4. End-of-fixing volume

4.1 Definition

In trace analysis, the loss of a compound during the preconcentration stage is often due to insufficient retention of the solute eluted by the sample solvent, such as water for aqueous samples. This end-of-fixation volume V _f , from which the solute is eluted, is therefore linked to the solute's affinity for the adsorbent. To explain how to measure or estimate its value, the extraction of a compound from an aqueous sample is used as an example. This example can then be transposed to any other type of sample, taking into account the nature of the solvent used.