Page 26 - Volume 6, Issue 2, July 2013

© Benaki Phytopathological Institute
Bempelou et al. 74
determination of diazinon and its metabo-
lite IMP from the mineral salts medium and
diazinon from tomato fruits and ensure the
accuracy of the results from the biodegrada-
tion trials.
Up to now, the simultaneous determina-
tion of the two compounds has been report-
ed in various substrates (water, soil, plants,
products of animal origin, urine and blood
plasma mainly using high performance
liquid chromatography with UV detector
(HPLC/UV) (Abu- Qare et al., 2001; Abu- Qare
and Abou- Donia, 2001), as well chromatog-
raphy with FID detector (Bavcon et al., 2003).
In agreement to our analytical method Rain
and Sun (2008) reported the determination
of diazinon and IMP by liquid chromatogra-
phy-positive ion electrospray tandem mass
spectrometry.
Biodegradation of diazinon by Rhodo-
torula glutinis and Rhodotorula rubra
Effect of yeast inoculum on biodegradation
No biodegradation was observed when
10 2 cells/mL and 10 4 cells/mL of Rh. glutinis
and Rh. rubra were supplemented in the
mineral salts nutrient medium, up to the
end of the experimental period. On the con-
trary, degradation did occur after the incu-
bation of each culture with the initial inocu-
lum of 106 cells/mL and in this case IMP was
detected as a degradation product. In con-
trast to our study Sethunathan (1989), who
also verified degradation products of diazi-
non after the incubation with the bacterium
Flavobacterium sp. ATCC27551 in rice fields,
found the metabolite 2-isopropyl-4-meth-
yl-6-hydroxypirimidine (IMHP) was the ma-
jor metabolite.
Effect of presence of glucose onmineral salts
liquid medium
The addition of glucose in the mineral
salts nutrient medium, as an extra source of
carbon, affected the action of Rhodotorula
yeasts as degraders of diazinon in a different
way. Under the presence of glucose, Rh. glu-
tinis did not consume diazinon during the
first days of the trials, while after the fourth
day the insecticide was decreased rapidly
(Figure 2). On the contrary, in the flasks with-
out glucose degradation was observed from
the first sampling (day 2) of the trials and di-
azinon was finally depleted. In agreement
with our results, Muncnerova and Augustin
(1995) had reported the degradation of ben-
zoate by Rh. glutinis only after the consump-
tion of glucose in the medium. According
to Ruiz-Amil et al. (1965); Torrontegui et al.
(1966), Fernadez et al. (1967) and Medrano et
al. (1969) the presence of glucose in the nu-
Table 1. Mean recoveries (R, %), relative standard deviations (RSD, %) and signal to noise
(S/N) ratio for the determination of diazinon and 2-isopropoyl-6-methyl-4-pyrimidinol (IMP)
in mineral salts medium and diazinon in tomato fruits, in 5 replicates (n) at 3 fortification lev-
els in the LC-MS/MS chromatographic system.
Compound
Mineral salts medium
(n=5)
Tomato fruits
(n=5)
C
(μg/mL)
MeanRecovery
(%)
RSD (%) S/N C
(μg/mL)
MeanRecovery
(%)
RSD (%) S/N
Diazinon
0.05
0.1
0.5
95.6
91.4
100
0.34
2.8
1.6
47
53
112
0.05
0.1
0.5
97.6
91.4
102
1.7
2.8
4.7
32
93
124
IMP
0.05
0.1
0.5
85.2
93
96.6
3.55
2.79
2.06
17
32
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