[AussieKenDoll]

Many chemical (e.g. :- digestion of samples) and / or physical methods are used to modify the matrix.

as an example, Determination of Cd in rice grain using GFAAS : rice grains are digested using microwave acid digestion (Nitric acid and hydrochloric acid) and subsequently treated with Pd-Mg nitrate matrix modifier.

[Corribus]

Not 100% sure what your question is. You asked a question in your title, but then kind of answered it in your post.