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© 2015 AOAC INTERNATIONAL
(
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.
Table 2015.04B. Instrumental conditions
Chromatography
Flow rate
300 µL/min
Column temperature
40
°
C
Injection volume
10 μL
Sample temperature
Ambient
Gradient program
Time
% A
% B
Curve
0.00
90
10
6
1.00
90
10
6
7.00
45
55
6
9.00
0
100
6
9.01
90
10
6
12.00
90
10
6
MS tune
Ionization mode
ESI-
Cone gas
250 L/h
Capillary
0.5 kV
Nebulizer
7.0 bar
Source offset
20.0 V
Collision gas flow
0.15 mL/min
Source temperature
150
°
C
Quad 1 resolution
Unit mass (0.75 Da FWHM)
Gas temperature
350
°
C
Quad 2 resolution
Unit mass (0.75 Da FWHM)
Desolvation gas flow
900 L/h
MS calibration range
50–2000 amu
MS/MS transitions
Compound
Parent mass,
m/z
Daughter mass,
m/z
Dwell, s
Cone (V)
Collision energy , V
MFA-2NPH
212
182
0.15
20
15
MFA-2NPH_IS
216
186
0.15
20
15
Table 2015.04C. Processing method
Quantitation trace
212 > 182 Smoothing iterations
2
Internal standard trace 216 > 186
Smoothing width
2
Response type
Ratio to IS Polynomial type
Linear
Predicted RT
a
4.0 min
Origin
Excluded
RT window
±0.2 min
Weighting
1/X
a
RT = Retention time.
Candidates for 2016 Method of the Year
48