Gradient chromatography is an elution mode in which a mobile-phase variable that controls retention is changed continuously or stepwise during a chromatographic run. The programmed variable is commonly organic-solvent fraction, ionic strength, or pH; its change alters solute distribution between mobile and stationary phases and causes compounds with different retention strengths to migrate within a practical time window [1]. Unlike isocratic chromatography, the mobile-phase elution strength is not constant. A gradient is characterized by its initial and final compositions, duration, shape, flow rate, and dwell volume between solvent mixing and the column inlet [2]. Peak compression occurs because the rear of a migrating band encounters a stronger mobile phase than its front, affecting peak width and separation performance [3]. The concept excludes flow programming without chemical change, temperature programming in gas chromatography, and nonchromatographic stepwise extraction. It is independent of the specific stationary-phase chemistry and can operate with reversed-phase, normal-phase, ion-exchange, or other retention mechanisms.
- gradient elution
- mobile-phase programming
- dwell volume
- peak compression
Chromatography in Natural Products • Analytical Chemistry • Chemistry • Physical Sciences
References
- L.R. Snyder; J.W. Dolan; J.R. Gant; Gradient elution in high-performance liquid chromatography. J. Chromatogr. A 1979, 165, 3-30, 10.1016/s0021-9673(00)85726-x.
- Pavel Jandera; Can the theory of gradient liquid chromatography be useful in solving practical problems?. J. Chromatogr. A 2006, 1126, 195-218, 10.1016/j.chroma.2006.04.094.
- Ken Broeckhoven; Gert Desmet; Theory of separation performance and peak width in gradient elution liquid chromatography: A tutorial. Anal. Chim. Acta 2022, 1218, 339962, 10.1016/j.aca.2022.339962.