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© 2015 AOAC INTERNATIONAL
AOAC Official Method 2015.03
Sodium Fluoroacetate in Infant Formula
Liquid Chromatography-Tandem Mass Spectrometry
(LC-MS/MS)
First Action 2015
[Applicable for the quantitative determination of sodium
fluoroacetate in liquid and powdered milk- and soy-based infant
formulas by liquid chromatography-tandem mass spectrometry
(LC-MS/MS). The limit of quantification (LOQ) of sodium
fluoroacetate is 1 µg/kg by this method. Application of this method
to matrices not covered by the scope of application requires an
additional validation.]
Caution
: Material Safety Data Sheets (MSDS) should be available
for all chemicals; inherent risks and corresponding safety
precautions shall be identified.
Follow general safety precautions and environmental
aspects as described in the local Safety, Health and
Environment rules in place.
Sodium fluoroacetate is highly toxic to humans. Take
all necessary precautions, especially when working with
concentrated stock standard solutions.
Sodium fluoroacetate (Figure
2015.03A
) is a synthetic pesticide
known as “1080” and used to fight mammalian pest species. Farmers
and graziers use the poison to protect pastures and crops from
various herbivorous mammals. It is used as well to protect sheep
and goats from predatory coyotes (predacide). In New Zealand and
Australia, it is used to control invasive non-native mammals that
prey on or compete with native wildlife and vegetation. Sodium
fluoroacetate is highly toxic to mammals, including humans. This
pesticide is approved for use in the following countries: United
States, Canada, Mexico, Australia, New Zealand, Korea, Japan,
and Israel. New Zealand has used “1080” for pest control since the
1950s, while the United States began use in the 1940s.
Sodium fluoroacetate is also a naturally occurring poison found
in at least 40 plants native in Australia, South and West Africa, and
Brazil.
A. Principle
Milk powder is first reconstituted in water. Liquid sample
is used as such. Acetonitrile is added to precipitate proteins.
After centrifugation, the supernatant is washed with hexane
and then acidified with concentrated sulfuric acid. QuEChERS
salts (MgSO
4
and NaCl) are added for phase separation and the
mixture is centrifuged. The resulting supernatant is evaporated
to 0.5 mL remaining volume and centrifuged before LC-MS/MS
analysis in selected reaction monitoring (SRM) by electrospray
ionization (ESI) in negative mode. The compound is analyzed as
its fluoroacetate anion.
Quantification is performed by the isotopic dilution approach
using
13
C labeled sodium fluoroacetate as internal standard (IS).
Positive identification of fluoroacetate in samples is conducted
according to the confirmation criteria defined in EU Commission
Decision 2002/657/EC (1).
B. Chemicals and Materials
Commercial references are only a guideline. Use equivalent
chemicals or materials when listed items are not locally available.
(
a
)
Chemicals
.—Before using chemicals, refer to the Sigma-
Aldrich
(www.sigmaaldrich.com)Guide to Chemical Safety and/
or other adequate manuals or safety data sheets approved by your
local authorities and ensure that the safety guidelines are applied.
(
1
)
Water for chromatography
. —CAS No. 7732-18-5 (e.g.,
Merck LiChrosolv
®
art.
15333;
www.emdmillipore.com).
(
2
)
Acetonitrile, hypergrade fo
r LC-MS
.—CAS No. 75-05-8
(e.g., Merck LiChrosolv art. 100029;
www.chemdat.info).
(
3
)
n-Hexane
.—For gas chromatography; CAS No. 110-54-3
(e.g., Merck SupraSolv® art. 104371;
www.chemdat.info).
(
4
)
QuEChERS extraction packets
.—10 g, 200 foil packs per
box, each pack containing 4 g magnesium sulfate (MgSO
4
) and 1 g
sodium chloride (NaCl). CAS Nos. 7487-88-9 and 7647-14-5 (e.g.,
Agilent art. 5982-7550;
www.agilent.com).
(
5
)
Ammonium formate
.—LC-MS ultra, eluent additive for
UHPLC-MS. CAS No. 540-69-2 (e.g., Fluka art. 14266;
www. sigmaaldrich.com).
(
6
)
Sulfuric acid
.—Concentrated,
w
= 95–97%. CAS No. 7664-
93-9 (e.g., Merck art. 100731;
www.merckmillipore.com).
(
7
)
Formic acid
.—Concentrated (e.g., Merck art. 100264;
www. chemdat.info). CAS No. 64-18-6.
(
8
)
Sodium fluoroacetate
.—CAS No. 62-74-8,
w =
99%,
10 µg/mL in water (e.g., Dr. Ehrenstorfer art. DRE-L13772000AL;
www.lgcstandards.com).
(
9
)
13
C
2
-Sodium fluoroacetate
.—
w
= 99%, isotopic purity
>99.5% (e.g., BDG Synthesis art. 130042-10;
http://bdg.co.nz).
(
b
)
Materials
.—
(
1
)
Falcon tubes, conical, polypropylene
.—50 mL (e.g., Becton
Dickinson Labware art. 352070;
www.bdbiosciences.com).
(
2
)
Falcon tubes, conical, polypropylene
.—15 mL (e.g., Becton
Dickinson Labware art. 352097;
http://www.bdbiosciences.com).
(
3
)
Centrifuge with rotors adapted for 50 and 15 mL
tubes.
—4000 ×
g
, temperature controlled (e.g., Multifuge Heraeus;
www.thermo.com).
(
4
)
Vortex
.—e.g., Millian Genie 2
(http://www.milian.com).
(
5
)
Centrifuge with rotor adapted for 2 mL tubes
.—17000 ×
g
(e.g., Heraeus Frisco 17;
www.thermoscientific.com).
(
6
)
Microcentrifuge tubes, polypropylene
.—2 mL (e.g., Trefflab
art. 9607246901;
www.treff-ag.ch).
(
7
)
Analytical balance.—
With precision range 0.01 mg
.
(
8
)
Shaker
.—GenoGrinder Model 2010
(www.spexsampleprep. com).
(
9
)
Evaporator
.—e.g., Reacti-Vap Evaporator (art. TS-18825;
www.thermo.com).
(
c
)
Special equipment and instrumentation
.—Where a specific
model is cited, an alternative may be used if it has the same
characteristics.
(
1
)
HPLC system
.—Agilent 1200 SL
(www.agilent.com)coupled to a Sciex 5500 triple stage quadrupole mass spectrometer
Figure 2015.03A. Chemical structure of sodium
fluoroacetate (NaFC
2
H
2
O
2
;
CAS No. 62-74-8; MW 100 g/mol).
_______________________
_____________________________________________
1
Anita Mishra, Executive, Scientific Business Devel pment,
amishra@aoac.orgDeborah McKenzie, Senior Director, Approv l Processe
s & AOAC Research Institute, dmckenzie@aoa
Bob Rathbone, Senior Director, Publica ions, rrathbone@a
ac.org© 2015 AOAC INTERNATIONAL
while the United States began use in the 1940's.
Sodium fluoroacetate is also a naturally occurring poison found in at least 40 plants n
Australia, South and West Africa and Brazil.
Figure 1.
Chemical structure of sodium fluoroacetate
(NaFC
2
H
2
O
2
;
CAS 62-74-8; MW 100 g/mol)
ONa
O F
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