The lyophilized powder of this standard is not soluble in water. Standard dissolving instruction: Use ethanol (99.5 %) or methanol to prepare a concentrated (stock) solution of THP standard. This solution can be stored for longer time in a sealed tube.Working solution can be used daily but needs to be changed after one month.Working solution is used to prepare standard points 0-200 pg. It needs to be dried under nitrogen before it is diluted in water based soltion, otherwise the steroid will oxidase.Following dyring, water based solution can be added to this standard.