Secondary standard is required to improve the accuracy of drug concentration and has an intermediate drug concentration. For the preparation of secondary standard, dilution of primary standard is carried out. 

Typically, a diluent can be mixture of methanol and water (e.g. 75:25 %v/v) is suitable for our biorelevant media if the drug substance is neutral. For pH sensitive drugs, an appropriate buffer can be used instead of water to increase the solubility of drug in the secondary standard. 

Secondary standard preparation

• Prepare diluent: methanol with water (buffered or unbuffered) mixture 
• Select the size of volumetric flask 
• Transfer required volume of PS into selected volumetric flask
• Make up to volume with diluent 
• Record the final concentration

Use secondary standard preparation calculator to find out how much volume of primary standard is required to prepare the secondary standard and what will be the concentration of Secondary standard.

Download our Biorelevant Dissolution Guides here.