derivatization
/ dih-RIV-uh-ty-ZAY-shun /
Derivatization is chemically dressing up a molecule that an instrument struggles to see, by attaching a small chemical tag that makes it easier to detect or to move through the apparatus. Imagine a person who is hard to spot in a crowd; pin a bright badge on them and suddenly they stand out — derivatization pins a chemical badge on the analyte for the same reason.
Concretely, the analyte is reacted with a chosen reagent to form a new compound — a derivative — that behaves better in the method. The tag might add colour or fluorescence so a detector can see the molecule, make a stubborn, non-volatile compound volatile enough to travel through a gas chromatograph, or improve how cleanly it separates from its neighbours.
It is a powerful way to bring otherwise invisible or uncooperative analytes within reach of a technique. The caveats are real: the reaction must go essentially to completion and reproducibly, or it adds its own error; it introduces extra reagents, time, and possible contamination; and the derivative must be stable long enough to measure.
Amino acids carry no useful colour, so before HPLC the analyst reacts them with a fluorescent tag; each tagged amino acid now glows under the detector and shows up as a clear peak.
A chemical tag makes an invisible analyte stand out to the detector.
Derivatization can be done before the separation (pre-column) or after it (post-column). Pre-column gives more freedom in choosing the reagent but the derivative must itself survive the separation; post-column tags everything right before detection, with no time to drift but at the cost of extra plumbing.