I n general, the extractor facilitates, with a minimum of handling, the laboratory extraction of small quantities of material from large volumes of solution. It is possible to control the percentage removal of a solute within wide limits by changing the ratio of rates Of and the under extraction.
LITERATURE CITED
(1) Fricke, H. K., Glas-Instr.-Tech. 3,
w.H., proc., Hot Labs and Equipment Conference, pp. 98-102, Philadelphia (1957). (3) Hoffmann-La Roche &L co., -4.-G., Brit. Patent 791025 (February 19, 1958). (4) Jensen, K. J., Bane, R. W., Analyst 82,67-70 (1957). (2)295-6 ill, ( lg5’). K. H., Adams,
(5) Morrison, G. H., Freiser, H., AXAL, CHEY. 30, 632 (19%). (6) Ibid., 32, No. 5 , 3iR-4iR (1960). (7) Niederl, J. B., Niederl, Victor, “b1icromethods of Quantitative Organic Analysis,” 2nd ed., p. 114, Wiley, New York, 1948. (8)Poh4 F. A,, 2. 3 n a l . Chem. 157, 6-13 (1957). (9) Treybal, R. E., Ind. Eng. Chem. 51, 378-58 (1959).
Collection of Gas liquid Chromatography Fractions by Gradient Cooling Hermann Schlenk and D. M. Sand, The Hormel Institute, University of Minnesota, Austin, Minn.
HE
device shown in Figure 1 is used
I
Troutinely at this laboratory for col-
lecting long-chain fatty esters by gas liquid chromatography (GLC).
1676
ANALYTICAL CHEMISTRY
DETECTOR
n
OUTER GLASS
A Beckman GC-2 apparatus with a thermoconductivity detector is used a t 236’ C. w e h an inlet temperature of about 300 C. The column is an aluminum tubing, 9 . 5 m m . 0.d. and 310 cm. long (3/rinch X 10 feet), packed with 20% p-cyclodextrin acetate (a,3) on Chromosorb R, 30 to 60 mesh, and holds about 20 grams of organic phase. Flow rates are betn-een 120 and 150 cc. of He per minute and sample sizes are between 30 and 100 mg., depending upon the separation involved. The vapors leave the detector and enter the collecting tube inside the oven; they are cooled to about room temperature at a distance of 10 t o 15 cm. from the outlet. The esters condense as droplets after the first 3 cm. of the glass tubing and form a thin film in the adjacent area of the temperature gradient. After about 10 cm. they are not condensed any more. The fog which escapes the first condensation step is heated again and condenses as droplets and film over a length of 6 to 8 cm. in the area of the second temperature gradient. About 15yo of the total is found in this area of condensation. Fogging is not observed a t the end of the tube, but it occurs unavoidably without the auxiliary heater or when a cold tube is inserted in collecting different fractions. The glass tubes must be preheated and are changed by hand within a few seconds. They are pressed tightly t o the silicone rubber disks by two rubber bands and hooks (not shown in Figure 1) which are mounted to the casing of the GLC apparatus. After an autosi-
a
TUBING 120 CM.
BMM.
CASING
150 “C.
230’C.
COPPER
5 5 CM.
I_
I
30CM.
Figure 1 . Fraction collector for high-temperature GLC, adjusted to Beckman GC-2 apparatus
dizable fraction has been colllected, the glass is flushed n i t h K2 from the cold end immediately upon disconnection until the material has cooled and can be rinsed out. Recoveries mere determined by injecting 55 to 57 mg. of oleate, linoleate, linolenate, or arachidonate. Each run was carried out in duplicate, and 51 to 54 nig. of the esters were recovered in all experiments. -iccordingly, the recoveries were 90 to 95% of the amount injected. Before starting a preparative run, it is advisable t o flush the system with 50 mg. of methyl myristate when the column has been at high teniperature for several hours unused, or has been used shortly before with a sample of highly unsaturated esters. Infrared spectra, repeated GLC, and
other analytical tests do not detect contaminants from the phase. Ozonization and subsequent procedures show that unsaturated esters collected from GLC under these conditions retain their original structure. This appears to be the case even with a docosapmtaenoate ( 1 ) . LITERATURE CITED
(1) Haines, T. H., Aaronson, S., Gellerman. J. L.. Schlenk, H.. Nature 194, I
,
1282 (1962):
(2) Sand, D. X., Schlenk, H., ANAL. CHEM.33, 1624 (1961). (3) Schlenk, H., Gellerman, J. L., Sand, D. M., Ibid., 34, 1529 (1962).
WORK supported by a research grant from the National Institutes of Health (USPHS H-5363) and by The Hormel Foundation.
