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Mottier:
J
ournal of
AOAC I
nternational
V
ol.
98, N
o
. 4, 2015
1133
(
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%). A small 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.
J. Internal Control Plan
QC samples (certified,
P
-test, in-house reference samples,
or spiked samples) must be regularly included and analyzed in
duplicate.
Spiked experiment
.—Spike the test portion with 20 µL (for
powdered matrices) or 100 µL (for liquid matrices) of standard
working solution 0.05 µg/mL,
C
(
d
), at the same time as the
IS is added,
E
(
a
). This corresponds to 10 µg/kg spiking level.
Calculate the recovery rate (Rec) of the spiked sample using the
following equation:
100
Re
×
−
=
Spiked
N
T
c
ρ
ρ
ρ
where ρ
T
is the total concentration of sodium fluoroacetate
measured in the spiked sample in micrograms per kg. ρ
N
is
the native concentration of sodium fluoroacetate measured
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
Table 2015.03G. Performance characteristics
Sample
Recovery, %
a
CV(r), %
CV(iR), %
1 µg/kg
10 µg/kg
1 µg/kg
10 µg/kg
1 µg/kg 10 µg/kg
Milk-based formula
134
105
6
3
11
4
Soy-based formula
117
103
6
2
8
3
Partially Hydrolyzed milk-based formula
111
108
4
5
9
4
Partially hydrolyzed soy-based formula
116
103
9
2
8
2
High-fat nutritional formula
112
101
4
3
7
4
High-protein nutritional formula
96
99
4
2
6
2
a
Recovery data for sodium fluoroacetate were calculated from values obtained under intermediate reproducibility conditions.
Candidates for 2016 Method of the Year
45