you'd be able to find the concentration if you knew the pH of the solution, and the Ka of LSD. But all I can find is someone says the ph is "about 4" which isn't particularly helpful, because the conc. wasn't stated.
I'm still looking though.
edit, apparently pka(lsd)=7.8
[lsd] =(10^-pH)^2/ 10^-7.8
which would give conc. in mol/litre
then get mass from molar mass.
This assumes the liquid is pure water, and is likely to turn out totally wrong
edit2: so for 100ug/ml, the pH would be 5.65