AOAC RI Chemical Cont. Methods-2018 Awards

M astovska et al .: J ournal of AOAC I nternational V ol . 98, N o . 2, 2015  485

Table 2014.08C. ( continued )

No. of laboratories

No. of replicates

Mean concn, µg/kg

Mean recovery, % s r

PAH

, µg/kg s R

, µg/kg RSD r

, % RSD R

, % HorRat

10

20 18 20 16 16 16 16 20 20 20

17.9 23.7

89.3 94.6 84.7 91.7 96.8 93.1 91.9 94.6 95.4 93.2

0.9 1.9

1.6 4.0

4.9 8.1 9.5 4.9 5.3 4.1 3.6 5.0 4.0 3.8

8.8

0.30 0.61 1.12 0.61 0.20 0.40 0.38 0.31 0.41 0.37

Naph

9

17.1 25.2 13.1

10

105.9 146.7

10.1

26.7 19.2

8 8 8 8

7.2 0.8 3.9 5.8 0.7 2.9 4.5

Phe

14.5 93.1

0.9 8.5

6.1 9.2 8.1 9.3 9.8 8.3

160.8

13.0

Pyr

10 10 10

14.2 71.5

1.3 7.0 9.6

116.5

evaporation technique (e.g., small round-bottom flasks, suitable tubes, or glassware for Kuderna-Danish evaporation). It is recommended to heat the glassware for at least 2 h at 250°C to remove potential contamination. D. Reference Standards ( a )  PAH standards.— High-purity reference standards of the PAHanalytes (1,7-dimethylphenanthrene, 1-methylnaphthalene, 1-methylphenanthrene, 2,6-dimethylnaphthalene, 3-methyl- chrysene, anthracene, benz[ a ]anthracene, benzo[ a ]pyrene, benzo[ b ]fluoranthene, benzo[ g,h,i ]perylene, benzo[ k ] fluoranthene, chrysene, dibenz[ a,h ]anthracene, fluoranthene, fluorene, indeno[1,2,3- cd ]pyrene, naphthalene, phenanthrene, and pyrene). ( b )  U.S. Environmental Protection Agency (EPA) 16 PAH cocktail.— ( 13 C, 99%), Product No. ES-4087 (5 µg/mL, 1.2 mL in nonane), Cambridge Isotope Labs ( Tewksbury, MA, USA ) or equivalent. Containing: Acenaphthene ( 13 C 6 , 99%), acenaphthylene ( 13 C 6 , 99%), anthracene ( 13 C 6 , 99%), benz[ a ]anthracene ( 13 C 6 , 99%), benzo[ b ]fluoranthene ( 13 C 6 , 99%), benzo[ k ]fluoranthene ( 13 C 6 , 99%), benzo[ g,h,i ]perylene ( 13 C 12 , 99%), benzo[ a ]pyrene ( 13 C 4 , 99%), chrysene ( 13 C 6 , 99%), dibenz[ a,h ]anthracene ( 13 C 6 , 99%), fluoranthene ( 13 C 6 , 99%), fluorene ( 13 C 6 , 99%), indeno[1,2,3- cd ]pyrene ( 13 C 6 , 99%), naphthalene ( 13 C 6 , 99%), phenanthrene ( 13 C 6 , 99%), and pyrene ( 13 C 6 , 99%). E. Preparation of Standard Solutions ( a )  Individual stock solutions.— Prepare individual PAH stock solutions at approximately 1000 or 2500 µg/mL in toluene. ( b )  Mixed stock standard solution.— Use analyte individual stock solutions to obtain a mixed solution of each PAH at 10 µg/mL (for benzo[ a ]pyrene) and other low-level PAHs) or 25 µg/mL (for chrysene and other higher-level PAHs) or 50 µg/mL (for naphthalene) in isooctane. See Table 2014.08E for analyte concentrations in the mixed stock standard solution. ( c )  Working PAH Solution A.— Accurately transfer 0.5 mL of the mixed stock standard solution into a 5 mL volumetric flask and dilute to volume with isooctane. ( d )  Working PAH Solution B.— Accurately transfer 0.5 mL of

the Working PAH Solution A into a 5 mL volumetric flask and dilute to volume with isooctane. ( e )  Internal standard solution.— Prepare 1 µg/mL solution of 13 C-PAHs in isooctane by 5-fold dilution of the 5 µg/mL EPA16 13 C-PAHs cocktail with isooctane. ( f )  Calibration standard solutions— Prepare eight levels of calibration standard solutions (1 mL each) in 2 mL amber screw-cap vials. It is recommended to distribute small portions (enough for a single injection) of the calibration standard solutions into multiple crimp-top vials with 100 µL deactivated glass inserts. See Table 2014.08A for analyte concentrations in the calibration standards and Table 2014.08F for the dilution scheme. ( 1 )  For level 1 calibration standard .–Accurately transfer 50 µL of the Working PAH Solution B into the vial and add 50 µL of the 1 µg/mL 13 C-PAHs solution and 900 µL isooctane. Cap the vial and vortex mix briefly. ( 2 )  For level 2 calibration standard .–Accurately transfer 100 µL of the Working PAH Solution B into the vial and add 50 µL of the 1 µg/mL 13 C-PAHs solution and 850 µL isooctane. Cap the vial and vortex mix briefly. ( 3 )  For level 3 calibration standard .–Accurately transfer 200 µL of the Working PAH Solution B into the vial and add 50 µL of the 1 µg/mL 13 C-PAHs solution and 750 µL isooctane. Cap the vial and vortex mix briefly. ( 4 )  For level 4 calibration standard .–Accurately transfer 500 µL of the Working PAH Solution B into the vial and add 50 µL of the 1 µg/mL 13 C-PAHs solution and 450 µL isooctane. Cap the vial and vortex mix briefly. ( 5 )  For level 5 calibration standard .–Accurately transfer 100 µL of the Working PAH Solution A into the vial and add 50 µL of the 1 µg/mL 13 C-PAHs solution and 850 µL isooctane. Cap the vial and vortex mix briefly. ( 6 )  For level 6 calibration standard .–Accurately transfer 200 µL of the Working PAH Solution A into the vial and add 50 µL of the 1 µg/mL 13 C-PAHs solution and 750 µL isooctane. Cap the vial and vortex mix briefly. ( 7 )  For level 7 calibration standard .–Accurately transfer 500 µL of the Working PAH Solution A into the vial and add 50 µL of the 1 µg/mL 13 C-PAHs solution and 450 µL isooctane. Cap the vial and vortex mix briefly. ( 8 )  For level 8 calibration standard .–Accurately transfer 100 µL of the mixed stock standard solution into the vial and