Mass Spectral Characterization of p-Nonylphenol Isomers Using High-Resolution Capillary GC--MS

High-resolution gas chromatographic (GC) analyses of p-nonylphenol at selected oven temperatures have achieved resolution of 22 para-isomers. Separation is accomplished through the use of a 100-m capillary GC column exhibiting over 400,000 theoretical plates. Coupling this GC analysis to a mass spectrometer has resulted in discrete mass spectra that more accurately characterize this important group of isomers. Analysis of the spectra indicates the presence of five distinct groups of isomers. Group designations are presented based on the substitution of the alpha-carbon on the alkyl chain. This data, in conjunction with model mass spectra, elucidate the structures of p-nonylphenol isomers. Quantitative analysis using high-resolution GC with a flame-ionization detector is also presented. Fourier transform infrared analysis confirms ortho- and para-phenolic substitution. Examination of the infrared fingerprint region provides an unequivocal confirmation of phenolic substitution.