AOAC OMA# 2011.14 (Final Action Review)-OMB

Table 2011.14B. Interlaboratory study results for copper Matrix Mean, mg/kg Rec., % S r a

RSD r

b , % S

R c , ng/g RSD R

d , % HorRat

No. of labs e Outlier labs f

Chocolate milk powder Dietetic milk powder 2

5.92 6.19 2.01

NA h 101

0.09 0.19

1.57 3.06 4.98 3.84

0.29 0.38 0.24 0.35

4.97 6.12

0.41 0.50 0.81 0.56

9 9 9 9

NS g

NS NS NS

Infant cereal

NA 0.10

11.72

Peanut butter NIST SRM 2387

4.98 (4.93) i 5.64 (5.94) i

101

0.19

7.08

Wheat gluten NIST RM 8418

95

0.13

2.27

0.27

4.77

0.39

9

NS

a S r = Standard deviation for repeatability (within laboratory). b RSD r = Relative standard deviation for repeatability. c S R = Standard deviation for reproducibility (among laboratories). d RSD R = Relative standard deviation for reproducibility. e Reporting laboratories minus outliers. f C = Cochran outlier; SG = Single Grubbs outlier; DG = Double Grubbs outlier.

g NS = Not significant. h NA = Not available. i Value in parentheses = Certified or reference values.

Predigest for at least 10 min at room temperature or until vigorous foaming subsides. Close MDC vessels and distribute onto microwave carousel to ensure uniform microwave power application on all samples. ( 3 ) Food-grade salt sample preparation .—Weigh 0.20 ± 0.01 g food-grade salt into a 100 mL volumetric flask. Add deionized water and 10 mL HNO 3 . Dissolve salt and dilute to volume with deionized water. ( b ) Test portion digestion .—[ Caution : Application of microwave digestion systems involves hot pressurized acid solutions and concentrated acids. Use fume hood and wear full personal laboratory protective clothing, gloves and appropriate eye protection (safety glasses) when using glassware and preparing standards or samples with acid solutions. Follow manufacturer’s directions for safety risk and safety environment of microwave

systems. Never remove hot vessels from microwave; wait until they are near room temperature. Keep microwave door closed while vessels are hot. The door is the primary safety device if a vessel vents.] ( 1 ) Sample digestion.— With power setting appropriate to MDC (maximum power of 1600 W) and MDO models (maximum power of 600 W), and number of vessels used, heat MDO vessels at 200 ± 20°C for 20 min or ramp MDC temperature from ambient to 200 ± 20°C in 15 min and hold at 200°C for 25 min. ( Note: Yellow vapors will be emitted during the hydrolysis in MDO vessels.) Carefully remove the MDO vessels. Allow the vessels to cool down to room temperature. Add 5 mL HCl 35% (w/v) into MDO vessels and heat MDO vessels at 200 ± 20°C for 20 min.

Table 2011.14C. Interlaboratory study results for iron Matrix Mean, mg/kg Rec., % S r a

RSD r

b , % S

R c , ng/g RSD R

d , % HorRat

No. of labs e Outlier labs f

Chocolate milk powder Dietetic milk powder 2

164.77

97

6.72 2.51 1.36 0.65

4.08 0.02 1.81 4.17

11.25

6.83 5.56 4.42

0.92 0.68 0.53 1.18

9 9 9 8

NS g

83.11 75.18

102

4.62 3.32 1.95

NS NS 6C

Infant cereal

94 95

Peanut butter NIST SRM 2387 15.65 (16.4) h

12.45

Wheat gluten NIST RM 8418

49.29 (54.3) h

91

0.93

1.89

1.54

3.12

0.35

8

2C

a S r = Standard deviation for repeatability (within laboratory). b RSD r = Relative standard deviation for repeatability. c S R = Standard deviation for reproducibility (among laboratories). d RSD R = Relative standard deviation for reproducibility. e Reporting laboratories minus outliers. f C = Cochran outlier; SG = Single Grubbs outlier; DG = Double Grubbs outlier. g NS = Not significant. h Value in parentheses = Certified or reference values.

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