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© 2015 AOAC INTERNATIONAL
(
e
)
Formic acid.—
88%, ACS.
(
f
)
Laboratory water.—≥
15 MΩ·cm
.
(
g
)
Potassium cyanide. .—≥
97%, ACS.
(
h
)
Riboflavin.—≥
96%, ACS.
(
i
)
Sodium acetate anhydrous or sodium acetate trihydrate
.—
ACS.
(
j
)
Taka-diastase.—
Accurate
Chemical
Co.
(www.
accuratechemical.com) or equivalent.
(
k
)
Triethylamine (TEA).—
HPLC grade.
(
l
)
Vitamin B
12
(cyanocobalamin) standard.—
USP reference,
official lot number (refer to USP catalog for current lot). Store in
desiccator protected from white light. (
Note
:
See
standard label for
purity.)
D. Solution and Standard Preparation
All solutions can be scaled up or down for convenience provided
good laboratory practices are observed. Solutions can be stored at
2–30°C in tight, inert containers unless otherwise noted.
(
a
)
Solutions.—
(
1
)
Mobile phase A.—
4.0 mL TEA diluted
with 1000 mL water and pH adjusted to 5–7 with about 1.25 mL
concentrated formic acid. Expiration 1 week.
Table 2011.10B. Single-laboratory validation: Accuracy (spike recovery) data for vitamin B
12
Sample type
No. of replicates
(duplicates on multiple days)
Native level
(µg/100 g RTF)
Recovery, %
RSD, %
Infant formula (NIST SRM 1849a)
4
42.6
a
95.7
5.32
Infant formula powder soy-based
6
0.404
98.2
5.32
Infant formula powder milk-based
4
0.236
104
4.32
Infant formula RTF milk-based
6
0.326
96.4
8.17
Infant formula powder partial hydrolyzed
milk-based
4
0.347
98.2
6.34
Infant formula powder partial hydrolyzed
soy-based
6
0.248
95.7
2.51
Adult nutritional powder milk-based
4
0.298
97.4
3.86
Adult nutritional RTF high protein
6
1.12
98.6
6.76
Child formula powder placebo
4
0.109
98.2
7.98
Adult nutritional RTF high fat
4
1.59
102
1.61
Infant elemental powder placebo
6
ND
b
105
4.45
Adult nutritional powder low fat
4
0.639
95.1
4.38
a
Results in µg/kg powder.
b
ND = Not detected.
Table 2011.10C. Interlaboratory study results for vitamin B
12
Sample type
Total No.
labs
Total No.
replicates
Mean
(µg/100 g RTF)
SD
r
SD
R
RSD
r
, % RSD
R
, % HorRat
a
Infant formula (NIST SRM 1849a)
10
20
43.7
b
3.01
3.86
6.90
8.84
0.34
Infant formula powder soy-based
10
20
0.428
0.0208 0.0305 4.85
7.13
0.20
Infant formula powder milk-based
9
18
0.227
0.0111 0.0202 4.90
8.90
0.22
Infant formula RTF milk-based
9
18
0.272
0.0257 0.0427 9.46
15.7
0.40
Infant formula powder partial
hydrolyzed milk-based
11
22
0.373
0.0200 0.0694 5.35
18.6
0.50
Infant formula powder partial
hydrolyzed soy-based
10
20
0.250
0.0244 0.0487 9.77
19.5
0.50
Adult nutritional powder milk-based
10
20
0.300
0.0270 0.0416 8.99
13.8
0.36
Adult nutritional RTF high protein
10
20
1.08
0.0730 0.190
6.74
17.5
0.55
Child formula powder
8
16
0.967
0.0289 0.0342 2.98
3.54
0.11
Adult nutritional RTF high fat
9
14
1.48
0.122 0.171
8.23
11.5
0.38
Infant elemental powder
9
18
0.543
0.0169 0.0603 3.11
11.1
0.32
Adult nutritional powder low fat
10
20
0.636
0.0348 0.0587 5.47
9.23
0.27
a
HorRat = RSD/PRSD
∙
PRSD = 2C
–0.15
(C = concentration by mass fraction).
b
Results in µg/kg powder.
Candidates for 2016 Method of the Year
340