In chemistry, residue is the material remaining after distillation or an evaporation, or to a portion of a larger molecule, such as a methyl group. It may also refer to the undesired byproducts of a reaction. Residues are important in chemistry, where distillation products are quantitatively analyzed. During the distillation of white wine, after ethanol has been extracted, water and sugar are the main ingredients of the residue. In this case, the residue is not undesired product. The residues are tested for ethanol for the conclusiveness of the distillation.
The effects of chemical kinetics on residue curve maps for reactive distillation is currently studied at University of Massachusetts. Reactive distillation is not always advantageous, so there is a need for systematic methods to decide when this technique should be used. The kinetics of residue formation can inform methods in its removal.
Also, studies of chemical residues have huge implications on food toxicity. According to the Canadian Food Inspection Agency, food supply is probed for chemical contamination caused by chemical residue. In 2012, a total of 628 samples were collected and analyzed in dried food category (figs, dried dates, corn products, and nut products). Samples were analyzed for residues using a multi-residue method that detects the Aflatoxins forms B1, B2, G1 and G2. Both the levels of the individual forms and the total aflatoxin levels were reported. Most of the samples (584/628 or 93%) did not contain detectable levels of AF. In another food category, residue seems to be causing a lot of toxins. In 2011, a total of 288 bottled water samples (spring, mineral, and purified water, both domestic and imported) were randomly selected and tested of bromate residue. Bromate can form in bottled water when bromide is present in water during disinfection via zonation. Bromide ions are naturally occurring compounds in water resulting from runoff, leaching, or seawater intrusion, and is potentially carcinogenic. Toxic chemical residues are a concern in food safety. The FDA has guidelines for detecting chemical residues that are possibly dangerous to consume.
In biochemistry and molecular biology, a residue refers to a specific monomer within the polymeric chain of a polysaccharide, protein or nucleic acid. One might say, "This protein consists of 118 amino acid residues" or "The histidine residue is considered to be basic due to its imidazole ring." Note that a residue is different from a moiety, which, in the above example would be constituted by the imidazole ring or "the imidazole moiety".
During the process by which monomeric building blocks (e.g. amino acids) are strung together into a polymeric chain (e.g. a protein), some material (typically adding up to one molecule of water) is discarded from each building block, and only a "residue" of the building block ends up in the finished product. A residue may be one amino acid in a polypeptide.
"Drug & Chemical Residues Methods." FDA.gov. US. Food and Drug Administration, Apr.-May 2005. Web. Apr.-May 2013. <www.fda.gov>.
"Bromate in Bottled Water." Canadian Food Inspection Agency. N.p., Feb.-Mar. 2007. Web. 18 Apr. 2013. <http://www.inspection.gc.ca/>.
"2010-2011 Aflatoxins in Dried Fruits, Nuts and Nut Products, and Corn Products." Canadian Food Inspection Agency. N.p., Aug.-Sept. 2009. Web. 18 Apr. 2013. <http://www.inspection.gc.ca/>.
Baker, Lane. Exp-11 Kinetics of the Iodine Clock Reaction (pp. 1–12). Experimental Procedures / Appendices.