Chemiluminescence detection of amino acids using an Edman-type reagent, 4-(1′-cyanoisoindolyl)phenylisothiocyanate

The 4-(1′-cyanoisoindolyl)phenylisothiocyanate (CIPIC) could be used as a chemiluminescence (CL) Edman-type reagent. Firstly, CL reaction conditions such as pH, buffer types, H2O2 concentration and organic solvents were optimized in detail. Secondly, the CL sensitivity of the derivative of Ala was compared with fluorescence and absorbance detections. Thirdly, the structures of the CL intermediate and emitter were elucidated by liquid chromatography-mass spectrometry (LC-MS) and NMR of CIPIC and its analogues after their CL reactions. Consequently, the thiohydantoin derivatives for 16 kinds of amino acids were separated and sensitively detected by CL with lower detection limits of 0.3-0.8 pmol at a signal-to-noise ratio of 3, after the coupling reaction of amino acids with CIPIC and their cyclisation reaction.