Evaluation of the analyses of tert-butyldimethylsilyl derivatives of naphthenic acids by gas chromatography–electron impact mass spectrometry

Naphthenic acids are a complex mixture of carboxylic acids with the general formula CnH2n+ZO2 and they are natural, toxic components of crude oils. GC–MS analyses of tert-butyldimethylsilyl esters of naphthenic acids are used to estimate component distribution within naphthenic acids mixtures. Our evaluations of the GC–MS method showed that ions from column bleed erroneously appear as C14 Z = −4 acids and that correcting for heavy isotopes of C and Si do not significantly affect ion distribution plots. Overall, the GC–MS method appears to overestimate the relative proportion of low-molecular-mass acids.