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© 2015 AOAC INTERNATIONAL
(
24
) Add approximately 200 mg sodium sulfate, anhydrous, to
each tube and vortex mix.
(
25
) Centrifuge at 2400 ×
g
RCF for 1 min.
(
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 AB Sciex Analyst
software. Peak integration is handled with AB Sciex 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.Anunknown 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
.
Table 2015.02F. Relative retention time (RRT) and limits of acceptance
Compound (3-nitroaniline derivative of analyte)
Monitored compounds
RRT
Acceptance limit
a
2-Fluoro-3
ʹ
-nitroacetanilide
Analyte/internal standard
1.004
b
RRT ± 2.5%
a
See
reference 2.
b
Representative relative retention time. These values are indicative and should be measured for each individual batch.
Table 2015.02E. Performance values of analytes
a
Compound
LOD, µg/kg LOQ, µg/kg LOR, µg/kg Within-day CV
Between-day CV
(WLR)
U
(for 95% CI)
Recovery, %
(SD)
Fluoroacetic acid
0.028
0.085
1.0
b
8.8
9.1
18
97
c
(8.8)
13
C
2
D
2
Fluoroacetic acid
NA
NA
NA
NA
NA
NA
70
d
(12)
a
LOD = Limit of detection; LOQ = limit of quantification; CV = coefficient of variation; WLR = within-laboratory reproducibility; U = uncertainty of measurement
with a 95% confidence interval; SD = standard deviation.
b
Limit of reporting (LOR) set according to New Zealand maximum permitted residue limits.
See
reference 1.
c
Relative recovery.
d
Absolute recovery.
Candidates for 2016 Method of the Year
24