How should I make my standard pre-dilutions? It is not very clear from the Chromogenix Coamatic® Antithrombin package insert.

A suggested method for the predilution, although it cab be up to the analyst what volumes to use:

100%: 400 ul normal plasma, 0 ul Saline
75%: 300 ul normal plasma, 100 ul Saline
50%: 200 ul normal plasma, 200 ul Saline
25%: 100 ul normal plasma, 300 ul Saline

From here, follow the package insert.