I'm not sure what your question is asking for? The purpose of acid digestion is to break down the sample matrix and dissolve the solid materials, removing the carbon structures such as protein and fats. Heating the sample in acid will boil off the acid and break down the organic materials. You will not want all that acid to remain in the solution as it will be too viscous to aspirate through the burner of the AAS. The preference is for enough acid to keep the metals in solution, but not so much that it creates matrix problems.

Personally I would avoid filtering the sample especially through filter paper, as this adds several potential sources of contamination, particularly if you are interested in trace elements (ie the paper itself, the bottles you pour into, the funnel the paper sits in and the gloves you wear while doing this all contribute to sources of error.)

You might also like to try a method like this: Article Measurement of haem and total iron in fish, shrimp and prawn...

Hello, for better sample prep and avoiding evaporation of acids you need to use closed systems like teflon tubes and microwave digestion system.

microwave digestion system is very efficent: less chemicals and environmental problems.