Accelerated benzene polycarboxylic acid analysis by liquid chromatography-time-of-flight-mass spectrometry for the determination of petrogenic and pyrogenic carbon

Hindersmann B, Achten C

Abstract

Pyrogenic carbon species are of particular interest due to their ubiquitous occurrence in the environmentand their high sorption capacities for nonpolar organic compounds. It has recently been shown that theanalysis of the molecular markers for complex aromatic carbon structures, benzene polycarboxylic acids(BPCA), has a high potential for aid in the identification of different carbon sources.In this study, the first LC method using mass spectrometry (MS) for reliable and accelerated (<24 h)quantification of pyrogenic and petrogenic carbon by BPCA analysis has been developed. The mainadvantage of LC–MS compared to previous methods is the higher sensitivity, which is important if onlysmall sample amounts are available. Sample pre-treatment could be reduced to a minimum. Deuteratedphthalic acid was introduced as internal standard due to its structural similarity to BPCA and its lackof occurrence in the environment. Linear quantification with r2≥ 0997 was accomplished for all BPCA.Method validation showed an excellent quantification reproducibility (mean CV < 5%) which is compa-rable to LC-DAD methods and more reliable than GC-FID measurements (CV 16–23%). In summary, thepresented BPCA method is more economic, efficient and presumably attractive to use.Besides reference materials, various pyrogenic and petrogenic samples were analyzed to test if thesources were indicated by BPCA analysis. In addition to pyrogenic carbon, large amounts of petrogeniccarbon species can also be present in urban soils and river sediments, especially in mining regions. Theyalso to a large degree consist of aromatic carbon structures and therefore have an impact on source iden-tification by BPCA analysis. Comparison of petrogenic and pyrogenic carbon samples shows similarities inthe BPCA concentrations and patterns, in their aromaticity and degree of aromatic condensation. Thus, adifferentiation between petrogenic and pyrogenic carbon only by BPCA analysis of samples with unknowncarbon sources is not possible. For reliable source identification of the carbon species, the combinationwith other methods, such as e. g. analysis of polycyclic aromatic hydrocarbons may be successful.