Basic Studies on Negative Ion Chemical Ionization Mass Spectrometry and Their Applications to Trace Analysis

Abstract

The basic studies on negative ion chemical ionization mass spectrometry (NCIMS) and their some applications to trace analysis are presented. In NCI of halogenated compounds by electron resonance capture reactions, the correlation between both NCIMS and GC-ECD responses, the ion species, the ion abundances and the ion abundance ratios (negative/positive), etc. were discussed. It was found the negative ion formation in NCI depended upon electron affinity and activation energy, and changes in their values produced about 10QQ-fold variation in ion formation. In NCI using C1 as a reactant ion, Cl could be easily generated from chloroform, and more stabilized by addition of methane. Moreover, the spectra obtained were useful to estimate the molecular weights of thermally labile compounds. The NCI spectra of polycyclic aromatic hydrocarbons, nitroarenes, and organochlorine compounds with methane and of dioxins with oxygen were evaluated for highly sensitive and/or selective detection. Alcohols, phenols, amines, carboxylic acids, and amino acids were derivatized with various fluorine-containing reagents to find the derivatives having high electron affinity and low activation energy. The NCI techniques developed 'were applied to detect or determine trace amounts of environmental pollutants or metabolites in human plasma.