User:HighQualityWater/Residue (chemistry)

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Within the sciences residue is a complex concept with multiple meanings. The general definition for residue is a product left behind after a chemical reaction, and can refer to the main product, a by-product, or a combination of both.

In chemistry, residue is what remains or acts as a contaminant after a given class of events. Residue may be the material remaining after a process of preparation, separation, or purification, such as distillation, evaporation, or filtration. It may also denote the undesired by-products of a chemical reaction.

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. The U.S. Food and Drug Administration (FDA) and the Canadian 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 from mining processing, fuel leaks during industrial transportation, trace amounts of radioactive material, and excess pesticides that enter the soil.

Chemistry and Other Fields
Residue may refer to an atom or a group of atoms that forms part of a molecule, such as a methyl group.

In biochemistry and molecular biology, a residue refers to a specific monomer within the polymeric chain of a polysaccharide, protein or nucleic acid. In proteins, the amino acid monomer is a unique residue with unique properties. A residue's properties will influence interactions with other residues and the overall chemical properties of the protein it resides in. Note that a residue is different from a moiety.