SPDS eBook March 2017

AOAC O FFICIAL M ETHODS OF A NALYSIS (2012)

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

Table A4. Expected precision (repeatability) as a function of analyte concentration a

Table A5. Expected recovery as a function of analyte concentration a

Analyte, % Analyte ratio

Unit

RSD, %

Analyte, % Analyte ratio

Unit

Mean recovery, %

100

1

100%

1.3

100

1

100%

98–102

10 –1

10 –1

10

10%

1.9

10

10%

98–102

10 –2

10 –2

1

1%

2.7

1

1%

97–103

10 –3

10 –3

0.01

0.01

0.1%

3.7

0.1%

95–105

10 –4

10 –4

0.001

100 ppm (mg/kg)

5.3

0.001

100 ppm 90–107

10 –5

10 –5

0.0001

10 ppm (mg/kg)

7.3

0.0001

10 ppm

80–110

10 –6

10 –6

0.00001

1 ppm (mg/kg)

11

0.00001

1 ppm

80–110

100 ppb ( μ g/kg) 10 ppb ( μ g/kg) 1 ppb ( μ g/kg)

10 –7

10 –7

0.000001

15

0.000001

100 ppb

80–110

10 –8

10 –8

0.0000001

0.0000001

21

10 ppb

60–115

0.00000001 30 a Table excerpted from AOAC Peer-Verified Methods Program, Manual on Policies and Procedures (1998) AOAC INTERNATIONAL, Gaithersburg, MD. The precision of a method 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 a method increases as the concentration of the analyte decreases. This table provides targets RSDs for a range of analyte concentrations. 10 –9

0.00000001 40–120 a Table excerpted from AOAC Peer-Verified Methods Program, Manual on Policies and Procedures (1998) AOAC INTERNATIONAL, Gaithersburg, MD. Recovery is defined as the ratio of the observed mean test result to the true value. The range of the acceptable mean recovery expands as the concentration of the analyte decreases. This table provides target mean recovery ranges for analyte concentrations from 100% to 1 ppb. 10 –9 1 ppb

Table A6. Predicted relative standard deviation of 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 45 a Table excerpted from Definitions and Calculations of HorRat Values from Intralaboratory Data , HorRat for SLV.doc, 2004-01-18, AOAC INTERNATIONAL, Gaithersburg, MD. 0.000000001

. Reproducibility relative

Predicted relative standard deviation = PRSD R standard deviation calculated from the Horwitz formula:

R = 2C –0.15 , where C is expressed as a mass fraction

PRSD

for a range of concentrations.

This table provides the calculated PRSD R See Annex D for additional information.

© 2012 AOAC INTERNATIONAL