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. 
direction to printer to disregard correction made to text, 1755, from Latin stet "let it stand," third person singular present subjunctive of stare "to stand, stand upright, be stiff," from PIE root *sta- "to stand, set down, make or be firm," with derivatives meaning "place or thing that is standing" (cf. Sanskrit tisthati "stands;" Avestan histaiti "to stand;" Persian -stan "country," literally "where one stands;" Greek histemi "put, place, cause to stand; weigh," stasis "a standing still," statos "placed," stater "a weight, coin," stylos "pillar;" Latin sistere "stand still, stop, make stand, place, produce in court," status "manner, position, condition, attitude," stare "to stand," statio "station, post;" Lithuanian stojus "place myself," statau "place;" Old Church Slavonic staja "place myself," stanu "position," staru "old," literally "long-standing;" Gothic standan , Old English standan "to stand," stede "place," steall "place where cattle are kept;" Old Norse steði "anvil," stallr "pedestal for idols, altar;" German Stall "stable;" Old Irish sessam "the act of standing"). Also see related words under assist .