A now that a blank is someting wituout the analyte...
You are right.
But we need a context to understand "fortified". I think there is some method of preparation this blank in your article, and word "fortified" just note special aspects of that blank....because when I read "blank" I think at something without the analyte but in this context doesn't have sense...i think
When it speaks about method validation , expecially for the accuracy of that method...it says :
"" a possible way to to measure the accuracy consists in using the results of a series of samples ( fortified blank) at differenct concentrations and then compare those with the expected values (calibration curve) ""
Don't know why it says fortified blank....never seen that term before in my studies....are these "fortified blanks" simply the standard solutions with note concentrations ?