Editing Steroid (section)

== Isolation, structure determination, and methods of analysis ==

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<ref name="Landmark_ACS"/> 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.<ref name = "Makin_Gower_2010">{{cite book | veditors = Makin HL, Gower DB | title = Steroid analysis | vauthors = Makin HL, Honor JW, Shackleton CH, Griffiths WJ | chapter = General methods for the extraction, purification, and measurement of steroids by chromatography and mass spectrometry | pages = 163–282 | date = 2010 | publisher = Springer | location = Dordrecht; New York | isbn = 978-1-4020-9774-4}}</ref>{{page needed|date=May 2014}}

The methods of isolation to achieve the two scales of product are distinct, but include [[extraction (chemistry)|extraction]], precipitation, [[adsorption]], [[chromatography]], and [[crystallization]]. In both cases, the isolated substance is purified to chemical homogeneity; combined separation and analytical methods, such as [[Liquid chromatography–mass spectrometry|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]].<ref name = "Lednicer_2011"/>{{rp|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.<ref name = "Makin_Gower_2010"/>