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1126  Joseph et al. : J ournal of AOAC I nternational Vol. 98, No. 3, 2015

Table 2015.02G.  Ion ratios and limits of acceptance Compound (3-nitroaniline derivative of analyte)

MRM ratio a

Acceptance limit, % b

Transitions

2-Fluoro-3 ʹ -nitroacetanilide

196.9 → 146.9/196.9 → 122.0 196.9 → 117.8/196.9 → 122.0

1.01 0.75

±20 ±20

a  Representative MRM ratio. These values are indicative and should be measured for each individual batch. b See reference 2.

( 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 2  > 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)