35 / 71
Pang et al.:
J
ournal of
AOAC I
nternational
V
ol.
98, N
o.
5, 2015
1431
(
i
) R
2
for each of the 20 pesticides based on at least a five
point matrix-matched calibration standard curve shall be greater
than 0.995 for GC/MS, GC/MS/MS, or LC/MS/MS
(
ii
) Recoveries shall fall within 70–120% with RSD <15%
(
n
= 5)
(
iii
) Ion abundance of the targeted pesticides should
be in accordance with recommended maximum permitted
tolerances of AOAC guidelines or the EU regulation (EU
Document No. SANCO/10684/2009 Method validation and
QC procedures for pesticide residues analysis in food and
feed and ISO 34)
[
Note
: If ≥30% of the data generated in a laboratory for
recovery, RSD, ion abundance, or R
2
values fail the acceptance
criteria, then the laboratory is considered nonproficient in the
use of the method, and data generated from the laboratory are
excluded from the final analysis and interpretation of the data
generated for the collaborative study.]
(b)
System suitability check.—
Before making determinations
of each consignment sample, use QC standard working
solutions supplied by the Study Director to check the sensitivity
and stability of the instrument.
(
1
)
Instrumental sensitivity (calculated per internal standard
reference S/N)
.—GC/MS >500, GC/MS/MS >1000, and
LC/MS/MS >500.
(
2
)
Instrumental stability (calculated per internal standard
peaks)
.—Retention time deviation <3% (two successive
injections); peak area deviation <10% (two successive
injections).
(
3
) GC/MS, GC/MS/MS, and LC/MS/MS instruments must
all be equipped with a data processing software system.
(c)
Reagent blank and pesticide residue-free (blank
sample) test
.—Confirm that there are no interference peaks
from reagents by running a reagent blank test of the whole
process. Run the reagent blank sample the same as described
in the Collaborative Study Method without adding the sample.
(d)
Calibration check.—
Prepare a five-point matrix-matched
standard calibration curve with internal standard. The R
2
for the
calibration curve must be ≥0.995.
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; and 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.
LOQs
for
the
653
pesticides
included
in the SLV ranged from 0.03 to 1210 μg/kg.
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. 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. 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.
A total of 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.
Figure 1. Number of blank, fortified, incurred, and aged samples for the collaborative study. (Fortified samples are designed per principle of
blinds duplication).