InertCap 225 manufactured by GL Sciences Inc. is a medium polar column bonded 50 % cyanopropylmethyl and 50 % phenylmethylpolysiloxane. Cyano group in the stationary phase includes triple bond and retains compounds stronger in accordance with the increase of the number of unsaturated bond by their dipole/dipole interactions. For that reason InertCap 225 shows high separation efficiency for analyses of geometrical isomers.