Analysis of amino acids and organometallic compounds by particle beam-hollow cathode glow discharge atomic emission spectrometry

An evaluation of the particle beam-hollow cathode glow discharge atomic emission spectroscopy (PB-HC-AES) system as an element-specific detector for liquid chromatography is described for aromatic amino acids and organomercury and organolead compounds. A high-efficiency thermoconcentric nebulizer is used to introduce analyte particles into a heated hollow cathode glow discharge source for subsequent vaporization, atomization and excitation. Emission responses for hydrogen and nitrogen of amino acids in flow injection mode using 200 mu L injection volumes indicate detection limits of 0.13 and 3.6 ppm elemental H and N, respectively, with RSD < 10% for triplicate injections over a concentration range of 10(-3)-10(-2) M. Analysis of the response of hydrogen and nitrogen emission signal intensities to differences in amino acid stoichiometries indicates the potential of the PB-HC-AES system for the determination of empirical formulas based on H I/N I intensity ratios. Detection limits for metals and non-metals in organomercury compounds as determined through flow injection of 200 mu L sample volumes fall in the sub-ppm range. Liquid chromatographic separations of both amino acids and organolead compounds demonstrate the feasibility of the PB-HC-AES system as a detector for liquid chromatography. Retention times for 20 mu L injections of the selected component mixtures as determined by C I emission for amino acids and Pb I emission for organolead compounds correlate well with the corresponding UV absorbance results.