2.2. GC analysis2.2.1. GC-FID analysis of essential oilsGC and GC–MS analyses were done as per our previous report(Pragadheesh et al., 2013). Characterization was achieved on thebasis of retention time, elution order, relative retention indexusing a homologous series of n-alkanes (C6–C28hydrocarbons,Polyscience Corp. Niles IL), coinjection with standards in GC-FIDcapillary column (Aldrich and Fluka), mass spectra library search(NIST/EPA/NIH version 2.1 and Wiley registry of mass spectral data7th edition) and by comparing with the mass spectral literaturedata (Adams, 1995). The relative amounts of individual componentswere calculated based on GC peak areas without using correctionfactors.2.2.2. SPME-GC-FID analysis of headspace of Petri-plateSPME-GC-FID analysis was done as described earlier(Pragadheesh et al., 2013). The SPME fiber (DVB/CAR/PDMS)was exposed to heated injector for 1 h at 270◦C prior to adsorp-tion. The activated fiber was then exposed to headspace ofPetri-plate containing essential oil for 15 min followed by desorp-tion to heated injector. The validation of SPME fiber was carried outwith respect to the camphor concentration and time of exposure.