US 3595531 A
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United States Patent l l l I 3,595,533 I  lnvc mors Alan J. Williams;  References Cited Charles .I. Starnes, both of Midland, Mich. UNITED STATES PATENTS "P 8733 2,518,758 8/1950 Cook 259 010. 46 2,999,673 9/l96l Kessler 259/010. 46 Paemd My 3 520 51s 7/1970 Knedlik 259/7  Assignee The Dow Chemical Company Midland, Mich. Primary ExaminerWilliam 1. Price Assistant Examiner-Philip R. Coe Attorneys-Griswold & Burdick and Earl D. Ayers ABSTRACT: This invention relates to apparatus for use in indicatin the presence of substances in a small stream of liquid,  APPAMTus and pa rticularly to mixing apparatus for use in connection 6 clmms 2 Drawmg with chromatographic apparatus utilizing microcolumns.  US. Cl 259/7, The apparatus is a spherical chamber having a close-fitting 259/DlG. 46 ball therein, a pair of inputs and an output. The ball is non- [5l] Int. Cl B01! 7/02, reactive with the materials to be mixed and has a magnet em- BOlf 13/08 bedded therein. The sphere is in two parts to permit easy  Field of Search 259/DIG. cleaning and/or replacement of the ball. External magnetic 46, 7, 5, 8;'4l6/3 means cause rotation of the ball.
MIXER APPARATUS BACKGROUND OF THE INVENTION This invention relates to apparatus for use in indicating the presence of substances in a small stream of liquid, and particularly to mixing apparatus for use in connection with liquid chromatographic apparatus utilizing microcolumns.
in many automated organic analysis systems the effluent stream from a chromatographic column is mixed with an excess of indicator salt solution delivered at a constant rate. When so-called microcolumns are used in the chromatographic apparatus, special problems occur in mixing the salt (or other) solution with the effluent stream.
For example, the amount of column effluent representing any one substance is very small and often is not widely separated from that part of the effluent representing other materials.
Thus, difficulty has been encountered when mixing the effluent and indicator in that the volume of material either results in a great amount of indicator for a small amount of effluent or the inventory in the mixer results in the effiuent representing more than one 'material being present in the mixer.
.Accordingly, a principal object of this invention is to provide improved apparatus for mixing small volumes of materials.
Another object of the invention is to provide improved, low inventory volume mixing apparatus.
A further object of this invention is to provide improved, easy to assemble apparatus for mixing small volumes of material.
in accordance with this invention there is provided a two part housing having a spherical inner chamber.
A sphere having magnetic means disposed therein fits closely but slidably in the chamber. A pair of input means and an output means spaced from the input means communicate with the chamber.
The chamber and the sphere are nonreactive with the materials to be mixed. The sphere is rotated by means of an externally disposed rotating magnetic field.
Because of the close spacing between the sphere and the chamber walls, only a few microliters of liquid inventory occurs and excellent mixing is accomplished.
The invention, as well as additional objects and advantages thereof, may best be understood when the following detailed description is read in connection with the accompanying drawing, in which:
FIG. lis a diagrammatical view of chromatographic apparatus incorporating this invention, and
FIG. 2 is a side elevational view, partly broken away and in section, of mixing apparatus in accordance with this invention.
Referring to the drawing, and particularly to FIG. I, there is shown chromatographic apparatus including a chromatographic column 10, a reservoir or source of material to beanalyzed 12, and a feed tube 14 and pump 16 coupledbetween the reservoir 12 and the top of the column 10.
A tube 18 is coupled between the output or bottom of the column and a mixer, indicated generally by the numeral 30. A source of indicator material 20 is coupled through a constant volume pump 24 and tube 22 to the mixer 30.
The output of the mixer 30 is coupled through the tube 32 to a detector 34. A line 36 goes to waste or liquid utilization means from the output of the detector.
The output of the detector, an electrical signal, is coupled are se arated. The mating groun to provide a liqui tight seal and the parts 38, 40 are sealed together usually by a shrink-fitted adhesive strip 42.
The sphere 44, made of polytetrafluorethylene, for example, has magnetic means 46, such as a bar magnet, disposed within it.
A motor 48, mounted on a base 50 adjacent to the mixer 30, has a'magnet 52 fixedly coupled to the rotatable shaft of the motor. i
In operation, with the effiuent of the column 10 being fed directly to the mixer 30 along with indicator liquid from the reservoir 20, the rotation of the magnet 52 by meanspf the motor 12 causes a rotating magnetic field which induces rotation of the sphere 44 in the chamber 54.
The liquid is subjected to a shearing action caused by the rotation of the sphere 44, causing excellent mixing of the effluent and the indicator liquid, yet the liquid inventory in the mixer is only of the order of a few microliters.
The detector used with one apparatus in accordance with this invention may be a Gilford Monitor or other suitable spectrophotometer, for example.
It has also been 'foundthat mixing devices made in accordance with this invention either greatly reduce or eliminate the pulsations due to the pumping systems, thus offering more constant flow.
Because the mixer may be closely coupled to the output of the chromatographic column and to the detector, and because of the small inventoryin the mixer, (see FIG. 2), sharper, better defined output of the instrument may be obtained.
What I claim is:
1. Apparatus for mixing very small volumes of fluids, comprising a two part body which, when the parts are joined in operative relationship, has a spherical chamber therein, a spherical element having magnetic means incorporated therein, said element having a diameter such that it fits closely but loosely slidably within said spherical chamber, said eleme'nt being made of a material which is nonreactive with materials to be mixed in said apparatus, means for introducing materials to be mixed to said chamber, means remote from said means for introducing materials for withdrawing mixed materials from said chamber, means for joining said body parts together in a fluidtight manner, and means for imposing a moving magnetic field on said spherical element to induce rotation thereof.
2. Apparatus in accordance with claim 1, wherein said body is made of a vitreous material.
3. Apparatus in accordance with claim 1, wherein said body parts having mating ends with a hemispherially shaped surface extending inwardly therefrom, said parts being joined at said mating ends.
4. Apparatus in accordance with claim 1, wherein said means for imposing a moving magnetic field comprises a rotatable magnet disposed adjacent to said body part.
5. Apparatus in accordance with claim 1, wherein said magnetic means in said spherical element is a bar magnet.
6. Apparatus in accordance with claim 1, wherein said means for joining said body parts together comprises a fluid impervious tightly adhering tapelike element.
edges of the two parts 38, 40 are