2014 ERP New Member Book

AOACO FFICIAL M ETHODS OF A NALYSIS (2012)

G UIDELINES FOR S TANDARD M ETHOD P ERFORMANCE R EQUIREMENTS Appendix F, p. 9

Table A4. Expectedprecision (repeatability) as a functionof analyteconcentration a Analyte,% Analyte ratio Unit RSD,% 100 1 100% 1.3 10 10 –1 10% 1.9 1 10 –2 1% 2.7 0.01 10 –3 0.1% 3.7 0.001 10 –4 100 ppm (mg/kg) 5.3 0.0001 10 –5 10 ppm (mg/kg) 7.3 0.00001 10 –6 1ppm (mg/kg) 11 0.000001 10 –7 100 ppb (μg/kg) 15 0.0000001 10 –8 10 ppb (μg/kg) 21 0.00000001 10 –9 1 ppb (μg/kg) 30 a Table excerpted from AOACPeer-VerifiedMethodsProgram, Manual on Policies andProcedures (1998)AOAC INTERNATIONAL, Gaithersburg, MD. The precision of amethod is the closeness of agreement between independent test results obtained under stipulated conditions. Precision is usually expressed in terms of imprecision and computed as a relative standard deviation of the test results. The imprecision of amethod increases as the concentration of the analyte decreases. This table provides targetsRSDs for a range of analyte concentrations.

Table A5. Expected recovery as a functionof analyte concentration a Analyte,% Analyte ratio Unit

Mean recovery,%

100

1

100%

98–102 98–102 97–103 95–105 80–110 80–110 80–110 60–115

10

10 –1 10 –2 10 –3 10 –4 10 –5 10 –6 10 –7 10 –8 10 –9

10%

1

1%

0.01

0.1%

0.001

100 ppm 90–107

0.0001 0.00001 0.000001 0.0000001 0.00000001

10 ppm

1 ppm

100 ppb 10 ppb

1 ppb 40–120 a Table excerpted from AOACPeer-VerifiedMethodsProgram, Manual on Policies andProcedures (1998)AOAC INTERNATIONAL, Gaithersburg, MD. Recovery is definedas the ratio of theobservedmean test result to the true value. The rangeof theacceptablemean recovery expands as the concentration of theanalytedecreases. This tableprovides target mean recovery ranges for analyte concentrations from 100% to 1ppb. Table A6. Predicted relative standarddeviationof reproducibility (PRSD R ) a Concentration (C) Mass fraction (C) PRSD R ,% 100% 1.0 2 1% 0.01 4 0.01% 0.0001 8 1 ppm 0.000001 16 10 ppb 0.00000001 32 1 ppb 0.000000001 45 a Table excerpted from Definitions andCalculations of HorRat Values from IntralaboratoryData , HorRat for SLV.doc, 2004-01-18,AOAC INTERNATIONAL, Gaithersburg, MD. Predicted relative standarddeviation=PRSD R . Reproducibility relative standarddeviation calculated from theHorwitz formula: PRSD R = 2C –0.15 , whereC is expressed as amass fraction This tableprovides the calculatedPRSD R for a range of concentrations. SeeAnnexD for additional information.

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