40 / 71
1436
Pang et al.:
J
ournal of
AOAC I
nternational
V
ol.
98, N
o.
5, 2015
(
2
) Measure the ion abundances for the qualifier ions for the
detected pesticides and verify that they are within the expected
limits. If the peaks match, the presence of the pesticide is
confirmed.
See
Table
2014.09H
.
(b)
Quantitative calculations.—
(
1
) Use instrument data
processing software for GC/MS (SIM), GCMS/MS, and/or
LC/MS/MS to calculate a response ratio (measured abundance
of pesticide/measured abundance of heptachlor epoxide for
GC and chlorpyrifos methyl for LC) and construct a five-point
matrix-matched calibration curve of response ratio versus
concentration of pesticide in standard solution.
(
2
) Using the regression data from the appropriate matrix-
matched calibration curve, calculate the concentration of each
pesticide found in the samples.
(
3
) If a validated computer system is not being used for
calculations, follow the steps below:
(
a
) Measure the peak area of each respective standard level
for each pesticide and the peak area of corresponding ISTD.
(
b
) Calculate the ratio of the analyte response to that of the
ISTD.
(
c
) Run a linear regression analysis using the ratio of each
pesticide at five different levels with no weighting or 1/x
weighting, where x = concentration.
(
d
) Measure the peak area of each pesticide found in the
sample and the peak area of corresponding ISTD.
(
e
) Calculate the amount of each pesticide in the solution
injected from the standard curve.
(
f
) Calculate the amount of each pesticide present in the
sample.
Test results should be reported to two decimal places or four
significant digits.
Table 2014.09F. LC/MS/MS retention times, ion transitions, collision energies, LODs, and LOQs for the 20 pesticides of
interest in this study
No.
Pesticide
Retention
time, min
Quantifying
precursor/
production
transition,
m
/
z
Qualifying
precursor/
product ion
transition,
m
/
z
Collision
energy, V Fragmentation, V LOQ, μg/kg LOD, μg/kg
ISTD Chlorpyrifosmethyl
16.01
322.0/125.0
322.0/290.0
15; 15
80
1
Imidacloprid
3.81
256.1/ 209.1 256.1/175.1
10; 10
80
22.0
11.0
2
Propoxur
5.89
210.1/111.0
210.1/168.1
10; 5
80
24.4
12.2
3
Monolinuron
6.83
215.1/126.0
215.1/148.1
15; 10
100
3.6
1.8
4
Clomazone
8.3
240.1/125.0
240.1/89.1
20; 50
100
0.4
0.2
5
Ethoprophos
11.37
243.1/173.0
243.1/215.0
10; 10
120
2.8
1.4
6
Triadimefon
11.64
294.2/69.0
294.2/197.1
20; 15
100
7.9
3.9
7
Acetochlor
12.94
270.2/224.0
270.2/148.2
5; 20
80
47.4
23.7
8
Flutolanil
13.25
324.2/262.1
324.2/282.1
20; 10
120
1.1
0.6
9
Benalaxyl
14.40
326.2/148.1
326.2/294.0
15; 5
120
1.2
0.6
10
Kresoxim-methyl
14.58
314.1/267
314.1/206.0
5; 5
80
100.6
50.3
11
Picoxystrobin
14.99
368.1/145.0
368.1/205.0
20; 5
80
8.4
4.2
12
Pirimiphos-methyl
15.05
306.2/164.0
306.2/108.1
20; 30
120
0.2
0.1
13
Diazinon
15.20
305.0/169.1
305.0/153.2
20; 20
160
0.7
0.4
14
Bensulide
15, 45
398.0/158.1
398.0/314.0
20; 5
80
34.2
17.1
15
Quinoxyfen
16.60
308.0/197.0
308.0/272.0
35; 35
180
153.4
76.7
16
Tebufenpyrad
16.82
334.3/147.0
334.3/117.1
25; 40
160
0.3
0.1
17
Indoxacarb
16.76
528.0/150.0
528.0/218.0
20; 20
120
7.5
3.8
18
Trifloxystrobin
16.82
409.3/186.1
409.3/206.2
15; 10
120
2.0
1.0
19
Chlorpyrifos
17.65
350.0/198.0
350.0/97.0
20; 35
100
53.8
26.9
20
Butralin
17.98
296.1/240.1
296.1/222.1
10; 20
100
1.9
1.0
Table 2014.09G. SRM acquisition parameters by LC/MS/MS analysis for the 20 pesticides
Group
Start time, min
Monitored ion transitions,
m
/
z
Dwell time, ms
1
0
256.1/209.1, 256.1/175.1, 210.1/111.0, 210.1/168.1, 240.1/125.0, 240.1/89.1, 243.1/173.0,
243.1/215.0, 294.2/69.0, 294.2/197.1, 215.1/126.0, 215.1/148.1
30
2
12
270.2/224.0, 270.2/148.2, 306.2/164.0, 306.2/108.1, 324.2/262.1, 324.2/282.1, 326.2/148.1,
326.2/294.0, 305.0/169.1, 305.0/153.2, 314.1/267.0, 314.1/206.0, 322.0/125.0, 322.0/290.0,
368.1/145.0, 368.1/205.0, 398.0/158.1, 398.0/314.0
20
3
16.4
334.3/147.0, 334.3/117.1,528.0/150.0,528.0/218.0, 409.3/186.1, 409.3/206.2,296.1/240.1,
296.1/222.1, 350.0/198, 350.0/97.0, 308.0/197.0, 308.0/272.0
25