I want to calibrate C3-C4 oxygenates for GC-FID (packed) and I would like to know what is the most effective method. Most of the compounds of interest have boilling point from 20-80 oC. The samples I will have to analyze will be in gas phase from a pipe connected to the gc valve. If I use a gas mixture I will not be able to identify the peaks of each analyte. Moreover, a mix like that it would probably not be stable even in small concentrations. Could I make calibration from liquid standards with injection by a syringe? In a previous respond an expert recomment that I would better use permeation tubes. In that case is the use of gas standard generator necessary? What about the cost of a generator?