@janoshik question, is mcg doses harder to get in closer standard deviation regardless if Pharmaceutical or Ugl?
There is too many variables with each and every compound, really.
Varies with lab equip (eg. triple quad mass spec is great for looking for picograms, but it will always be less precise and accurate than simple UV, which however is not as sensitive). Varies with compound (some ionizable shits like to adhere to stainless steel tubing or even vial glass!). Varies with sensitivity of the compound (2,4 DNP eg. is even used as a default example of an extremely sensitive compound in GC)...
Generally, if you have compound that has issues with being sensitive or adheres to something, having high concentration sample is always better than low concentration. Eg. if you analyze 3.33 mg of HGH, then you don't have to care much about 0.0005 mg of it adhering to glass vials and stainless steel of tubing. However, if you analyzed 0.001 mg of HGH, you'd better use plastics instead or your results will be skewed big time.
Clen is a non-issue compound, I believe I have very good method for it.
Biggest issue with clen is that you have to wait months for standards, lol.
I hope I made that understandable, I've had a few beers.
Cheers