29 / 363
Joseph et al.:
J
ournal of
AOAC I
nternational
V
ol.
98, N
o
. 3, 2015
1123
the pellets have dissolved, allow the solution to cool and then
transfer quantitatively through a glass funnel into a 2000 mL
measuring cylinder and bring to volume with deionized water.
Store at room temperature.
(
d
)
20 mg/mL 3-nitroaniline (100 mL)
.—(
Caution
: Wear
gloves when working with this chemical.) Weigh 2.0 g aliquots
of 3-nitroaniline into 100 mL Schott bottles and cap tightly.
Store at room temperature.
To one preweighed bottle of 3-nitroaniline add 100 mL
acetonitrile using a graduated measuring cylinder. This is
sufficient for two batches of 36 sample tubes. Prepare fresh
daily.
(e)
100 mg/mL EDAC (25 mL)
.—(
Caution
: Exposure to
moisture degrades this reagent.) Preweigh 2.5 g aliquots of
EDAC into 50 mL polypropylene tubes and cap tightly. Store in
a freezer at or below –10°C in a desiccated container.
To one preweighed tube of EDAC add 25 mL deionized
water. Prepare fresh daily.
(
f
)
TBME–n-hexane (70 + 30, v/v; 2000 mL)
.—Measure
1400 mL TBME into a 2000 mL Schott bottle and add 600 mL
n
-hexane. Cap and mix. Store at room temperature.
(
g
)
Sulfuric acid in water (25%, v/v; 2000 mL)
.—(
Caution
:
Preparation of solution should be performed inside a fume
cupboard.) Add approximately 1200 mL deionized water to a 2
L volumetric flask followed by slow addition of 500 mL sulfuric
acid. Mix and allow to cool to room temperature. Bring to 2 L
volume and store in a Schott bottle. Store at room temperature.
(
h
)
0.05 M potassium dihydrogen phosphate, pH 2.3
(1000 mL)
.—Weigh 6.80 g potassium dihydrogen phosphate
into a 500 mL beaker. Add 300 mL deionized water to dissolve
the potassium dihydrogen phosphate and quantitatively transfer
into a 1 L Schott bottle. Add a further 300 mL deionized water
to the beaker to dissolve any remaining potassium dihydrogen
phosphate, quantitatively transfer into the Schott bottle, make
up to 1 L. Cap, mix, and adjust the pH to 2.3 ± 0.1 with
concentrated phosphoric acid. Store at room temperature.
(
i
)
0.1 M sodium hydrogen carbonate (1000 mL)
.—Weigh
8.40 g sodium hydrogen carbonate into a 500 mL beaker. Add
300 mL deionized water to dissolve the sodium hydrogen
carbonate and quantitatively transfer into a 1 L Schott bottle.
Add a further 300 mL deionized water to the beaker to dissolve
any remaining sodium hydrogen carbonate, quantitatively
transfer into the Schott bottle, make up to 1 L, cap, and mix to
ensure full solubility. Store at room temperature.
(
j
)
AG 1-X8 anion exchange resin
.—Before use, soak the
AG 1-X8 anion exchange resin in deionized water for 18–24 h,
and store in deionized water until use. Store in a refrigerator.
(
k
)
HPLC mobile phase A:
10 mM ammonium acetate in
water (1000 mL)
.—Weigh 0.77 g ammonium acetate into a 1 L
Schott bottle, followed by 1000 mL deionized water. Cap and
mix to ensure full solubility. Store at room temperature.
(
l
)
HPLC mobile phase B: 10 mM ammonium acetate in 97%
acetonitrile (1000 mL)
.—Weigh 0.77 g ammonium acetate into
a 50 mL beaker. Use 30 mL deionized water to quantitatively
transfer to a 1 L Schott bottle. Stir to fully dissolve and add
970 mL acetonitrile. Sonicate for 10 min to ensure full solubility.
Store at room temperature.
Figure 2015.02B. Chromatograms of confirmation ion for recovery 1 (matrix blank; top), recovery 2 (0.1 µg/kg, ≈LOQ;
middle), and recovery 4 (1.0 µg/kg, LOR; bottom).
Candidates for 2016 Method of the Year
28