Manifold for Gas Chromatography Alfred R. Conklln,Jr. Wilmington College, Wilmington, OH 45177 Over a period of a dozen or so vears. the Chemistrv Department nt Wilmington College hhas c u l l & d a number;fgas chn~mntopraphs.We have two thermal conducti\~icsand two flame ionkaiion detector instruments. With the addition of each gas chromatograph, we needed from one to three tanks of gas, regulators, traps, etc. There were eight tanks of gas around the one table on which the instruments were located. Clearly, this setup was unmanageable. We could not go on adding instruments and tanks of gas in this manner. Thus, we developed a manifold that allows us to operate all four gas chromatographs on only three tanks, one of hydrogen and one of compressed air for the flame ionization detectors, and one tank of carrier gas. In actuality, we have the manifold setup to accept an additional tank of carrier gas. This gives us the flexibility of avariety of carrier gases, i.e., either N p or He, or a back-up of carrier gas, so that while one tank is filled, the other can he used. The tanks are positioned a t one end of the table with three ?b in. copper tubing lines running down the middle of the table (see figure 1).We have fabricated a trap for each tank from %-in. pipe filled I12 with molecular sieve and I12 with drierite. The traps and pas lines are color coded to match the tanks as much u s possil;lr. The hydrogen line is red, the air line yellow. and the carrier gas line oranpe. At the tank end of the table, the carrier gas line makes at& with one arm to each of the two carrier gas tanks. Typically, we keep one tank of nitrogen and one tank of helium on hand a t all times. Since we use nitrogen as a carrier gas most often, the arm of the tee going to this tank has a valve in it, such that the tank can be removed without disrupting the flow of carrier gas. At each gas chromatograph the carrier gas line is fitted with a valve and a line to the instrument. In addition, there are valves in the hvdrocen ., and com~ressedair lines at each flame ionization detector instrument. At the end of the tahle,away from rhe tanks. each lineendsina valve with a nionlc so that we are able to bhtain samples of these gases for 'dkmonstrations, experiments, or research as the need arises. The tanks need not be disconnected for anything but filling. In addition, this gives us the option of adding another gas chromatograph with little remodeling of the existing system. The gas chromatographs attached to this manifold are used by the organic chemistry laboratory. In this situation the students need not use the maximum sensitivity of the instruments. We have under these circumstances operated two thermal conductivity instruments and one flame ionization instrument simultaneously without one instrument having an observable effect on another. However, under more demanding situations, only one instrument is operated a t a time.
This setup has been very useful in cutting down the number of tanks and associated equipment. I t has also allowed us a neater and more compact arrangement of equipment. In addition, we are able to obtain any of these gases for any other purpose we desire. Acknowledgment The author wishes to thank Susan Dean and Margaret Keane for their assistance in putting this piece of equipment toeether.
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616
Journal of Chemical Education
Manifold far gas chromatography showing traps, lines, and valves
