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AOAC Official Method 2014.09
Determination and Confirmation of Residues of 653 Multiclass Pesticides
and Chemical Pollutants in Tea
GC-MS, GC-MS/MS, and LC-MS/MS
First Action 2014
Forty representative pesticides were selected based on guidance from the AOAC Method-Centric
Committee on Pesticide Residues to conduct a multilaboratory validation study of the single-laboratory
validated (SLV) method, using two representative brands of tea. The representative pesticides selected
for the multilaboratory validation study of the SLV method are as follows: 2,4'-DDE, 4,4'-DDE, benalaxyl,
bifenthrin, bromophos-ethyl, bromopropylate, chlorfenapyr, diflufenican, dimethenamid, fenchlorphos,
picoxystrobin, pirimicarb, pirimiphos-methyl, procymidone, propyzamide, pyrimethanil, quinoxyfen,
tefluthrin, tolclofos-methyl, and trifluralin by GC-MS and GC-MS/MS; acetochlor, benalaxyl, bensulide,
butralin, chlorpyrifos, clomazone, diazinon, ethoprophos, flutolanil, imidacloprid, indoxacarb, kresoxim-
methyl, monolinuron, picoxystrobin, pirimiphos-methyl, propoxur, quinoxyfen, tebufenpyrad,
triadimefon, and trifloxystrobin by LC-MS/MS.
The LOQs for the 653 pesticides included in the SLV ranged from 0.03 to 1210 μg/kg. The LODs of the GC-
MS method ranged from 1.0 to 500 μg/kg, and the corresponding LOQs ranged from 2.0 to 1000 μg/kg.
The LODs of the GC-MS/MS method ranged from 1.0 to 900 μg/kg, and the corresponding LOQs ranged
from 2.0 to 1800 μg/kg. The LODs of the LC-MS/MS method ranged from 0.03 to 4820 μg/kg, and the
corresponding LOQs ranged from 0.06 to 9640 μg/kg.
Four-hundred eighty-two (482) of the 653 pesticides can be analyzed by GC-MS and GC-MS/MS, while
417 of the 653 pesticides can be analyzed by LC-MS/MS with LODs ≤100 µg/kg. There are 264 out of the
653 pesticides that can be analyzed by GC-MS, and 325 out of 653 by LC-MS/MS with LODs ≤10 µg/kg.
There are 270 pesticides that can be analyzed by both GC-MS and LC-MS/MS. Of these, there are 264
pesticides that can be analyzed by GC-MS and 247 by LC-MS/MS, with LODs ≤100 µg/kg for the GC-MS
method. There are, however, 133 pesticides that can be analyzed by GC-MS and 200 by LC-MS/MS, with
LODs ≤10 µg/kg.
A. Principle
Test samples are extracted with acetonitrile using a homogenizer, and the extracts are cleaned up with
Cleanert TPT cartridge, EnviCarb/PSA or ECPSACB506 (UCT), or BE Carbon 500 g/PSA (Agilent) or InerSep
GC/PSA (GL Sciences), or equivalent cartridges. The pesticides are eluted with acetonitrile-toluene (3 +
1, v/v), concentrated, dried, dissolved in the recommended solution, and analyzed by GC-MS, GC-
MS/MS, or LC-MS/MS and quantified with a matrix-matched standard calibration curve.
B. Reagents
(
a
)
Solvents
.—Acetonitrile, toluene, and
n
-hexane (HPLC grade).
(
b
)
Acetonitrile-toluene.—
3 + 1 (v/v).
(
c
)
Ultrapure water
.--Obtained in a Milli-RO plus system together with a Milli-Q system (Millipore,
(Bedford, MA, USA).
Candidates for 2016 Method of the Year
273