Depends on several factors. 4-Methyl-2-pentanol and 2-octanol are the most "universal" and good approaches for most GC-MS analysis, depending of course of the specific requirements to be used as IS, namely the sctrutural similarity towards the target compounds and a different RT. In your case I supose that phenol and 2-phenyletanol can be good options.

Thanks a lot José. I'll definitely try using that

You Welcome!

Best wishes for your research endeavours.

You can use any volatile organic solvent, other than veratryl and vanillyl alcohol for  the GC-MS calibration. Do u know how to calculate ? 

You can use any volatile organic solvent, other than veratryl and vanillyl alcohol for  the GC-MS calibration. Do u know how to calculate ? 

Yes I have used organics before. Volatile organics are not very accurate due to low vapor pressure. I am keen to avoid those since the Shimadzu is very accurate. Thanks though