From the information available for the preparation to be assayed ( the “ unknown ” ) , assign to it an assumed potency per unit weight or volume , and on this assumption prepare on the day of the assay a stock solution and test dilution as specified for each antibiotic but with the same final diluent as used for the usp reference standard . the assay with 5levels of the standard requires only one level of the unknown at a concentration assumed equal to the median level of the standard 根据有效的信息制备试验溶液，指定一个假定的每单位重量的效价或者体积，然后在假设的基础制备当天储备液试验和稀释溶液作为每一种抗生素指定的效价，但是当使用相同usp参考标准品的最终稀释液时，试验应使用平行5的标准要求仅有一份未知的做为浓度等同于中部的标准。
