Samples were extracted and introduced into the GC–MS using
headspace SPME using a 1 cm long fibre (Supelco, Bellefonte, PA,
USA) that was coated with a 65 lm layer of polydimethylsiloxane/
divinylbenzene and housed in a 23 gauge needle. The SPME fibre
was exposed to the headspace of a sample of ghee (3 g) in a
20 ml Chromacol (Welwyn Garden City, Herts, UK) volatile organic
compound (VOC) tube sealed with Teflon-backed septa (Chromacol).
The headspace was extracted for 30 min at 60 C with shaking
at 250 rpm. Analytes were desorbed from the SPME fibre in the GC
injection port, which contained a silanised SPME liner (Restek) and
was held at 220 C. The split injection technique was used to inject
sample with a 5:1 split ratio. The column flow (Helium carrier gas)
was 1 ml min1, with a purge flow of 3 ml min1.