This is a quick guide for routine quantitative analysis of sesquiterpenoids in dodecane using an autosampler-assisted gas chromatograph. This protocol has been established in the Lindberg lab at Ångström laboratory (Uppsala University) for direct analysis of dodecane-based ex-situ extracts from cyanobacterial strains producing different types of sesquiterpenoids. The basic protocol was originally described in the master thesis of Sara Nilsson for (E)-α-bisabolene quantification [1], and has been extended to (-)-α-bisabolol and (-)-patchoulol. This protocol describes the pipeline from the general setup to the generation of quantitative data output for external data processing (e.g. in Excel). Qualitative data analysis is not described. [1] Nilsson, S. (2017). (E)-α-bisabolene production in Synechocystis sp. PCC 6803 (Master thesis). Retrieved from http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-325811