How to perform assay test on suspension injection by pool sample

   My QC division got the problem when they pool the sample from small vial. Some of API was still attached at vial wall so that the  result was less than an actual label amount. Then they try to rinse the vial that cause the concentration was different from original concentration.

please guide me the method

Try pooling based on equal weights. This assumes the dosage form/drug product is homogenous even though it is suspended.

If this is a wrong assumption you have a ‘bigger’ problem! You will not pass ‘content uniformity’.

I also presume you are selecting the samples based on statistics.

But i have the pouring problem when try to transfer 1 ml suspension from 2 ml-vial size

Weigh the same vial before extraction, then after extraction. The difference in weight is the amount of suspended material you pooled.

this will get only weight of all suspension but i need to know weight of API
should i get the density before??

Not required. Just perform your calculations in mass units like mg, ug, or ng. Concentration will be in mass/mL. Final assay will be mass/mL x total volume in mL = mass