Steroid isolation , depending on context, is the isolation of chemical matter required for chemical structure elucidation, derivitzation or degradation chemistry, biological testing, and other research needs (generally milligrams to grams, but often more  or the isolation of "analytical quantities" of the substance of interest (where the focus is on identifying and quantifying the substance (for example, in biological tissue or fluid). The amount isolated depends on the analytical method, but is generally less than one microgram.  [ page needed ] The methods of isolation to achieve the two scales of product are distinct, but include extraction , precipitation, adsorption , chromatography , and crystallization . In both cases, the isolated substance is purified to chemical homogeneity; combined separation and analytical methods, such as LC-MS , are chosen to be "orthogonal"—achieving their separations based on distinct modes of interaction between substance and isolating matrix—to detect a single species in the pure sample. Structure determination refers to the methods to determine the chemical structure of an isolated pure steroid, using an evolving array of chemical and physical methods which have included NMR and small-molecule crystallography .  :10–19 Methods of analysis overlap both of the above areas, emphasizing analytical methods to determining if a steroid is present in a mixture and determining its quantity. 
Many advanced users stack several compounds in order to get maximum results from their cycle. Normally when your stacking these types of supplements its best to use single compounds instead of premixed stacks. The problem with using a premixed stack is you may get more of one compound than you want. Most of these products have sweet spots. Lets use h-drol for an example according to many of the forums out there 75mg is the sweet spot for this compound. Now lets say you have a halodrol product that is mixed with 10mg of Methylstenbolone. In order to get the proper amound of hdrol you will get more than the recommended dose of M-sten.