Simultaneous determination of multiple aldehydes in biological tissues and fluids using gas chromatography/stable isotope dilution mass spectrometry.

Biological oxidative stress has been associated with various degenerative disorders and disease states, and accurate and sensitive methods are needed to determine the extent of oxidation occurring in vivo. Peroxidation of polyunsaturated fatty acids forms complex mixtures of aldehydes and other breakdown products because various oxidants are involved and lipid composition is not uniform. Quantitative analysis of multiple lipid peroxidation products yields a more complete measure of biological oxidation than measurement of a single aldehyde, particularly when aldehydes exhibit marked differences in reactivity. This report describes extensions of an established gas chromatography/mass spectrometry method to include stable isotope dilution determination in tissue and plasma of three aldehydic products of lipid peroxidation: hexanal, nonanal, and 4-hydroxy-2-nonenal. Use of deuterated internal standards for each analyte improved precision and accuracy compared to a single internal standard for all three aldehydes. Improvements are attributed to differences in extraction and derivatization efficiencies for individual analytes owing to substantial differences in reactivity. Electron ionization of oxime-tert-butyldimethylsilyl derivatives gave greater specificity for detecting all three aldehydes than was possible using electron-capture ionization of O-pentafluorobenzyl oxime derivatives. Exchange of the deuterium label of [2,3-2H]HNE internal standard was determined to be minimal during the analyses.