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Joseph et al.
: J
ournal of
AOAC I
nternational
Vol. 98, No. 3, 2015
(
26
) Decant the supernatant into a clean 15 mL tapered,
polypropylene tube.
(
27
) Evaporate the solvent to incipient dryness under
nitrogen at 40 ± 10°C.
Note
: Do not leave on heating block as excess heating may
degrade derivatized analyte.
(
28
) Allow tubes to return to near room temperature and then
redissolve residue in 150 µL acetonitrile.
(
29
) Vortex mix at low speed.
(
30
) Centrifuge at 2400 ×
g
RCF for 1 min.
(
31
) Transfer clear solvent layer to a tapered insert in an
autosampler vial, making sure not to transfer any solid and/or
particulate matter. Cap firmly.
Note
: Final extracts have been shown to be stable at least
5 days when stored in the freezer at –10°C or below.
(
c
)
Instrumental
determination
.—(
1
)
Identification
parameters
.—Identification parameters for the analysis of
sodium fluoroacetic acid are given in Table
2015.02B
.
(
2
)
Analytical
instrumentation
.—(
a
)
General
.—Agilent
1290 HPLC system coupled with a 5500 QTRAP Triple Quad
Mass Spectrometer. The system is controlled by ABSciex
Analyst software. Peak integration is handled with ABSciex
MultiQuant Analysis software.
Note
:
See
Figure
2015.02B
for exemplary chromatograms.
(
b
)
LC parameters
.—
See
Table
2015.02C
for HPLC solvent
gradient.
(
i
)
Column
.—Agilent XDB-C18 100 × 4.6 mm.
(
ii
)
Guard column
.—Phenomenex Security C18, 4 × 2 mm.
(
c
)
Mass spectrometer parameters
.—
See
Table
2015.02D
for full analytical parameters.
G. Calculations
Quantification of fluoroacetic acid is based on peak area.
Matrix recoveries are used to generate calibration curves. An
unknown peak that falls within the evaluation window (as
calculated by recoveries and internal standard) is quantified
from the appropriate calibration curve and the value tabulated,
together with peak identification information. Each potential
unknown is then manually assessed for the quality of
identification by viewing integrated chromatograms and those
of any qualifying ions.
C
u
=
RR
/
Sl
where
C
u
= concentration of unknown sample in µg/kg;
RR
=
relative response of unknown sample;
Sl
= slope of calibration
curve.
H. Method Performance and Quality Control
(
a
)
Reagent blank test
.—A reagent blank (deionized water)
test is performed with each batch.
(
b
)
Matrix standard test
.—Performed with each batch
according to Table
2015.02A
.
(
c
)
Matrix blank test (Recovery 1)
.—A matrix blank test is
performed with each batch.
(
d
)
Matrix recovery test (recovery samples)
.—Performed
with each batch according to Table
2015.02A
.
(
e
)
Certified reference materials (CRM)
.—No CRM is
currently available. In practice, external checks of the method
are performed by participation in interlaboratory calibration
studies when available.
(
f
)
Performance values
.—Values found in Table
2015.02E
are calculated from the in-house single-laboratory validation
(SLV)completed by AsureQuality Ltd.
(
g
)
Acceptance criteria
.—(
1
)
Individual sample acceptance
criteria
.—The internal standard response for an individual
sample should exceed 33% of the mean internal standard
response of the recovery samples.
(
2
)
Batch acceptance criteria
.—Analyte relative recoveries
for the recovery samples should be within 3 SD of the mean
relative recovery established from control charts. Calibration
curves should have a coefficient of determination R
2
> 0.95.
(
3
)
Positive sample acceptance criteria
.—Retention time
acceptance criteria are given in Table
2015.02F
. Ion ratio
acceptance limits are given in Table
2015.02G
.
(
h
)
Control charts
.—Control charts are to be maintained
for the method by plotting the relative recovery of the matrix
standard quantified from the slope of the recovery curve.
References
(1) New Zealand (Maximum Residue Limits of Agricultural
Compounds) Food Standards 2015 (February 20, 2015)
NZ
Gazette
18
(2)
Off. J. Eur. Commun
.
L221
,
8(2002)
(3) AOAC SMPR 2015.001
J. AOAC Int
. (future issue)
Table 2015.02G. Ion ratios and limits of acceptance
Compound (3-nitroaniline derivative of analyte)
Transitions
MRM ratio
a
Acceptance limit, %
b
2-Fluoro-3
ʹ
-nitroacetanilide
196.9 → 146.9/196.9 → 122.0
1.01
±20
196.9 → 117.8/196.9 → 122.0
0.75
±20
a
Representative MRM ratio. These values are indicative and should be measured for each individual batch.
b
See
reference 2.
245