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. 
-Solution, ointment, gel, foam, cream formulations: Apply a thin layer to affected areas twice a day and rub in gently and completely. Not recommended for use in children under 12 years of age.
-Shampoo, spray, and lotion formulations: Not recommended for use in children under 18 years of age.
Maximum dose: The total dosage should not exceed 50 g (50 mL or fl. oz.) per week.
Duration of therapy: Treatment should be limited to 2 consecutive weeks for the relief of the inflammatory and pruritic manifestations of corticosteroid-responsive dermatoses and up to 2 additional weeks in localized lesions (less than 10% body surface area) of moderate to severe plaque psoriasis that
have not improved after the initial 2 weeks of treatment.
Comments: Unless directed by a healthcare professional, this drug should not be used with occlusive dressings.
-Corticosteroid-responsive inflammatory and pruritic dermatoses; psoriasis; recalcitrant eczemas, lichen planus, discoid lupus erythematosus, and other conditions which do not respond satisfactorily to less active steroids.