In Chemical Analysis you simply calibrate your instruments against a known amount. That’s usually the control. Complex matrixes force you to perform a extraction before measuring and that obviously introduces noise. You can question the calibration, you can ask for increasing the sample size, but if a good chemical analysis laboratory tells you a result is consistently found on a product, I wouldn’t have much reasons to doubt it.
Yes, however most tobacco farmers have not switched to PGM mining, nor have the makers of Selsun Blue gilded their offices and homes in over-plentiful platinum.