Evaporators are designed to remove aqueous or volatile liquid from samples, leaving desired analyte material intact. Instruments can include rotary evaporators (rotovaps), centrifugal evaporators, blow-down units, and others. Important considerations include the power and performance of the vacuum system, the heating (or cooling) components, and the integrity of the unit in general. Concentrators can be classified as above and also include circulating units designed to remove excess liquid and concentrate solutions. Examples include tangential or cross flow concentrators, either disposable or reusable. Considerations include ease of setup and breakdown, performance, and flexibility in filter or membrane use and exchange.