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was bolted to a main pressure line while the internal a thermocouple was
attached to a temperature reader. The autoclave was heated to 350 °C and the
hydraulic pressure adjusted to 700 Bars. After 24 h, the reactor was removed,
cooled to room temperature within 5 min by a heat exchanger. The gold cells
were removed and then weighed to record any difference in weight before and
after the experiment.
Following this they were analysed by pyrolysis-gas chromatography-mass spec-
trometry (py-GC/MS) at 610 °C (for experimental parameters see Gupta and Pancost
2004
). No absolute quantifi cation was attempted. Selected experimental samples
were subjected to base hydrolysis (for 3 h) after solvent extraction to evaluate fur-
ther the nature of the maturation products (Table
5.1
).
Implications
Pyrolysis-GC/MS of extracted but otherwise untreated leaves (Fig.
5.2a
) other than
A. americana
yielded chromatograms dominated by carbohydrate, lignin (guaiacyl
and syringyl related components) and protein moieties, together with C
16
and C
18
fatty acids, refl ecting the bulk composition of the leaf (Ralph and Hatfi eld
1991
; Van
Bergen et al.
1998
; Gupta and Pancost
2004
). The fatty acyl moieties are derived
from internal lipids and from the biopolyester cutin. With the exception of
Agave
,
none of the examined leaves contain cutan (Gupta et al.
2006a
). Except for
Agave
,
all the other leaves investigated gave similar results and therefore the discussion
focusses on
Castanea
.
Leaves matured without any chemical pre-treatment (Fig.
5.2b
) yielded chro-
matograms dominated by
n
-alkane/
n
-alk-1-ene homologues, indicating the pres-
ence of an
n
-alkyl component in the post-maturation leaf. The
n
-alkanes ranged
from C
9
to C
31
and the
n
-alkenes from C
9
to C
29
. The most abundant
n
-alkanes were
the C
15,
C
17,
C
27,
C
29
and C
31
homologues. Of the fatty acids generated during pyroly-
sis, the C
16
and C
18
straight-chain homologues were the most abundant, with straight
chain C
12
, C
13
, C
14
, and C
15
components also detected. Apart from the aliphatics,
other important pyrolysis products included phenol and its alkyl derivatives, ben-
zene and its alkyl derivatives, and indoles (possibly derived from proteins). The
guaiacyl and syringyl related lignin moieties evident in the unmatured leaf tissue
were not observed in detectable amounts in the matured leaves, presumably due to
decomposition of lignin during the experiment.
Matured leaves were solvent-extracted and saponifi ed, with subsequent analysis
of the non-hydrolysable residue revealing that the polymeric components yielding
alkane/alkene homologues (up to C
18
) persisted (Fig.
5.3
, Table
5.1
). The C
13
, C
15
and C
17
n
-alkanes and the C
10
, C
12
, C
13
and C
14
n
-alkenes were the most abundant
components in their respective classes. This indicates that a signifi cant portion of
the aliphatic polymer is resistant to base hydrolysis and confi rms that it is not an
artefact of pyrolysis. Thus, the macromolecule in matured leaf tissue is resistant to
degradation and at least partly aliphatic. However, non-hydrolysable and aliphatic
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