eluetappen

Eluetappen is a term used in chromatography to describe the discrete stages of the elution part of a separation. In chromatographic methods, a sample is applied to a column containing a stationary phase and a mobile phase flows through it. The interaction between analytes and the stationary phase determines their retention times, and elution steps are used to modulate this process by altering the mobile phase conditions.

Eluetappen correspond to defined changes in the elution program. In isocratic elution, the mobile phase composition remains constant, effectively making the process a single step. In gradient elution, the composition, and sometimes other parameters such as pH, ionic strength, flow rate, or temperature, are changed in a sequence of steps. Each step represents a stage where a new eluting strength is applied, helping to elute compounds with different retention characteristics and improving peak separation.

The purpose of planning eluetappen is to optimize separation efficiency, resolution, run time, and peak shape. In analytical chromatography, steps are chosen to separate components sufficiently before detection, while in preparative chromatography they facilitate the collection of fractions enriched in target compounds. Automation in modern systems allows programmable stepwise or continuous gradient elution, enabling precise control over the elution profile.

Terminology varies by language; in German-language literature, eluetappen specifically denotes these programmed steps within an elution protocol. The concept is central to many chromatography techniques, including reversed-phase, normal-phase, ion-exchange, and size-exclusion systems.