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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.

255