AOAC RI Chemical Cont. Methods-2018 Awards
1436 Pang et al.: J ournal of AOAC I nternational V ol. 98, N o. 5, 2015
Table 2014.09F. LC/MS/MS retention times, ion transitions, collision energies, LODs, and LOQs for the 20 pesticides of interest in this study
Quantifying precursor/ production transition, m / z
Qualifying precursor/ product ion transition, m / z
Retention time, min
Collision energy, V Fragmentation, V LOQ, μg/kg LOD, μg/kg
No.
Pesticide
ISTD Chlorpyrifosmethyl
16.01
322.0/125.0
322.0/290.0
15; 15 10; 10
80 80 80
1 2 3 4 5 6 7 8 9
Imidacloprid
3.81 5.89 6.83
256.1/ 209.1 256.1/175.1
22.0 24.4
11.0 12.2
Propoxur
210.1/111.0 215.1/126.0 240.1/125.0 243.1/173.0 294.2/69.0 270.2/224.0 324.2/262.1 326.2/148.1 314.1/267 368.1/145.0 306.2/164.0 305.0/169.1 398.0/158.1 308.0/197.0 334.3/147.0 528.0/150.0 409.3/186.1 350.0/198.0 296.1/240.1
210.1/168.1 215.1/148.1 240.1/89.1 243.1/215.0 294.2/197.1 270.2/148.2 324.2/282.1 326.2/294.0 314.1/206.0 368.1/205.0 306.2/108.1 305.0/153.2 398.0/314.0 308.0/272.0 334.3/117.1 528.0/218.0 409.3/206.2 350.0/97.0 296.1/222.1
10; 5
Monolinuron Clomazone Ethoprophos Triadimefon Acetochlor
15; 10 20; 50 10; 10 20; 15
100 100 120 100
3.6 0.4 2.8 7.9
1.8 0.2 1.4 3.9
8.3
11.37 11.64 12.94 13.25 14.40 14.58 14.99 15.05 15.20 15, 45 16.60 16.82 16.76 16.82 17.65 17.98
5; 20
80
47.4
23.7
Flutolanil Benalaxyl
20; 10
120 120
1.1 1.2
0.6 0.6
15; 5
10 11 12 13 14 15 16 17 18 19 20
Kresoxim-methyl
5; 5
80 80
100.6
50.3
Picoxystrobin
20; 5
8.4 0.2 0.7
4.2 0.1 0.4
Pirimiphos-methyl
20; 30 20; 20
120 160
Diazinon Bensulide Quinoxyfen Tebufenpyrad
20; 5
80
34.2
17.1 76.7
35; 35 25; 40 20; 20 15; 10 20; 35 10; 20
180 160 120 120 100 100
153.4
0.3 7.5 2.0
0.1 3.8 1.0
Indoxacarb
Trifloxystrobin Chlorpyrifos
53.8
26.9
Butralin
1.9
1.0
( 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 2014.09G. 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, 215.1/148.1 270.2/224.0, 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, 398.0/314.0 334.3/147.0, 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
30
2
12
20
3
16.4
25
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