detection limit - amount of sample which produces a signal twice the noise level.

See also noise and drift.

detector - part of the chromatograph which constantly monitors the composition of the column effluent by measuring some physical property of the eluent and eluted compounds.

See HPLC detectors.

detector cell (flow cell) - part of the HPLC detector where actual measurement of effluent physical properties occurred. Cell volume is usually from 1 to 10 µl.

See HPLC flow cell.

diaphragm pump - a reciprocating piston pump which acts not directly on the mobile phase, but on hydraulic fluid in a closed system. The pumped hydraulic fluid compresses a flexible steel diaphragm, which in turn pumps mobile phase with a reaction in flow stream pressure pulsation

displacement - a form of chromatography (like elution and frontal) where stronger solvents are used in series to displace (desorb) sample components; used occasionally in liquid chromatography.