Thymol detection and quantitation by solid-phase microextraction in faeces and egg yolk of Japanese quail

To measure bioavailability of the active ingredients of phytogenic feed additives in poultry products and subproducts is a key element for developing a rational understanding of its mode of action and biological effects. Hence, we validated a headspace solid phase microextraction (HS-SPME) technique followed by gas chromatography-mass spectrometry as an analytical extraction procedure and as method for detection and quantitation of 2-Isopropyl-5-methylphenol (thymol) in faeces and egg yolk of quail. The suitability of this method for thymol analysis in both matrices was first proved via linearity, limit of detection, limit of quantification, and recovery using m-cresol as internal standard. The optimal HS-SPME extraction conditions were obtained at 40°C for 5min in faeces and 60°C for 30min in egg yolk. This procedure was found to be precise, sensitive and linear in the range of 2.5-100ng/gr for faeces and 20-800ng/gr for the egg yolk. Limits of detection were 0.5ng/g and 5ng/g for faeces and yolk, respectively, and the limits of quantitation were 1ng/g and 10ng/g for faeces and yolk, respectively. The method was successfully used for measuring thymol in fecal and egg yolk samples, from quails supplemented with thymol in their diets. Thus, in fresh faeces and egg yolk samples obtained from a supplemented group (80mg thymol per bird per day) were determined as 31.51ng/g for faeces and 11.83ng/g for the egg yolk.