53 / 363
1136
Reddy
: J
ournal of
AOAC I
nternational
Vol. 98, No. 4, 2015
(
h
)
Centrifuge tubes
.—2, 15, and 50 mL.
(
i
)
Spatulas and scoops
.
(
j
)
Centrifuge
.—Thermo Fisher Scientific
(http://www. thermofisher.com)Sorvall Legend XTR, or equivalent.
(
k
)
Glass centrifuge tubes with screw cap
.—VWR (Cat.
Nos. 99502-15 and 89001-048, respectively;
https://www.vwr.com).
(
l
)
Water bath
.—Thermo Fisher Scientific Precision model
2872, or equivalent.
(
m
)
Glass Pasteur pipets
.
(
n
)
Vacuum manifold for SPE
.
(
o
)
SPE cartridges
.—Supelclean Envi-Chrom P, 500 mg,
6 mL (Cat. No. 57226; Sigma-Aldrich, https://www.
sigmaaldrich.com).
(
p
)
SPE cartridge reservoirs
.—25 mL (Supelco; Cat.
No. 54258-U).
(
q
)
Positive displacement pipets
.—Gilson
(http://www. gilson.com)Microman (M); Model Nos. M10, M100, M250,
and M1000. Part Nos. F148501, F148504, F148505, and
F148506.
(
r
)
Positive displacement pipet tips
.—Gilson Capillary
Piston (CP); Reference Nos. CP10, CP25, CP100, CP250, and
CP1000. Part Nos. F148412, F148414, F148014, and F148560.
(
s
)
Plastic syringes
.—B&D 3 mL, or equivalent.
(
t
)
Syringe filters
.—PTFE 0.2 µm, Acrodisc 13 mm, Part
No. 28143-930, or equivalent.
(
u
)
Autosampler vials
.—Glass, 2 mL, 12 × 32 mmwith screw
neck (PTFE pre-split septa caps). Waters (Cat. No. 186000847C;
http://www.waters.com), or equivalent.
(
v
)
Vial inserts
.—300 µL (Waters; Cat. No. WAT094170).
(
w
)
Chromatography equipment and supplies.—
(
1
)
Mass
spectrometer
.—Waters Xevo TQ-S tandem quadrupole, or
equivalent.
(
2
)
Liquid chromatograph
.—Waters Acquity UPLC, or
equivalent.
(
3
)
LC column
.—Waters Acquity UPLC
®
BEH C
18
, 1.8 µm,
2.1 × 100 mm (Part No. 186002352).
C. Reagents
(
a
)
Sodium fluoroacetate 99.3%
.—Fluka PESTANAL (Cat.
No. 31220-100MG; Sigma-Aldrich).
(
b
)
13
C
2
,
2
H
2
-fluoroacetate
.—Cambridge
Isotope
Laboratories (Cat. No. CDLM-7943-0;
http://www.isotope.com).
(
c
)
Acetonitrile
.—Fisher Scientific Optima LC/MS grade
(Cat. No. L-1693).
(
d
)
Ethyl acetate
.—Fluka LC/MS Chromasolv (Cat.
No. 34972-R).
(
e
)
Ethanol
.—ACS reagent grade (≥99.5%; Sigma-Aldrich,
Cat. No. 459844).
(
f
)
Hydrochloric acid
.—Trace metal grade (Fisher Scientific,
Cat. No. A508-P500).
(
g
)
Pyridine
.—Sigma-Aldrich (Cat. No. 270970).
(
h
)
Ammonium acetate.—
Fluka (Cat. No. 73594).
(
i
)
2
-
NPH 97%
.—Sigma-Aldrich (Cat. No. N21588).
(
j
)
EDC
.—Sigma-Aldrich (Cat. No. 03449).
(
k
)
Laboratory water
.—18 MΩ-cm.
D. Solutions
(
a
)
Monofluoroacetate stock standard
.—Approximately
1000 µg/mL in water.
(
1
) Weigh 13.0 ± 1.0 mg sodium fluoroacetate, record weight
(
m
) to the nearest 0.1 mg, and transfer to a 10 mL volumetric
flask.
(
2
) Dissolve in 4–5 mL laboratory water, dilute to volume
with laboratory water, and mix thoroughly.
Store at room temperature. Expiration 6 months.
(
3
) Calculate exact concentration
C
(µg/mL) =
m
× 0.993
× 100 × 0.780 where
m
= amount weighed (mg), 0.993 = purity,
and 0.78 = conversion factor from sodium salt to free acid.
(
b
)
Monofluoroacetate working standard
.—8 µg/mL in
acetonitrile–water (60 + 40, v/v).
(
1
) Calculate volume of stock standard to be used
V
(µL) =
10 × 1000 × 8/
C
.
(
2
) Transfer
V
μL monofluoroacetate stock standard to a
10 mL volumetric flask.
(
3
) Bring to volume with acetonitrile–water (60 + 40, v/v).
Expiration 6 months.
(
c
)
Monofluoroacetate working standard
(
1 + 10)
.—0.8 µg/
mL in acetonitrile–water (60 + 40, v/v).
(
1
) Transfer 100 µL monofluoroacetate working standard,
8 µg/mL, to 2 mL autosampler vial.
(
2
) Add 900 µL acetonitrile–water (60 + 40, v/v) and mix
well. Expiration 6 months.
(
d
)
Internal standard stock solution
.—Approximately
100 μg/mL in water.
(
1
) Transfer the contents of the
13
C
2
,
2
H
2
-fluoroacetate
ampoule (~10 mg) to a 100 mL volumetric flask.
(
2
) Rinse the ampoule three times with laboratory water and
transfer each rinse to the volumetric flask.
(
3
) Bring to volume and mix well. Expiration 6 months.
(
e
)
Internal standard working solution.—
Approximately
2.0 μg/mL in acetonitrile–water (60 + 40, v/v).
(
1
) Transfer 20 μL internal standard stock solution to 2 mL
autosampler vial.
(
2
) Add 980 μL acetonitrile–water (60 + 40, v/v) and mix
well.
(
3
) Scale proportionally as needed for the worklist.
Expiration 1 day.
(
f
)
QC1 overspike solution
.—0.5 µg/mL monofluoroacetate
in water.
(
1
) Calculate volume of stock standard to be used
V
(µL) =
10 × 1000 × 0.5/
C
.
(
2
) Transfer
V
μL monofluoroacetate stock standard to a
10 mL volumetric flask.
(
3
) Add water to the 10 mL mark and mix well.
(
g
)
QC2 overspike solution
.—10 µg/mL monofluoroacetate
in water.
(
1
) Calculate volume of stock standard to be used
V
(µL) =
10 × 1000 × 10/
C
.
(
2
) Transfer
V
μL monofluoroacetate stock standard to a
10 mL volumetric flask.
(
3
) Add water to the 10 mL mark and mix well.
(
h
)
Acetonitrile–water (60 + 40, v/v)
.
(
1
) Transfer 60 mL acetonitrile to 100 mL glass bottle.
(
2
) Add 40 mL water and mix well.
(
i
)
Acetonitrile–water (25 + 75, v/v)
.
(
1
) Transfer 25 mL acetonitrile to 100 mL glass bottle.
(
2
) Add 75 mL water and mix well.
(
j
)
0.1 N HCl–ethanol (50 + 50, v/v).
(
1
) Transfer 0.5 mL hydrochloric acid to 100 mL glass bottle.
(
2
) Add 50 mL water.
Candidates for 2016 Method of the Year
52