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Pang et al.:
J
ournal of
AOAC I
nternational
V
ol.
98, N
o.
5, 2015
Qualification and Quantification
The collaborative study protocol stipulates that the deviations
of qualifying ion abundance of the target pesticides shall have to
comply with EU standards. For this collaborative study, GC/MS,
GC/MS/MS, and LC/MS/MS were used by 29 laboratories for
the determination of pesticide residues in green tea and oolong
tea (excluding blank samples), with 10 231 target ion abundance
ratio data obtained, and ion abundance ratios checked item by
item against EU standard confirmation criteria, with results
tabulated in Supplemental Tables 15–17 on the
J. AOAC Int.
website.
(a)
Qualification of target pesticides.
—(
1
)
GC/MS.—
SupplementalTables 15–17 showthat forGC/MS, 16 laboratories
participated in the study: a total of 4414 (2324 + 2090)
target pesticide ions were obtained from analysis of green tea
and oolong tea samples, among which the ion abundance ratios
that comply with EU standards reached 4154 (2229 + 1925),
accounting for 94%.
(
2
)
GC/MS/MS.—
For
GC/MS/MS,
14
laboratories
participated in the study: a total of 2268 (1041 + 1227) target
pesticide ions were obtained from analysis of green tea and
oolong tea, among which the ion abundance ratios that comply
with EU standards reached 2247 (1032 + 1215), accounting
for 99%.
(
3
)
LC/MS/MS.—
For
LC/MS/MS,
24
laboratories
participated in the study: a total of 3549 (1819 + 1730) target
pesticide ions were obtained from analysis of green tea and
oolong tea samples, among which the ion abundance ratios that
comply with EU standards reached 3494 (1794 + 1700), making
up 98%.
The above-mentioned data reveal that a total of 10 231 of
target pesticide ions were obtained by the 29 participating
laboratories, among which the ion abundance ratios that comply
with EU standards reached 9895, accounting for 97%, which
proves that the said method enables accurate qualification
inspection for the majority of pesticides by different laboratories
using different instruments.
(b)
Quantificationof target pesticides.—
For this collaborative
study, matrix-matched calibration standards containing an
appropriate ISTD were used for quantitative analysis of the
samples tested in the collaborative study. In all, 2153 target
pesticide calibration curves established by 29 laboratories were
used to perform the quantitative analysis in the study. The R
2
≥0.995 are tabulated in Supplemental Table 18.
(
1
)
GC/MS.—
Supplemental Table 18 shows that concerning
GC/MS: 16 laboratories established 639 matrix-matching ISTD
calibration curves, respectively, for 20 pesticides in green tea
and oolong tea, among which those with R
2
≥0.995 reached
637, accounting for 99.7%; one had R
2
between 0.990 and
0.995, one R
2
less than 0.990.
Pang
et al.:
J
ournal of
AOAC I
nternational
V
ol.
98, N
o.
5, 2015
144
Table 8. The MRL, fortified concentration, LOD, and the minimum point concentrations of calibration curves for fortified
samples by LC/MS/MS
Fortified concentration, μg/kg
No
Pesticide
MRL, μg /kg
Oolong tea
Green tea
LOD, μg/kg
The minimum point
concentrations of
calibration curves, μg/kg
1
Acetochlor
10
20
40
16
23.7
2
Benalaxyl
100
10
20
8
0.6
3
Bensulide
30
30
60
24
17.1
4
Butralin
20
10
20
8
1.0
5
Chlorpyrifos
100
100
200
80
26.9
6
Clomazone
20
10
20
8
0.2
7
Diazinon
20
10
20
8
0.4
8
Ethoprophos
20
10
20
8
1.4
9
Flutolanil
50
10
20
8
0.6
10
Imidacloprid
50
22.5
45
18
11.0
11
Indoxacarb
50
10
20
8
3.8
12
Kresoxim-methyl
100
100
200
80
50.3
13
Monolinuron
50
10
20
8
1.8
14
Picoxystrobin
100
10
20
8
4.2
15
Pirimiphos-methyl
50
10
20
8
0.1
16
Propoxur
100
25
50
20
12.2
17
Quinoxyfen
50
50
100
40
76.7
18
Tebufenpyrad
100
10
20
8
0.1
19
Triadimefon
200
10
20
8
3.9
20
Trifloxystrobin
50
10
20
8
1.0