Residue (chemistry)

Inchemistry,residueis whatever remains or acts as acontaminantafter a given class of events. Residue may be the material remaining after a process of preparation, separation, or purification, such asdistillation,evaporation,orfiltration.It may also denote the undesiredby-productsof achemical reaction.

Distillation apparatus

Residues as an undesired by-product are a concern in agricultural and food industries.

Food safety

Toxic chemical residues, wastes or contamination from other processes, are a concern in food safety. The most common food residues originate from pesticides, veterinary drugs, and industrial chemicals.For example, the U.S.Food and Drug Administration(FDA) and theCanadian Food Inspection Agency(CFIA) have guidelines for detecting chemical residues that are possibly dangerous to consume.In the U.S., the FDA is responsible for setting guidelines while other organizations enforce them.

Environmental concerns

Similar to the food industry, in environmental sciences residue also refers to chemical contaminants. Residues in the environment are often the result of industrial processes, such as escaped chemicals fromminingprocessing, fuel leaks during industrial transportation, trace amounts ofradioactivematerial, and excess pesticides that enter the soil.

3D image of Aflatoxin

Characteristic units within a molecule

Residue may refer to anatomor a group of atoms that form part of amolecule,such as amethyl group.

Biochemistry

Inbiochemistryandmolecular biology,a residue refers to a specificmonomerwithin thepolymeric chainof apolysaccharide,proteinornucleic acid.

In proteins, the carboxyl group of one amino acid links with the amino group of another amino acid to form a peptide. This results in the removal of water and what remains is called the residue. Naming of residues is done by replacing "acid" with "residue".A residue's properties will influence interactions with other residues and the overall chemical properties of the protein it resides in. One might say, "Thisproteinconsists of 118amino acidresidues "or" Thehistidineresidue is considered to be basic because it contains animidazolering. "Note that a residue is different from amoiety,which, in the above example would be constituted by theimidazole ringor theimidazole moiety.