Ezra S. Alhadeff
An Applicator for Preparative TLC
university of California Riverside, 92502
The applicator consists of two frames built from aluminum rods ( I / % in. diameter lattice rods) which are supported on a piece of varnished plywood J / r in. X 12 in. X 18 in. One frame serves to prevent contact between the air hose (1/4-in. latex laboratory tubing) and the tlc plate. The other frame supports the carriage on which a 'lrml syringe (Yale, cc, Tuberculin) is attached. The syringe is mounted inside a short piece of copper tubing in. 0.d.) using three gaskets cut, from '/4-in. Tygon tubing, and the copper tube is attached to the carriage by means of a lattice connector. The carriage is constructed of '/xin. thick aluminum strips and six steel ball bearings (Delco #77R2A (I/%in. o.d. and in. id.) shielded ball bearings are suitable for this purpose). The top flange of the syringe is cut off with a glass saw in order to be able to connect the syringe to the air hose via a T-tube ('/a in. 0.d.). A fine needle (28-30 gauge) is used with the syringe, and new needles are deburred
-
Overall (center1 ond detailed views of the p l d e opplxofor.
with a fine metal wire before using. A small glass wool plug is inserted in the syringe to filter off any particles from the solution which could clog up the fine needle, or the solution can be filtered before loading it in the syringe. The figure shows the details of the device. The solution to be analyzed is injected through the open end of the T-tube into the syringe by means of a second syringe (1 or 2 ml) with a long needle (22 gauge, 2 in.). During deposition, the solution is driven out by a steady stream of compressed air. The streaking of a chromatoplate can he started once the plate is positioned against the fixed wooden ruler which is fastened on the stage by means of epoxy glue. The carriage is moved off the tlc plate, the syringe is loaded and the index finger is made to rest on the open end of the T-tube while a gentle stream of air is allowed to flow through the air hose. The carriage is then made to move rapidly back and forth, until most of the solution is spread on the plate. After streaking the chromatoplate, the syringe and the needle can be cleaned by rinsing them a few times with acetone or chloroform added through the open end of the T-tube and expelled through the needle. This device was used in the isomerization of mesoand DL-1,2-dimethoxy-1,2-diphenylethane. The products were readily resolved on Silica Gel G using ethanol-free chloroform even though some of the R, values for the compounds obtained were nearly similar.
Volume 46, Number 4, April 1969
/
249
