A Simple and Inexpensive Collector for Preparative Gas Chromatography In the m u m of a study involving the alkylation of naphthalene with alkenes the isolation of monoalkylnaphthalenes by gas chromatography was required (1). These were high boiling materials (hp 140-155°C (2 mm)) with a tendency for aemsol formation. A number of methods for the isolation of samples from gas chromatographs are available. These indude filter methods in which the sample is sorbed on an inert support (2), solvent e n t r a h k e n t (3),cold traps (4). electrnstatic precipitation and other devices (5). For our purposes these were not useful for a variety of reasons. Many of the methods were inconvenient because of the somewhat complicated techniques. In some eases the methods were ineffective due to aerosol formation of our compounds. In other cases the changing of sample collectors was lengthy and cumbersome. Other methods allowed collection of only very limited amounts of sample. The technique described here utilizes a very simple and inexpensive collection device that gave isolated yields of monoalkylnaphthalenes of generally better than 90%. A coarse gas dispersion tuhe (bubbler) of the cylinder type consisting of a glass tube (8 mm od x 250 mm) with a fritted cylinder (12 mm od) fused onto the lower end was used. This is svailahle fmm most supply houses. A right angle bend was made in the glass at a point 180 mm from thefritted end. The open end of the glass tube was drawn down to about 3 mm diameter. This could be readily inserted into the outlet of our chmmatograph (Varian-Aeragraph Madel 1520) through a commercially available collection gasket. This gasket consisted of a %-in. diameter x %-in. thick silicone rubber disk with a %-in. diameter center hole connected to the outlet of the chromatograph with a nut. The fritted end of the bubbler was immersed in 10 ml of hexane or acetone contained in a 150 x 18mm (od) test tuhe. A series d bubblers with the fritted ends in hexane could be conveniently prepared before a collection run was started. Changing collectors could be readily accomplished in ahaut 1s. Sample size ranged from 1to 1W mg for single injections. Multiple as well as single injections were carried out, and samples ranging from 8 to 700 mg were collected. After evaporation of solvent the isolated samples were sufficiently pure for elemental analysis and examination by mass spectrometry, nmr, and ir spectroscopy. ~~~~~~~
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Literature Cited 11) Friedman, H . M . , andRothbc.g,I..J. Or#.Chpm.. Manus"iptsubmittd. (21 hggon, H. W.,AMI. c h m , a,1 ~ 5 1 1 9 6 1 )naira. . A. K., and adi in, N.s., J. w d ~3,131 ~ ~(196%). . , witte, K., and~issingcr, O.,Z A M I c h m , 238, 119 (1968). Schluter, E. C . , A d . Chem.. 41. 1360 (1969). Witiak, J.L., Junk, G. A., Calder. G.V.. Fritz, J. S.. and Svec, H. J., J OR. Chom.. 88,3066 , . \ .a ,"m ,.,,
(3) Hardy, R.. and Kesy. J . N.. J Chmmotogr. IT. 177 11965). ( I ) Bsdinm, H. T., and Wassink, J. G., J Chmmdogr., 18.159 (1965). Bsllinger, J.T., Bart&. T. T., andTaylor, J. H., J Chmmdogr. Sri, 6.295 11968). (6, Fish.. D. W.. and Cmbv. D. 0.. J Chmmotosr.. 11968).Thornoaon. A. E.. J. Chmmofoar. 6.454 (1961).Teranishi. R.. Corse. J. W.. Day, 8 . C . and . . 31.307 . Jenningn, W, G.,J. Chmrnofogr., 9, Z44 119621. Stevens, R. K., &d Mold, J. D., J. dhr&ologr., 10. 399 (1963). Svaboda P. A. T., Nature, 199. 31 (1961). Hornstein, I.,sndCrowe. P.,Anal. Chsm.. 3'7,17011965).
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Irvin Rothberg
H.Martin Friedman Rutgers University Newark,New Jersey 07102
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Journal of Chemical Edocafion
