2. AOACRIChemContMethods-2018Awards

Pang et al.: J ournal of AOAC I nternational V ol. 98, N o. 5, 2015  1433

Table 2014.09A. GC/MS retention times, quantifying ions, qualifying ions, ion abundances, LODs, and LOQs for the 20 pesticides

Retention time, min

Quantifying ion, m / z

Qualifying ion 1, m / z

Qualifying ion 2, m / z

LOQ, μg/kg

LOD, μg/kg

No.

Pesticide

ISTD a

353(100) b 306(100) 177(100) 198(100) 173(100) 166(100) 154(100) 265(100) 285(100) 290(100) 246(100) 359(100) 318(100) 283(100) 335(100) 247(100) 237(100) 148(100) 181(100) 266(100) 341(100)

Heptachlor-epoxide

22.15 15.43 17.35 17.43 18.94 19.00 19.77 19.83 19.90 20.37 22.75 23.12 23.95 24.57 24.79 27.40 27.15 27.68 28.62 28.73 29.46

355(79) 264(72) 197(26) 199(45) 255(23) 238(23) 230(43) 267(36) 287(69) 276(86) 318(34) 303(77) 316(80) 285(70) 303(43) 328(54) 272(37) 206(32) 166(32) 394(25) 183(54)

351(52) 335(7) 161(5) 200(5) 240(9) 138(8) 203(21) 250(10) 270(6) 305(74) 176(26) 357(74) 246(139) 255(15) 367(9) 408(51) 307(29) 325(8) 165(35) 267(14) 339(51)

1 2 3 4 5 6 7 8 9

Trifluralin Tefluthrin

20.0 10.0 10.0 10.0 20.0 10.0 10.0 40.0 20.0 25.0 10.0 10.0 10.0 20.0 10.0 10.0 10.0 10.0 20.0

10.0

5.0 5.0 5.0

Pyrimethanil Propyzamide

Pirimicarb

10.0

Dimethenamid Tolclofos-methyl Fenchlorphos Pirimiphos-methyl

5.0 5.0

20.0 10.0 12.5

10 11 12 13 14 15 16 17 18 19 20

2,4 ' -DDE

Bromophos-ethyl

5.0 5.0 5.0

4,4 ' -DDE

Procymidone Picoxystrobin Chlorfenapyr Quinoxyfen

10.0

200.0

100.0

5.0 5.0 5.0 5.0

Benalaxyl Bifenthrin

Diflufenican

Bromopropylate

10.0

a  ISTD = Internal standard. b  Numbers in parentheses are ion abundances.

parameters for the precursor and product ion transitions monitored by GC/MS/MS are shown in Table 2014.09D . (c) LC/MS/MS analysis.— ( 1 )  LC/MS/MS system .—An Agilent Series 1200 HPLC system directly coupled to a 6430 triple quadrupole mass spectrometer equipped with an electrospray ionization source and Model G1367D autosampler with a Mass Hunter data processing software system (Agilent Technologies). ( 2 )  Column .—Zorbax SB-C18, 2.1 × 100 mm × 3.5 μm, or equivalent. ( 3 )  Mobile phase gradient elution program and flow rate .— See Table 2014.09E . ( 4 )  Column temperature .—40°C.

( 6 )  Injection volume .—1 μL. ( 7 )  Injection mode .—Splitless, purge on after 1.5 min. ( 8 )  Ionization mode .—EI. ( 9 )  Ion source polarity .—Positive ion. ( 10 )  Ionization voltage .—70 eV. ( 11 )  Ion source temperature .—230°C. ( 12 )  GC/MS interface temperature .—280°C. ( 13 )  Solvent delay .—14 min. ( 14 )  Ion monitoring mode .—Selected ion monitoring (SIM); one quantifying ion and two qualifying ions are selected for each compound. The retention times, quantifying ions, qualifying ions, and the expected ion abundances for each of the 20 pesticides included in the study and heptachlor epoxide are listed in Table 2014.09A . SIM acquisition parameters for ions monitored by GC/MS are shown in Table  2014.09B . (b) GC/MS/MS analysis.— ( 1 )  GC/MS/MS system .—Model 7890A gas chromatograph connected to a Model 7000B triple quadrupole mass spectrometer with EI source and equipped with a Model 7693 autosampler and Mass Hunter data processing software system (Agilent Technologies), or equivalent. ( 2 ) Operating conditions are the same as for GC/MS with the exception that the ion monitoring mode is by selected reaction monitoring (SRM) and monitoring one precursor ion and two product ion transitions. ( 3 ) The monitored ion transitions and the collision energies for the 20 pesticides of interest in the study and heptachlor epoxide are shown in Table 2014.09C . The SRM acquisition

( 5 )  Injection volume .—10 μL. ( 6 )  Ionization mode .—ESI. ( 7 )  Ion source polarity .—Positive ion. ( 8 )  Nebulizer gas .—Nitrogen gas. ( 9 )  Nebulizer gas pressure .—0.28 Mpa. ( 10 )  Ion spray voltage .—4000 V. ( 11 )  Dry gas temperature .—350°C. ( 12 )  Dry gas flow rate .—10 L/min.

( 13 ) Monitored ion transitions, collision energies, and fragmentation energies for the 20 pesticides and chlorpyrifos methyl are shown in Table 2014.09F , and SRM acquisition parameters by LC/MS/MS for the precursor and product ion transitions monitored are shown in Table 2014.09G .