The temperatures used in injector and detector was 280 and 320 ◦C, respectively. Samples of 1.0 ไมโครลิตร were injected adopting a split ratio of 1:50. The carrier gas used was the hydrogen with linear speed of 40 mL/min. The phytosterols (colestherol, campesterol, stigmasterol, เบต้า-sitosterol and stigmastanol) were identified by comparison with the retention time of pure standards (Supelco, Bellefonte, USA) analyzed under the same conditions of the samples. The quantification of each isomer was performed by standardizing internal (5-cholestano-3-ol) based on the areas of the peaks.