AOAC RI Chemical Cont. Methods-2018 Awards

1444 Pang et al.: J ournal of AOAC I nternational V ol. 98, N o. 5, 2015

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

The minimum point concentrations of calibration curves, μg/kg

No

Pesticide Acetochlor Benalaxyl Bensulide

MRL, μg /kg

Oolong tea

Green tea

LOD, μg/kg

1 2 3 4 5 6 7 8 9

10

20 10 30 10 10 10 10 10 10 10 10 25 50 10 10 10 10

40 20 60 20 20 20 20 20 45 20 20 20 20 50 20 20 20

16

23.7

100

8

0.6

30 20

24

17.1

Butralin

8

1.0

Chlorpyrifos Clomazone

100

100

200

80

26.9

20 20 20 50 50 50

8 8 8 8

0.2 0.4 1.4 0.6

Diazinon

Ethoprophos

Flutolanil

10 11 12 13 14 15 16 17 18 19 20

Imidacloprid Indoxacarb

22.5

18

11.0

8

3.8

Kresoxim-methyl

100

100

200

80

50.3

Monolinuron Picoxystrobin

50

8 8 8

1.8 4.2 0.1

100

Pirimiphos-methyl

50

Propoxur

100

20 40

12.2 76.7

Quinoxyfen Tebufenpyrad Triadimefon Trifloxystrobin

50

100

100 200

8 8 8

0.1 3.9 1.0

50

( 3 )  LC/MS/MS.— For 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. LC/MS/MS, 24

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%.