Purification and Analysis by Gas Chromatography The crude limonene is purified by preparative GC using a 20% Carbowax column (0.25-in. OD x 8-R. long) operated at approximately 180"C. Resolution of the limonene can be achieved with injections of at least 25 pL (and usually 50 pL). (See figure.) Generally, it is not necessary to wait for any late-eluting materials to clear the instrument before re-injecting. The limonene is collected in a tared tube and the process is repeated until all of the crude oil has been purified, which
