Page 43 - Volume 3, Issue 2, July 2010
Basic HTML Version
© Benaki Phytopathological Institute
Anagnostopoulos
et al.
74
The oven temperature programme start-
ed from 60
o
C for 1.5 min, increased to 220
o
C
at a rate of 14
o
C/min, held for 4 min then in-
creased to 280
o
C at 20
o
C/min and held for
20 min. The helium carrier gas flow rate was
1.5 ml/min for both columns.
Injectors’ tem-
perature was set at 230
o
C and splitless in-
jection was carried out with the purge valve
closed for 1 min. Hydrogen (3 ml/min) and
air (60 ml/min) were used as fuel gases for
the NPD. Temperature was set at 310
ο
C for
both detectors.
Results and discussion
The method was found to be effective for
extraction of the tested compounds. The
method was validated by assessing the ba-
sic parameters, sensitivity, mean recovery
(as a measure of trueness) and repeatability
(as a measure of precision). These parame-
ters were evaluated for both detectors.
The confirmation of the analytes was
conducted, as mentioned earlier, only by
the retention time of the analyte using two
columns of different polarity and two differ-
ent detectors. The retention times acquired
for each analyte using a combination of two
different columns and two different detec-
tors are shown in Table 1. Because the de-
tectors used (ECD and NPD) offer a degree of
selectivity, the use of two columns in combi-
nation with these detectors was necessary
to achieve sufficient confirmation. As shown
in Table 1, confirmation was achieved suc-
cessfully for all analytes. For organochloride
pesticides, confirmation was achieved using
Table 1.
Pesticides studied, retention times of the analytes with DB-5-MS and DB-17-MS col-
umns and sensitivity to ECD and NPD detectors.
Analytes
DB-5- MS
DB-17-MS ECD sensitivity NPD sensitivity
aldrin
12.0
14.0
+
-
cadusafos
7.6
8.6
+
+
demeton-s-methyl
7.1
8.9
-
+
demeton-s-methyl sulfone
11.1
19.2
-
+
demeton-s-methyl sulfoxide
7.0
4.5
-
+
dieldrin
16.9
22.0
+
-
dimethoate
8.2
12.3
+
+
disulfoton
9.2
11.3
+
+
disulfoton-sulfone
15.7
24.1
+
+
disulfoton-sulfoxide
5.1
5.5
+
+
ethoprophos
6.9
8.3
+
+
fensulfothion
19.3
29.4
+
+
fensulfothion sulfone
20.5
30.7
+
+
fensulfothion-oxon
17.4
27.9
+
+
fensulfothion-oxon-sulfone
18.4
29.2
+
+
fipronil
14.6
16.2
+
+
fipronil-desulfinyl
10.9
11.8
+
+
heptachlor
10.8
12.5
+
-
heptachlor epoxid (trans)
13.9
17.4
+
-
hexachlorobenzene
8.1
9.2
+
-
nitrofen
18.3
25.6
+
+
omethoate
6.7
9.7
-
+
terbufos
8.7
10.1
+
+
terbufos-sulfone
14.0
20.3
+
+
terbufos-sulfoxide
8.6
10.0
-
+
