here is my understanding...
let's say you make up a std at a known conc. in the matrix, then inject at different volumes, even though the vol is different the amount of matrix is the same...right!
When you inject variable amounts of your matrix (as in serial dlituions!) at a given injection volume and see that it effects the response of your std, then what do you do?
Plese let me know if I am totally wrong about this concept of matrix.
thank you
Vansuela

I am not sure I completely understand your question but ... If you prepare a mixture of the standard and matrix and inject different volumes, although the ratio of active ingredient (from the standard) to the matrix remains constant, the amount of matrix injected onto the column is not constant. Consider a standard plus matrix mixture containing 10 ug matrix / uL. Injecting 10 uL puts 100 ug matrix onto the column while injecting 20 uL puts 200 ug matrix onto the column, just as doubling the concentration in a serial dilution doubles the amount injected when constant injection volumes are used. However, by doubling the injection volume, you also double the amount of the active ingredients from the standard that are injected onto the column so any matrix interferences may not be as visible as they would be using a serial dilution of the matrix only containing the same injected amount of the matrix. If you detect matrix interferences, you need to decide if they cause no significant effect to the measurement or change the method conditions (chromatography, detector, sample prep, etc.) to eliminate the interferences. Does any of this answer your question?

Thank you Russ. I think now I understand the concept.