device as set forth in claim 3, wherein said securing means comprises a retainer operatively related to the recess and the element to hold said element within the recess.

5. A device as set forth in claim 3, further comprising sealing means within said recess engaging the element and the cap to prevent escape of fluid from the chamber except through the outlet passage.

6. A device as set forth in claim 1, wherein said element is provided with a cylindrical cavity to define the chamber, the device further comprising a stem secured to said cap and projecting within the cavity, said stem having a passage therethrough communicating with the inlet passage to introduce the fluid under pressure to the interior of the chamber.

7. A device as set forth in claim 6, wherein said stirring means is located between the stem and the bottom of said cavity and is magnetically operable.

8. A device as set forth in claim 1, further comprising sealing means engaging the element and the cap to prevent escape of fluid from the chamber except through the outlet passage.