eluent The substance used to recover samples from a chromatography column; sometimes an elution solvent. When a buffering agent is used, it is called an elution buffer. Sometimes a solvent is used and just referred to as the eluent.

Electrospray ionization is used to transfer analytes from liquid to a gaseous phase in an ionized form.

elution profile A graph made to show how much material is being carried out of the column by the eluent in column chromatography over time. The graph will show a number of different peaks; each peak represents a different separated material from the original mixed substance. Also called a chromatogram.

EM Electron microscopy; in which instruments focus electrons like optical microscopes focus light. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) are sometimes used in bioanalytical laboratories.

EMEA European Medicines Evaluation Agency; the agency responsible for regulating biopharmaceuticals in the European Union.

emulsification A process that creates a stable mixture of two liquids that normally would not mix together (such as oil and water) by forcing one to disperse in the other as droplets.

enantiomer Either of a pair of chemical compounds whose molecular structures have a mirror-image relationship to each other (see diastereomer).

encapsidation During formation of a virus particle, the process by which nucleic acid is incorporated (encapsidated) into the viral capsid. (See also capsid)

encapsulation To enclose in a capsule, usually one made of a biodegradable polymer.

endogenous Growing or developing from a cell or organism, or arising from causes within the organism.

endonuclease A restriction enzyme that breaks up nucleic acid molecules at specific sites along their length. Such enzymes are naturally produced by microorganisms as a defense against foreign nucleic acids.

endoplasmic reticulum A highly specialized and complex network of branching, interconnecting tubules (surrounded by membranes) found in the cytoplasm of most animal and plant cells. The rough endoplasmic reticulum is where ribosomes make proteins. It appears "rough" because it is covered with ribosomes. The smooth endoplasmic reticulum is the site for synthesis and metabolism of lip-ids, and it is involved in detoxifying chemicals such as drugs and pesticides.

endotoxin A poison in the form of a fat/sugar complex (lipopolysaccharide) that forms a part of the cell wall of some types of bacteria. It is released only when the cell is ruptured and can cause septic shock and tissue damage. Pharmaceuticals are tested routinely for endotoxins.

engineering batch A batch run at the defined cGMP production scale for the purpose of evaluating the performance of any or all of the unit operations prior to initiating cGMP manufacturing. It is not intended to be released as a fully compliant cGMP batch. An engineering batch may be executed using a batch record, but need not comply with all instructions and requirements.

enthalpy Heat content; enthalpy change of a chemical reaction equals the difference between the heat put into breaking bonds and the heat released by new bond formation.

environmental monitoring A documented series of sampling and testing performed on controlled environments to assure compliance with room classifications. Testing typically includes monitoring of viables and non-viables via standardized sampling methods performed at established time intervals.

enzymes Proteins that catalyze biochemical reactions by causing or speeding up reactions without being changed in the process themselves.

epithelium (epithelial) The layer(s) of cells between an organism or its tissues or organs and their surrounding environment (skin cells, inner linings of lungs or digestive organs, outer linings of kidneys, and so on).