Hold on a sec while I get some popcorn going.

You don't do HPLC without doing mass spec first. I mean you probably could but you don't. Mass spec will give you the molecular weight of whatever drug you put into the machine. Say you want to asses the purity of what you think is testosteone. It has a molecular weight of 288.42g/mol. Say your sample comes up nowhere close to that. Then you know you don't have testosterone and there's no reason to do HPLC on it. If it does come up with the right molecular weight it still doesn't mean you have testosterone but you can be pretty damn sure if your sample is supposed to be test and it comes back with the right weight then you probably have testosterone. So then the next step is to run it through the HPLC machine which will give you the purity, all the impurities, the concentration (mg/ml). You just have to send it to a reliable lab where the guys doijg the test know how to interpret them correctly. Problems with MS/HPLC isn't the machines falt assuming it's calibrated correctly, it's usually human error