High Sensitivity Fluorescence Detection of Naphthalenedialdehyde- Derivatized Amino Acids with a Low Power Helium-Cadmium Laser for High Performance Liquid Chromatographic Analysis

The development of a convenient, low cost, low power He-Cd laser-induced fluorescence (LIF) detection system for HPLC is described. The system was developed for the detection of primary amines derivatized with naphthalenedialdehyde (NDA). The LIF system incorporates a fiber optic cell similar to the cell developed by Yeung and coworkers, which was modified in order to improve the S/Nratio. The LIF system exhibited detection limits of 0.75-1.2fmol which was comparable to the detection limits obtained for the derivatized amino acids with a high power argon ion LIF system and demonstrated a tenfold improvement in comparison to a commercial fluorescence detector. In addition, the LIF cell, collection optics and photomultiplier tube were mounted on a standard laboratory ringstand, which allowed the system to be easily moved. The applicability of the LIF system was demonstrated by derivatizing a human tear sample with NDA and subjecting it to HPLC analysis with LIF detection. Several amino acids were identified in the resulting chromatogram.