28 / 363
1122
Joseph et al.
: J
ournal of
AOAC I
nternational
Vol. 98, No. 3, 2015
(
i
)
Laboratory glassware
.—Measuring cylinders, volumetric
flasks, and beakers.
(
j
)
Multi-step dispenser with appropriate tips
.—Eppendorf
Stream or equivalent.
(
k
)
Nitrogen blow-down
.—Capable of maintaining a
temperature 40 ± 10°C.
(
l
)
pH meter
.
(
m
)
Polypropylene SPE reservoirs
.—10 mL, with adapters.
(
n
)
Positive displacement pipets
.—25, 100, 250, and 1000
µL, with tips.
(
o
)
Refrigerator and freezer.
(
p
)
Resin chromatography column
.—10 mL polypropylene
(Bio-Rad).
(
q
)
Shaker
.—Reciprocating bench top.
(
r
)
Ultrasonic bath
.
(
s
)
Vacuum manifold for SPE cartridges.—
With stopcocks.
(
t
)
Vortex mixer
.
(
u
)
Water bath.—
Maintained at 40 ± 2°C.
Analytical instrumentation
.—
(
v
)
LC-MS/MS instrument
.—ABSciex 5500 QTRAP
coupled with Agilent 1290 Series HPLC.
(
w
)
HPLC guard column
.—Phenomenex Security C18,
4 × 2 mm.
(
x
)
HPLC column
.—Agilent XDB-C18 100 × 4.6 mm, 1.8
μm.
C. Reagents
All reagents and chemicals must be of such a grade that they
do not interfere with the analytical process.
Chemicals
.—
(
a
)
Acetone
.—Pesticide grade.
(
b
)
Acetonitrile.—
Pesticide grade.
(
c
)
AG 1-X8 resin
.—100–200 mesh chloride form, ACS
reagent grade.
(
d
)
Ammonium acetate
.—ACS reagent grade.
(
e
)
Deionized water.—
Laboratory purified, ≥18 ΩM.
(
f
)
Hydrochloric acid
.—Concentrated, ACS reagent grade;
37–38%.
(
g
)
Methanol.—
Pesticide grade.
(
h
)
n
-
Hexane
.—Pesticide grade.
(
i
)
Phosphoric acid
.—Concentrated, ACS reagent grade.
(
j
)
Potassium dihydrogen phosphate
.—ACS reagent grade.
(
k
)
Potassium hydroxide.—
ACS reagent grade.
(
l
)
Sodium sulfate, anhydrous
.—ACS reagent grade.
(
m
)
Sodium hydrogen carbonate
.—ACS reagent grade.
(
n
)
Sulfuric acid
.—Concentrated, ACS reagent grade.
(
o
)
TBME
.—Pesticide grade.
(
p
)
1-Ethyl-3-(3-dimethylaminopropyl)
carbodiimide
hydrochloride (EDAC)
.—ACS reagent grade.
(
q
)
3-Nitroaniline
.—ACS reagent grade.
Solutions.—
(
a
)
5Mhydrochloric acid (2000mL)
.—(
Caution
: Preparation
of solution should be performed inside a fume cupboard.) Into a
2000 mL volumetric flask add 800 mL deionized water. To this
add 832 mL of 37–38% (12 M) concentrated hydrochloric acid.
Mix and allow to cool. Bring to volume with deionized water.
Store at room temperature.
(
b
)
0.2 M hydrochloric acid (2000 mL)
.—Into a 2000 mL
volumetric flask add 800 mL deionized water. To this add 80 mL
of 5 M hydrochloric acid. Mix and allow to cool, and bring to
volume with deionized water. Store at room temperature.
(
c
)
2 M potassium hydroxide (2000 mL)
.—(
Caution
:
Preparation of solution should be performed inside a fume
cupboard.) Place 1600 mL deionized water in a 2000 mL beaker
and place on a magnetic stirrer with follower. Weigh 224.4 g
potassium hydroxide into a 500 mL beaker. Add the potassium
hydroxide, a few pellets at a time, to the stirred solution. Do not
allow the temperature to rise above warm to the touch. When all
Table 2015.02A. Fortification of recovery samples
Tube No.
Name
Volume, µL
Concn
fluoroacetic
acid, µg/kg
WS3 WS2 WS3
1
a
Matrix standard 0
a
0
a
0
a
5
a
2
Recovery 1 0 0 40
0
3
Recovery 2 25 0 40
0.1
4
Recovery 3 125 0 40
0.5
5
Recovery 4 0 25 40
1
6
Recovery 5 0 125 40
5
7
Reagent blank 0 0 40
0
a
The matrix standard is fortified at step
F
(
b
)(
9
).
Figure 2015.02A. Sodium fluoroacetate.
Table 2015.02B. Identification parameters for compounds analyzed as negative ions
Compound (3-nitroaniline
derivatives of analyte and
internal standard)
Expected retention
time, min Molecular ion (Q1) Product ion (Q3) Dwell, ms DP, V CE, eV CXP, V
2-Fluoro-3
′
-
nitroacetanilide
2.06
196.931
122.000
50
–120
–24
–17
196.931
146.900
50
–120
–22
–23
196.931
117.800
50
–120
–28
–17
1,2-
13
C-2,2-D-2-fluoro-3
ʹ
-
nitroacetanilide
2.06
201.001
134.900
50
–115
–30
–21
201.001
45.900
50
–115
–22
–23
Candidates for 2016 Method of the Year
27