Ortho-phthaldialdehyde

Certainly, a vast amount of experience has been gained by the widespread use of conventional amino acid analysers. They offer high reliability, accuracy, reproducibility and can separate complex samples. Because conventional analysers can be fully automated, they are widely used in routine analysis. However, the method is limited by the sensitivity which can be achieved using ninhydrin as the derivatizing agent. Sensitivity can be increased by using ortho-phthaldialdehyde (OPA) instead, but where extremely high sensitivity is required, HPLC is the method of choice. 

Pentoney, S. L., Huang, X. H., Burgi, D. S., and Zare, R. N., Online connector for microcolumns— Application to the on-column ortho-phthaldialdehyde derivatization of amino-acids separated by capillary zone electrophoresis. Anal. Chem., 60, 2625, 1988. 

Rose, D. J. and Jorgenson, J. W., Post-capillary fluorescence detection in capillary zone electrophoresis using ortho-phthaldialdehyde, J. Chromatogr., 447,117,1988. 

Figure 43 Derivatisation of baclofen with ortho-phthaldialdehyde/t-butylthiol under alkaline conditions. ...

The various peptides and proteins have been located on the thin layer chromatograms by using ninhydrin, fluorescamine, ortho- phthaldialdehyde, iodine vapors or UV the quantitation has been performed by densitomelric scanning or by spectrophotometry after eluting the peptides immuno-chromatography using monoclonal antibodies has also been used for quantification. 

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