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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

241