ultrafiltration Filtration under pressure.

undercooling An uncommon method of biomolecular preservation in which emulsions are used to cool the solution below its freezing point without freezing.

underflow The dewatered solids that result from compaction during centrifugation.

unicellular A single-cell organism.

unit operation A distinct chemical or physical step in a downstream process, such as ultrafiltration, centrifugation, or chromatography.

UPLC® Technology The use of a high-efficiency LC system holistically designed by Waters Corporation to accommodate sub-2 μm particles and very high operating pressure is termed UltraPerformance Liquid Chromatography®. The major benefits of this technology are significant improvements in resolution over HPLC, and/or faster run times, while maintaining the resolution seen in an existing HPLC separation.

USP or USP-NF The United States Pharmacopeial Convention, Inc. establishes and disseminates officially recognized standards of quality and authoritative information for the use in the manufacture and testing of drugs, excipients, and raw materials. Also called one of the compendia. Other compendia include, for example, Ph.Eur (Pharmacopeia Europa), JP (Japanese Pharmacopeia). The USP, which defined specifications for approved drugs as well as general methods and guidances, merged with the NF, National Formulary, which focused on specifications for raw materials and excipients. General chapters are not legally binding, but specific chapters are considered to be binding, and defined USP methods are accepted by the FDA as an appropriate standard.

USP sterility test A method defined in the USP and Ph.Eur, and considered acceptable for per-lot testing of parenteral drugs to test for sterility. By itself, this test does not prove a given lot is sterile; rather, taken together with all other validation, GMP controls, and product/process testing, it increases confidence that a given lot is safe. (See sterility)

UV-vis Ultraviolet-visible spectroscopy; an analytical method that measures the absorption of light in the 200 to 750 nm range of the electromagnetic spectrum. It is used in determining protein concentration and is often applied to HPLC detection.