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© 2015 AOAC INTERNATIONAL
(
2
) The peak area ratios from the different transition reactions
recorded for the analyte and its IS are within the tolerances fixed by
the EU criteria (1) as shown in Table
2015.03E
.
(
d
)
Time of analysis
.—Following this procedure, 20 samples
can be analyzed within 24 h.
H. Calculations and Expression of Results
(
a
)
Calculation
.—Calculate the mass fraction,
w
, of sodium
fluoroacetate in microgram per kilogram of sample (µg/kg), using
the equation:
a
is
is
a
m
m
S
I
A
A
x
w
−
=
where A
a
= peak area of the analyte in the sample (transition
reaction used for quantification); A
is
= peak area of the IS in the
sample (transition reaction used for quantification); I = intercept of
the regression line for the transition reaction used for quantification;
S = slope of the regression line for the transition reaction used for
quantification; m
is
= mass of IS added to the test portion, in ng (i.e.,
10 ng for powdered sample and 50 ng for liquid sample); m
a
= mass
of the test portion, in g (i.e., 1 g for powdered sample and 5 g for
liquid sample).
(
b
)
Expression of results
.—Report the result of sodium
fluoroacetate in µg/kg with one significant figure. Nondetected
amount must be expressed as <1 µg/kg.
I. Performance Characteristics
The method was validated using samples provided by
the AOAC Stakeholder Panel on Infant Formula and Adult
Nutritionals (SPIFAN). Infant formulae considered are described
in Table
2015.03F
.
Validation was performed according to the protocol described in
SANCO/12571/2013 (2): precision data were obtained by spiking
each sample at 1 and 10 µg/kg concentration levels (respectively
corresponding to 1 × LOQ and 10 × LOQ level). At least two
operators were involved in these experiments, each performing five
replicates at the mentioned fortification levels on two different days
(leading to a total of 10 separate experiments for each fortification
level). Nonfortified samples were analyzed as well to verify
absence of the pesticide before fortification trials.
(
a
)
Linearity
.—Linearity was verified over the 0–2 area ratio
range, corresponding to 0–0.8 ng sodium fluoroacetate (0.4 ng IS)
injected on-column. The calibration follows a linear model with R
2
> 0.99 and relative standard deviation of the average of response
factors <15%.
(
b
)
LOQ
.—LOQ is 1 µg/kg for infant formulae. This
concentration corresponds to the lowest fortification level
considered during validation.
(
c
)
Recovery, repeatability, and intermediate reproducibility
precisions
.—Precision data are described in Table
2015.03G
. All
performance data fulfilled SANCO/12571/2013 requirements, i.e.,
both CV(r) and CV(iR) ≤ 20% and recoveries within the 70–120%
range. Exception was recovery for a milk-based formula at the
1 µg/kg fortification level (134%). Asmall peak was observed at the
transition reaction used for quantification in the related unfortified
sample extract, meaning that sodium fluoroacetate might be present
at a concentration well below the quantification capability of this
method. This may explain this higher recovery value.
Table 2015.03D. Typical MS parameters for the analysis of
sodium fluoroacetate
Parameter
Applied Biosystems Sciex 5500
Ionization type
Electrospray (ESI)
Polarity
Negative ionization
Spray voltage
–4500 V
Source block temperature
500°C
Gas
Curtain gas: 30 psi
Ion source gas 1 (GS1): 40 psi
Ion source gas 2 (GS2): 40 psi
Source position adjustments
Vertical micrometer value: 5.0
Horizontal micrometer value: 5.0
Electrode protusion: 1.0 mm
Collision energy (CE)
–15
Entrance potential (EP)
–10 V
Collision exit potential (CXP)
–9 V
Declustering potential (DP)
–45 V
CAD gas pressure (MRM)
Medium (6)
Resolution
High on each quadrupole
Scan time (for each transition)
100 ms
Table 2015.03E
.
Transition reactions monitored for the analysis of sodium fluoroacetate (as its fluoroacetate anion) and its
corresponding IS and peak area ratios along with their limit of acceptance according to CD 2002/657/EC (1)
Transition reactions (
m/z
) used for
Peak area ratio ± limit, %
Quantification
Analyte confirmation
Fluoroacetate
77.0
→
33.0
a
77.0
→
57.0
a
0.80
±
20
13
C
2
-Fluoroacetate (IS)
79.0
→
34.0
79.0
→
59.0
0.68
±
20
a
m/z
57 corresponds to the loss of hydrofluoric acid [M-HF]
-
and
m/z
33 to the loss of carbone dioxide [M-CO
2
]
-
.
Table 2015.03F. Samples considered for the validation
(SPIFAN kit)
Infant formulae
Batch Manufacturer (USA)
Milk-based
K16NTAV PBM Nutritionals
Soy-based
E10NWZC PBM Nutritionals
Partially hydrolyzed milk-based 410057652Z
Nestlé
Partially hydrolyzed soy-based 410457651Z
Nestlé
High-fat nutritional
00729RF00 Abbott Nutrition
High-protein nutritional
00730RF00 Abbott Nutrition
Candidates for 2016 Method of the Year
37