Aliquots (100 lL) of the AR extract were placed in a glass-stoppered test tube and trimethylsilyl ether derivates of the AR were prepared by adding 100 lL of BSA + TMCS + TMSI silylating reagent. The tubes were shaken to properly mix the sample in the reagent and then heated at 65 C for 30 min. Any excess reagent was then removed under nitrogen, and the residue was re-dissolved in hexane (1 mL) and stored at 20 C for no more than 1 week. All the working standard solutions were freshly prepared daily prior to use.