A. Boudina et al. / Chemosphere 68 (2007) 1280–1288
1287
Richard (1998) have reported a similar reaction concerning
ESI
electrospray ionization
the photodegradation of 3-hydroxy-benzonitrile in water
since 3-hydroxybenzaldehyde was obtained at all pHs
tested. In our case, the photoproducts seem to retain the
(E/Z) isomerism of their precursor, with the E-isomer
(Compound J) obtained in higher yield than the Z-isomer
(Compound H).
APCI atmospheric pressure chemical ionization
(M+H)+ molecular peak detected with ESI or APCI in
positive mode
(MꢀH)ꢀ molecular peak detected with ESI or APCI in
negative mode
E.C.E.T.O.C European Chemical Industry & Toxicologi-
cal Centre
3.4. Kinetics of the main photoproducts
Acknowledgements
Fig. 4a shows kinetic curves for AZX, A, B, C, and G
obtained after irradiation of AZX using the xenon lamp
and followed by HPLC–DAD. Almost 72.7% of AZX is
degraded to some other form after 221 h of irradiation with
compound G being the most prominent chromatographic
peak area. Both photoproducts B and A seems to appear
at low concentration immediately upon irradiation and
accumulate in the solution without any further degrada-
tion. Using chemical standards, 1.29 lM concentrations
of photoproduct B were confirmed after 221 h of irradia-
tion, a level maintained for all times after 20–25 h. The
product C appears in the last position meaning that surely
it comes from other photoproducts.
Fig. 4b shows the evolution of photoproducts E, F, H, I,
and J which appear following the photo-isomerization
reaction 20–25 h after the start of irradiation. We hypoth-
esize that AZX gives rise to E which in turn is transformed
into F. These photoproducts also seem to be quite stable
from the photochemical point of view.
The authors are grateful to Robert BAUDOT (S.C.A.)
for HPLC/MS analyses and for helpful suggestions in the
spectra interpretations. We thank Dr. Thomas CUSTER
from Max-Planck-Institute for Chemistry in Mainz, Ger-
many for improving the English of the manuscript. Finally,
The Editor and Reviewers are thanked for their effort and
contribution to the improvement of the paper content.
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Abbreviations
AZX azoxystrobin
ek
t1/2
s
molar extinction coefficient
time of half reaction (ln2/k)
photolytic life-time
/
Rt
quantum efficiency
Retention times