Abstract: The Head-space solid phase microextraction conditions for analysis octanoic acid and capric acid in beer were optimized by SAS software combined with Plackett-Burman design and the response surface analysis. The optimal conditions were as follows:extract temperature 51.32 ℃, extract time 42.23 min and salt dosage 0.51 g/ml. This method had a better duplication and a higher recovery. The relative standard deviations (RSD) of peak areas for fatty acids were less than 4%, the detection limits of octanoic acid and capric acid was 4.04 μg/L and 0.046 μg/L, respectively, and the working curve linear scope was 0.404～ 8080 mg/L and 0.046～920 mg/L, respectively, with correlation coefficient more than 0.999.

Key words: head-space solid microextraction (HS-SPME), gas chromatography (GC), beer, fatty acids (FAs), response surface analysis (RSA), Plackett-Burman design