A gradient, starting with hexane (0.1 min) and reaching 30% of
dichloromethane (at 300 lL/min) in 0.5 min, was used to elute
the MOSH (from 2.0 to 3.5 min) and the MOAH (from 4 to
5.5 min) as described by Biedermann et al. (2009).
LC–GC transfer occurred through the Y-interface based on the
retention gap technique and partially concurrent eluent evaporation.
A 10 m 0.53 mm i.d. uncoated, deactivated precolumn was
connected by a steel T-piece union to the solvent vapour exit
(SVE) and a 15 m 0.25 mm i.d. separation column coated with
a 0.15 lm film of PS-255 (1% vinyl, 99% methylpolysiloxane)
(Mega, Legnano, Italy). A rapid oven gradient (40 C min1) starting
from 55 up to 350 C was used for GC analysis (Barp et al., 2013).
The FID and the SVE were heated at 360 and 140 C, respectively.
After the transfer, the LC column was backflushed (dichloromethane)
and reconditioned prior to the subsequent injection.
The data were acquired and processed by ExaChrom software
(Brechbühler, Switzerland). The MOSH area was determined by
the integration of the whole hump of largely unresolved peaks,
subtracted from the endogenous n-alkanes. All sharp peaks standing
at the top of the MOAH hump were subtracted from the total
area. Quantification was based on internal standards or on external
standard, when the presence of sample components co-eluting
with the standards was suspected.
A gradient, starting with hexane (0.1 min) and reaching 30% ofdichloromethane (at 300 lL/min) in 0.5 min, was used to elutethe MOSH (from 2.0 to 3.5 min) and the MOAH (from 4 to5.5 min) as described by Biedermann et al. (2009).LC–GC transfer occurred through the Y-interface based on theretention gap technique and partially concurrent eluent evaporation.A 10 m 0.53 mm i.d. uncoated, deactivated precolumn wasconnected by a steel T-piece union to the solvent vapour exit(SVE) and a 15 m 0.25 mm i.d. separation column coated witha 0.15 lm film of PS-255 (1% vinyl, 99% methylpolysiloxane)(Mega, Legnano, Italy). A rapid oven gradient (40 C min1) startingfrom 55 up to 350 C was used for GC analysis (Barp et al., 2013).The FID and the SVE were heated at 360 and 140 C, respectively.After the transfer, the LC column was backflushed (dichloromethane)and reconditioned prior to the subsequent injection.The data were acquired and processed by ExaChrom software(Brechbühler, Switzerland). The MOSH area was determined bythe integration of the whole hump of largely unresolved peaks,subtracted from the endogenous n-alkanes. All sharp peaks standingat the top of the MOAH hump were subtracted from the totalarea. Quantification was based on internal standards or on externalstandard, when the presence of sample components co-elutingwith the standards was suspected.
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