On-capillary derivatisation as an approach to enhancing sensitivity in capillary electrophoresis

Separation technologies play an important role in revealing biological processes at various omic levels, in pharmacological and clinical research. In this context, CE is a strong candidate for analyses of samples with rapidly increasing complexity. Even though CE is well known for its many advantages in this regard, the sensitivity of CE analyses is insufficient for many applications. Accordingly, there are generally three main options for enhancing the sensitivity of CE analyses - using special detection techniques, using sample pre-concentration and derivatisation. Derivatisation is often the method of choice for many laboratories, since it is simple and provides several advantages such as small sample volume demand and the possibility of automation. Although it can be performed in different ways depending on where the reaction takes place, this article reviews one of the simplest and at the same time most useful approaches on-capillary derivatisation. Even if in many cases the use of on-capillary derivatisation alone is enough to improve the detection sensitivity, on other occasions it needs to be employed in combination with the other above-mentioned strategies. After a simple discussion of derivatisation in general, special attention is focused on the on-capillary approach and methodologies available for on-capillary reactant mixing. Its applications in various fields are also described.