Measurement of total and free malondialdehyde by gas-chromatography mass spectrometry--comparison with...

Malondialdehyde (MDA) is considered to be a biomarker for enzymatic degradation and lipid peroxidation of polyunsaturated fatty acids. Usually, MDA determination from different biological materials is performed by reaction with thiobarbituric acid (TBA) followed by high-performance liquid chromatography (HPLC) analysis and fluorometric detection. As this method lacks specificity and sensitivity, we developed a gas chromatography-mass spectrometry (GC-MS) method based on derivatization of MDA with 2,4-dinitrophenylhydrazine. Representative ions in negative ion chemical ionization (NICI) mode were recorded at m/z 204 for MDA and at m/z 206 for the deuterated analogon (MDA-d₂) as internal standard. This stable and precise GC-MS method showed good linearity (r² = 0.999) and higher specificity and sensitivity than the HPLC method and was validated for both total MDA (t-MDA) and free MDA (f-MDA). Within-day precisions were 1.8-5.4%, between-day precisions were 4.8-9.2%; and accuracies were between 99% and 101% for the whole calibration range (0.156-5.0 μmol/L for t-MDA and 0.039-0.625 μmol/L for f-MDA). Although comparison of t-MDA levels from GC-MS and HPLC results using Passing-Bablok regression analysis as well as Bland-Altman plot showed a correlation of the data, a tendency to increased results for the HPLC values was detectable, due to possible formation of unspecific products of the TBA reaction.