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1126 

Joseph et al.

: J

ournal of

AOAC I

nternational

Vol. 98, No. 3, 2015

(

26

) Decant the supernatant into a clean 15 mL tapered,

polypropylene tube.

(

27

) Evaporate the solvent to incipient dryness under

nitrogen at 40 ± 10°C.

Note

: Do not leave on heating block as excess heating may

degrade derivatized analyte.

(

28

) Allow tubes to return to near room temperature and then

redissolve residue in 150 µL acetonitrile.

(

29

) Vortex mix at low speed.

(

30

) Centrifuge at 2400 ×

g

RCF for 1 min.

(

31

) Transfer clear solvent layer to a tapered insert in an

autosampler vial, making sure not to transfer any solid and/or

particulate matter. Cap firmly.

Note

: Final extracts have been shown to be stable at least

5 days when stored in the freezer at –10°C or below.

(

c

) 

Instrumental

determination

.—(

1

) 

Identification

parameters

.—Identification parameters for the analysis of

sodium fluoroacetic acid are given in Table

2015.02B

.

(

2

) 

Analytical

instrumentation

.—(

a

)

 General

.—Agilent

1290 HPLC system coupled with a 5500 QTRAP Triple Quad

Mass Spectrometer. The system is controlled by ABSciex

Analyst software. Peak integration is handled with ABSciex

MultiQuant Analysis software.

Note

:

See

Figure

2015.02B

for exemplary chromatograms.

(

b

) 

LC parameters

.—

See

Table

2015.02C

for HPLC solvent

gradient.

(

i

) 

Column

.—Agilent XDB-C18 100 × 4.6 mm.

(

ii

) 

Guard column

.—Phenomenex Security C18, 4 × 2 mm.

(

c

) 

Mass spectrometer parameters

.—

See

Table

2015.02D

for full analytical parameters.

G. Calculations

Quantification of fluoroacetic acid is based on peak area.

Matrix recoveries are used to generate calibration curves. An

unknown peak that falls within the evaluation window (as

calculated by recoveries and internal standard) is quantified

from the appropriate calibration curve and the value tabulated,

together with peak identification information. Each potential

unknown is then manually assessed for the quality of

identification by viewing integrated chromatograms and those

of any qualifying ions.

C

u

=

RR

/

Sl

where

C

u

= concentration of unknown sample in µg/kg;

RR

=

relative response of unknown sample;

Sl

= slope of calibration

curve.

H. Method Performance and Quality Control

(

a

) 

Reagent blank test

.—A reagent blank (deionized water)

test is performed with each batch.

(

b

) 

Matrix standard test

.—Performed with each batch

according to Table

2015.02A

.

(

c

) 

Matrix blank test (Recovery 1)

.—A matrix blank test is

performed with each batch.

(

d

) 

Matrix recovery test (recovery samples)

.—Performed

with each batch according to Table

2015.02A

.

(

e

) 

Certified reference materials (CRM)

.—No CRM is

currently available. In practice, external checks of the method

are performed by participation in interlaboratory calibration

studies when available.

(

f

) 

Performance values

.—Values found in Table

2015.02E

are calculated from the in-house single-laboratory validation

(SLV)completed by AsureQuality Ltd.

(

g

) 

Acceptance criteria

.—(

1

) 

Individual sample acceptance

criteria

.—The internal standard response for an individual

sample should exceed 33% of the mean internal standard

response of the recovery samples.

(

2

) 

Batch acceptance criteria

.—Analyte relative recoveries

for the recovery samples should be within 3 SD of the mean

relative recovery established from control charts. Calibration

curves should have a coefficient of determination R

> 0.95.

(

3

) 

Positive sample acceptance criteria

.—Retention time

acceptance criteria are given in Table

2015.02F

. Ion ratio

acceptance limits are given in Table

2015.02G

.

(

h

) 

Control charts

.—Control charts are to be maintained

for the method by plotting the relative recovery of the matrix

standard quantified from the slope of the recovery curve.

References

 (1) New Zealand (Maximum Residue Limits of Agricultural

Compounds) Food Standards 2015 (February 20, 2015)

NZ

Gazette

18

 (2) 

Off. J. Eur. Commun

.

L221

,

8(2002)

 (3) AOAC SMPR 2015.001

J. AOAC Int

. (future issue)

Table 2015.02G.  Ion ratios and limits of acceptance

Compound (3-nitroaniline derivative of analyte)

Transitions

MRM ratio

a

Acceptance limit, %

b

2-Fluoro-3

ʹ

-nitroacetanilide

196.9 → 146.9/196.9 → 122.0

1.01

±20

196.9 → 117.8/196.9 → 122.0

0.75

±20

a

 Representative MRM ratio. These values are indicative and should be measured for each individual batch.

b

See

reference 2.

Candidates for 2016 Method of the Year

31