Automated pre-column derivatization and its application to amino-acid analysis using high-performance liquid chromatography

Although chemical modification of analytes is a well-accepted adjunct to chromatography, little attention had been paid to the automation of pre-column derivatization techniques. An automated pre-column system would offer advantages when analyses are performed using labile derivatives; and also when the time between injections is long and so staff time spent on achieving maximum analytical output is less than optimal. Both of these features exist with the analysis of amino-acids in physiological samples using pre-column 0-phthalaldehyde! 2-mercaptoethanol (OPA/MCE) derivatization and reversedphase high-performance liquid chromatography (HPLC) [1]. These fluorescent derivatives are labile !-1 and 2-1 and therefore have to be prepared in a precise manner immediately before injection onto the column. A system is described for automatically sampling, derivatizing and injecting specimens onto an HPLC and analysing for amino-acids. Furthermore, this system may be operated overnightmcapitalizing on the reduced chromatographic run time when compared with amino-acid analysis using ionexchange post-column derivatization methods [3].