Typical chromatograms from open tubular columns coated with (a) poly-dimethyl siloxane; (b) 5 (phenylmenthyldimenthyl) siloxane; (c) 50 (phenylmenthyldimenthyl) siloxane; (d) 50% poly(trifluoropropyl-dimethyl) siloxane; (e) polyethylene glycol; (f) 50% poly(cyanopropyl-dimethyl) siloxane.