Comprehensive Two-Dimensional Gas Chromatography with Peak Tracking for Screening of Constituent Biodegradation in Petroleum UVCB Substances

Petroleum substances,
as archetypical UVCBs (substances of unknown
or variable composition, complex reaction products, or biological
substances), pose a challenge for chemical risk assessment as they
contain hundreds to thousands of individual constituents. It is particularly
challenging to determine the biodegradability of petroleum substances
since each constituent behaves differently. Testing the whole substance
provides an average biodegradation, but it would be effectively impossible
to obtain all constituents and test them individually. To overcome
this challenge, comprehensive two-dimensional gas chromatography (GC
× GC) in combination with advanced data-handling algorithms was
applied to track and calculate degradation half-times (DT50s) of individual constituents in two dispersed middle distillate
gas oils in seawater. By tracking >1000 peaks (representing ∼53–54%
of the total mass across the entire chromatographic area), known biodegradation
patterns of oil constituents were confirmed and extended to include
many hundreds not currently investigated by traditional one-dimensional
GC methods. Approximately 95% of the total tracked peak mass biodegraded
after 64 days. By tracking the microbial community evolution, a correlation
between the presence of functional microbial communities and the observed
progression of DT50s between chemical classes was demonstrated.
This approach could be used to screen the persistence of GC ×
GC-amenable constituents of petroleum substance UVCBs.