A New Design for Gas Chromatography Columns S. A. Ryce and W. A. Bryce, Department of Chemistry, University of British Columbia, Vancouver 8, B. C.
columns are G usually shaped as U-tubes, compact spirals, or as single or multiple loops. AS CHROMATOGWHY
Certain disadvantages are inherent in
each of these designs. An assembly of U-tube columns of the length required for certain separations requires a considerable amount of space and is difficult to thermostat satisfactorily. The filling and winding of spiral or tightly coiled columns presents a number of problems of a purely mechanical nature. There is also the danger with spirals that channelling may occur with a consequent reduction in column efficiency. Nonuniform packing is Virtnally impossible to detect in a metal column. A column design has been developed in this laboratory which retains the advantages with respect to uniformity of packing of the simple U-tube and at the same t i e enables a long column to be contained in a comparatively small volume. An additional advantage of the design is that the column length is adjustable so that any fraction of the total length of the column may be used for a particular separation. The external features of the column 1 in Fimire 1. Lengths of inches
Figure 1. of column
External features
manifold is held in place by metal screws and can be removed for filling the individual column sections. Uniformity in packing is achieved with no difficulty due to the shortness of the sections. A rubher gasket ensures a tight seal between the manifold and the lid. The details of the channels in the upper manifold are shown in Figure 2. In addition to the permanent outlet at the end of the column, shown to the left of the curved inlet tube in Figure 1, there is a movable outlet which can be
b
m
Figure 2. Details of channels in upper manifold and of movable outlet
tapped into the column at either one third or two thirds of the total length. This outlet has attached to it a small rubher and metal plug which projects into the appropriate length of column when the movable outlet is in position and seals off the unused series of columns. The details of the movable outlet are shown in Figure 2b. The column assembly shown in Figure 1has an over-all length of 32 feet and is tapped at 10- and 20-foot lengths. The entire assembly is only 9 inches high and 4*/* inches in diameter. A column of this shape fits readily into a large Dewar for thermostatting. The gasket can he made of Teflon or silicone rubher for high temperature operation. ACKNOWLEDGMENT
We are grateful to Rudolf Muehlchen for constructing the column.
New Technique for Pyrolyzing Samples for Gas Chromatographic Analysis William 8. Swann and James P. Dux, Research and Development Division, American Viscose Corp., Marcus Hook. Po.
major limitation in the applica-
HE
Ttion of gas chromatography to chemical analysis is the requirement that
the sample be a gas or liquid with moderately high vapor pressure. The most successful method of circumventing this:difficulty which has appeared in the literature is the use of thermal , .. of" samples, > n.. aegraaauon Iouoweu ~y gas chromatography of the light fragments produced. The chromatogram produced is frequently specific for the material pyrolyzed, and thus serves as a qualitative identification of the sample (8). The technique has been 1
654
1,
ANALYTICAL CHEMISTRY
used for polymers (f, d , 4 ) and complex, nonpolymeric materials (d), and has been applied as a quantitative analytical technique for the analysis of copolymers (4). The most difficult technical problem in this method is the introduction of the pyrolyzed fragments into the carrier I ._. I ._ r.. smeam 01 me gas cnrurnawg~apn. 111 general, two procedures are used. In the first, the pyrolytic fragments are condensed in a cold trap of some sort and then introduced in the usual manner into the inlet of the chromatograph. In the second, a minute quantity of the ,I
1.
~
polymer is pyrolyzed on a filament which is placed in the inlet stream of the instrument and heated by an electric current. This paper describes a technique which the authors feel is superior to either of these methods. The technique has been successfully applied I^
LIU
'I^ :.l-..':e--L:-.e ^_A u e ~ u c i m w i ~ i i l l i iVI~ u puiyuiellua m u
to copolymer analysis in these lahoratories. A sampleof 50 mg. of powdered palmer is placed in a 1-inch length of 4m. glass tubing sealed at one end. The sample tube is then placed in a
