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. 
Nonsteroidal anti-inflammatory drugs (NSAIDs) can affect renal function in a variety of ways. The most important clinical effects are decreased sodium excretion, decreased potassium excretion, and declines in renal perfusion. Decreased sodium excretion can result in weight gain, peripheral edema, attenuation of the effects of antihypertensive agents, and rarely precipitation of chronic heart failure. Hyperkalemia can occur to a degree sufficient to cause cardiac arrhythmias. Renal function can decline sufficiently enough to cause acute renal failure. Risk factors for all of these effects have been identified, allowing prospective identification of patients at risk with institution of appropriate precautionary measure. All NSAIDs seem to share these adverse effects. Preliminary data from cyclooxygenase-2-selective inhibitors suggest that they also affect renal prostaglandins. Therefore, the same cautions should be exercised with their use as with traditional NSAIDs.