A sample injection valve for use in high-pressure liquid chromatography

182 14.

15. 16. 17. 18. 19. 20. 21. 22.

23.

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COMMUNICATIONS

0. H., ROSEBROUGH, N. J., FARR, L. A., AND RANDALL, R. J., .I. BioZ. Chem. 193, 262 (1951). ROBINSON, H. W., AND HOYDEN, C. G., J. Biol. Chem. 135, 707 (1940). JACKSON, H., AND KENDAL, L. P., Biochem. J. 44, 477 (1949). MASON, H. S., AND PETERSON, E. W., J. B&Z. Chem. 212, 435 (1955). SMITH, J. L., AND KRUEGER, R. C., J. Bid. Chum. 237, 1121 (1962). MACRAE, A. R., AND DUGGLEBY, R. G., Phytochemistry 7, 855 (1968). ASIMOV, I., AND DAWSON, C. R., J. Am. Chem. Sot. 72, 820 (1950). ING~EAHAM, L. L., f. Am. Chem. Sot. ‘76, 3777 (19.54). MAYBERRY, J. M., AND MALLETTE, M. R.. J. Gen Physiol. 45, 1239 (1962). EADIE, G. S., Science 116, 688 (1952). LOWRY,

M. YAMAGUCH? H. M. HENDRRSON P. M. HWANG J. D. CAMPBELL Departments of Plant Science and Food Science University of Manitoba Winnipeg, Canada Received April 18,1969 ‘On leave during 1967-63 from t.he University of California address: University of California. Davis, California, 95616.

A Sample

Injection Liquid

Valve

at Davis. Present

for Use in High-Pressure

Chromatography1

During the past two years, several liquid chromatographic systems t,hat operate at pressures in excess of 1000 psi have been developed (l-3). Two high-resolution analytical systems for body fluids analyses using high-pressure ion-exchange chromatography have been designed for operation up to 5000 psi (1, 2). In order to automate such systems, we must first devise a sample introduction technique that does not interfere with the operation of the chromatograph. In high-pressure liquid chromatography, this necessitates injecting the sample mixture directly into the high-pressure eluent stream just ahead of the chromatographic column. Use of a Sample Injection Valve. One way of introducing the sample ‘Research supported by the National the U. S. Atomic Energy Commkion.

Institute

of General

Medical

Sciences and

SHORT

183

COMMUNICATIONS

directly into the high-pressure eluent stream is to use a sample injection valve that provides a means for switching a prefilled sample loop into the column eluent line. Valves of this type have been employed in gas chromatography for some time, and a sample injection valve for use in liquid systems (Hoke Company, Part No. 30213-l) is now commercially available. However, none of these valves is capable of operation at liquid pressures greater than 2000 psi without leaking. At Oak Ridge National Laboratory, we recently designed and successfully tested a six-port sample injection valve that will operate at liquid pressures up to 5000 psi for extended periods of time. Description of Valve. The new valve has six ports, with attached t.ubing, spaced equidistantly around a metal cylindrical sleeve (Fig. 1). Each of the three pairs of ports is connected by small slots machined in the plastic (Delrin) cylindrical sleeve that rotates inside the metal sleeve. Rotation of the inner sleeve allows the slots to move and connect different port,s. This permits t,he valve to operate in the two positions necessary for sample injection. A unique feature of this valve is t’he special type of seal used to separate the high-pressure side of the valve from ambient pressure. The inner plastic sleeve is held on a tapered metal shaft that has a fixed restraint MOVABLE

METiL

WASHER

CONNECTING

SLOT TUBING ATTACliED ACCESS PORTS

TO

NUT FOR TIGHT PLASTIC SLEEV METAL

CYLINDER

TAPERED

FIG. 1. A so00 pi.

small,

six-port

sample

injection

METAL

SHAFT

HANDLE

FOR ROTATING

SHAFT

F, ‘ve

capable

operation

of

up

to

184

SHORT COMMUNICATIONS

on one side and a movable metal washer on the other side. The washer is forced against the plastic by a nut located on the threaded end of the metal shaft. This action drives the plastic sleeve up the shaft and against the outer metal sleeve, thereby providing a seal between each port. Additional force can be exerted on the plastic by further tightening the nut. The metal restraints on each end of the shaft, as well as the outer metal sleeve, prevent the plastic from deforming. The valve has been tested for over 4000 hr at pressures up to 5000 psi on a prototype analyzer that is being used to resolve, detect, and quantify the UV-absorbing constituents of body fluids (4). About 200 samples were injected during this period and no leaks occurred. The valve can be operated either by hand pressure or by a motorized control. A complete set of construction prints for this valve is available as CAPE-1853 form the Clearinghouse for Federal Scientific and Technical Information, U. S. Department of Commerce, 5285 Port Royal Road, Springfield, .Virginia 22151. REFERENCES 1. SCOTT, C.D., Clin. Chem.14, 521 (1968). 2. JOLLEY, R.L., AND FBEEMAN, M.L., CEin. Chem. 14,538 (1968). 3. FELTON, H., J. Chromatog. Xci. 7, 13 (1969). 4. SCOTT, C. D., JOLLEY, R. L., PITT, W. W., AND JOHNSON, W. F., paper presented at the First Annual Symposium on Automated, High Resolution Analyses in the Clinical Laboratory, held at Oak Ridge National Laboratory, Oak Ridge, Tennessee, March 13-14, 1969; to be published in a supplement to American Journal

of Clinical

Pathology.

CHARLES D. SCOTT WAYNE F. JOHNSON VERNON E. WALKER Oak Ridge Oak Ridge, Received

*Operated Corporation.

National

Laboratory” Tennessee 37830 April W,l969

for

the

U.

S. Atomic

Energy

Commission

by

Union

Carbide