A Simple Streaker for Preparative Layer Chromatography I n this communication, we describe an inexpensive, reliable streaker for preparative thin layer chromatography which has been used in our undergraduate organic laboratory courses 8s well as in our research efforts (ssimilar device will be available fromKontes Glass Company, Vineland, N. J.). Basicdly, thestreaker is a modifiedversionof the onc described by Monteiro [ J .Chl-omalog., 18, 594 (1965)l and is shown in the photograph and drawing. The device consists of a base and a capillary loosely hanging from a reservoir. The base has been designed to run dong t,he edge of a counter while holding the capillary just in contact with the s u p face of the layer.
The method used in streaking is as follows: The streaking device is placed over the edge of the counter. The tlc plate is then placed parallel to the edge of the counter and such that the st,reak will be approximstely 1 in. from the bottom of t,he ~ l s t e . The heieht of the reservoir is adiusted so as to brins the cs~illarviust into contact with the edge of the counter as a. guide. The rate of streaking e m be varied by changing the bore of the capillary. We have found bores of f ~ o m0.017 to 0.020 in. to be optimal. However, other factors also affect the rate. If the reservoir is held close to horizontal, an i l ~ i. k should v not be below even rate is obtained. We have settled on an anale .5' from horizontal. The tip of the C . the bottom of the reservoir 53 siphoning occurs and uneven streaking can result. Bv " u i n e this device. undereraduates routinelv have been able to obtain narrow. straieht streaks on olatev 2-36 in. long. Preparative thin iayer c&omatography can thus be irhmduced as s routine, celiabie method of separation very early in the students' training. We thank the donors of the Petroleum Resemch Fond, administered by the American Chemical Society (LJA), Eli Lilly and Company (LJA), and the Nstionsl Institutes of Health of the U. S. Public Health Service, Grant No. GM-11309 (JRT) for partial support of this research.
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Journal of Chemicol Educofion
