A review on post-column derivatisation (PCD) using active flow technology (AFT) in reaction flow (RF) mode

Post column derivatisation reactions coupled with HPLC is a powerful tool available to chemists. This technique is useful in the analysis of a wide range of compounds that do not react strongly to any of the detectors available for modern HPLC analysis. We present a discussion of common post column derivatisation (PCD) reactions along with the chemical and instrumental setups required for analysis as well as advantages and disadvantages of certain techniques where more than one PCD technique is available for the derivatisation of a given molecule. After this, we introduce a new advancement in HPLC-PCD analysis, namely the active flow technology (AFT) column operated in reaction flow (RF) mode. PCD applications of AFT-RF have so far been limited to a small range of derivatisation techniques, however, it has shown advantages over traditional techniques such as increased sensitivity, theoretical plate counts and resolution. These increases in performance are due to less peak broadening due to the ability to reduce post column dead volume. It is anticipated that these advantages will be duplicated in any PCD reaction where the AFT-RF column is utilised. An additional advantage of AFT-RF over conventional PCD techniques is the ability to monitor the central, underivatised, reaction stream as well as the derivatised stream coming from the outer radial region of the AFT column, enabling multiplexed detection which can be used to extract extra information about the target molecule(s). The use of the AFT-RF column is a new technique that has the ability to improve the observed separation efficiency in a range of traditional PCD techniques.