What is the graph? Can you post a picture?
mAU*min sounds like the area of a chromatography peak. If you have a calibration curve (compound-specific and instrument-specific) of mAU*min vs. moles injected, you can work out how many moles of sample were injected (and, with the injection volume, the concentration).
The activity A of a sample in Becqerel is given by A = nNA*ln2/t1/2
where n is the number of moles, NA the Avogadro constant, and t1/2 the half-life in seconds.
The specific activity would be A/m (per gram) or A/n (per mole).
If your sample mass is m g, and your injection contained mi g, and the peak area indicates ni moles in the injection, then your sample contains n = ni*m/mi moles of compound.