High-pressure liquid chromatography derivatisation

Apart from the above reasons derivatisation is also required in the analyses of many of the newer pesticides which have one or more functional groups which need protection in order to facilitate GC work. Also the increased use of high pressure liquid chromatography (HPLC) necessitates pre- or post-column derivatisation since the choice of HPLC detectors is limited compared with GC. 

Derivatives may also be used to m e the molecule capable of detection by selective detectors. The reaction may be carried out during extraction (e.g. extractive methylation), on the dry residue (e.g. silylation), or during injection (e.g. methylation). If a compound requires derivatisation in order to reduce its polarity, the use of high pressure liquid chromatography should be considered instead of GLC, assmning that sensitivity is not the limiting factor. 

Quantification. High Pressure Liquid Chromatography. In serum erythromycin and erythromycin ethylsuccinate, detection limits < 10 ng/ml, derivatisation and fluorescence detection—K. Tsuji, J. Chromat., 1978,158, 337-348. 

In spite of the excellent separation of anthraquinones by GLC, one preferably uses high pressure liquid chromatography (HPLC) for the separation of these compounds. For an HPLC separation the anthraquinones do not have to be silylated, which saves time and prevents possible losses during the derivatisation. 

Advances in stationary phase technology have led to commercial availability of adsorbents such as high performance sihcas, aluminas, polyamides, celluloses and derivatised silicas [9,10], The development of automated method development (AMD) systems [127] now allow multi-step gradients of different elution strengths to be achieved in a relatively short time compared to earlier manual approaches. AMD systems are ideally suited for separation of complex mixtures with a wide range of polarities. Further improvements in sample resolution and reduced method development times in TLC include the use of two-dimensional development approaches [128] and forced-flow development by over-pressure liquid chromatography (OPLC) [129]. 

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