Purification by Automatic Gas Chromatography

A completely automatic apparatus has been developed for the preparative-scale purification of compounds by gas-liquid chromatography. A clock timer periodically activates a pump that injects a sample into the column. The recording potentiometer on which the chromatogram is traced has a switch mounted at the upper margin. Collection of the purified main component occurs when the recorder pen goes to the end of the scale and trips the switch. The sensitivity of the detector bridge circuit is adjusted so that only the trace caused by the major component will activate the collection process. Toluene, ethylbenzene, and mesitylene were purified with the apparatus. Best results were obtained with toluene. In one pass through the apparatus, 92 percent of the impurities were removed from the toluene and the purified product was collected at a rate of 25 ml of liquid per day.