Sample Preparation. The plant materials and the dietary supplements were ground and homogenized to obtain a uniform matrix. The dietary supplements were in the form of capsules or tablets.Ten capsules or tablets were weighed for each sample, and the average was taken for the weight of each capsule or tablet of the sample.About 500 mg of plant sample or equivalent amount for the dietary The n-hexane was evaporated to dryness, and the residue was then
dissolved in 250 μL of methylene chloride and 150 μL of methanol.Fifty microliters of internal standard (25.64 μg/mL) and 50 μL of trimethylsulfonium hydroxide were added to the solution. Duplicate samples were extracted, and two injections were made for each sample.The content of each ginkgolic acid was reported as a mean value of the test results.