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© 2015 AOAC INTERNATIONAL
(
d
)
Hydrochloric acid, 0.5%.—
Add 1.25 mL concentrated
hydrochloric acid to approximately 200 mL water in a 250 mL
volumetric flask. Dilute to volume with water and mix well.
Expiration: 6 months.
(
e
)
Sodium chloride, 1 N.—
Dissolve 5.8 g sodium chloride and
dilute to 100 mL with water. Expiration: 1 month.
(
f
)
Sodium hydroxide, 0.12% or 30 mM (Pump 1).—
Quickly
weigh 4.8 (±0.1) g of 50% sodium hydroxide into a 2000 mL
volumetric flask containing approximately 1900 mL water. (
Note
:
It is important that the sodium hydroxide does not absorb carbon
dioxide from the air.) Swirl to mix well. Dilute to volume with
water and mix well. Expiration: 1 month.
(
g
)
Sodium hydroxide, 4.0% or 1 M (Pump 2).—
Quickly weigh
160 (±3) g of 50% sodium hydroxide into a 2000 mL volumetric
flask containing approximately 1900mLwater. (
Note
: It is important
that the sodium hydroxide does not absorb carbon dioxide from the
air.) Swirl to mix well. Dilute to volume with water and mix well.
Expiration: 1 month.
(
h
)
6% Metaphosphoric acid.—
Weigh 6.0 g metaphosphoric
acid into a 100 mL volumetric flask. Dissolve and dilute to volume
with laboratory water. Mix well. Store refrigerated. Expiration:
1 week.
(
i
)
Phosphatidylinositol extraction solutions.—
Prepare fresh on
day of use.
(
1
)
Chloroform–methanol (2:1)
.—Mix 60 mL chloroform and
30 mL methanol.
(
2
)
Hexane–diethyl ether (80:20)
.—Mix 80 mL hexane and
20 mL diethyl ether.
Table 2011.18C. Interlaboratory study results for myo-inositol
Sample type
Total No.
labs
Total No.
replicates
Mean
(mg/100 g RTF) SD
r
SD
R
RSD
r
RSD
R
HorRat
a
Unbound (free) myo-inositol
Infant formula (NIST SRM 1849a)
10
22
412
b
11.3 11.4 2.75 2.77 0.43
Infant formula powder soy-based
10
22
4.22
0.127 0.305 3.03 7.26 0.80
Infant formula powder milk-based
8
16
4.23
0.0660 0.109 1.56 2.57 0.28
Infant formula RTF milk-based
8
18
7.20
0.0455 0.185 0.63 2.57 0.31
Infant formula powder partial hydrolyzed milk-based
8
18
3.83
0.0368 0.0892 0.96 2.33 0.25
Infant formula powder partial hydrolyzed soy-based
10
22
3.11
0.0899 0.389 2.92 12.61 1.32
Child formula powder
8
18
5.05
0.0233 0.109 0.46 2.15 0.24
Infant elemental powder
9
20
5.13
0.0950 0.277 1.85 5.41 0.61
Infant formula RTF milk-based, unfortified
9
20
3.17
0.0582 0.0910 1.84 2.87 0.30
Myo-inositol bound as phosphatidylinositol
Infant formula (NIST SRM 1849a)
8
18
9.26
b
1.08 2.37 11.3 25.0 2.19
Infant formula powder soy-based
9
20
2.10
0.150 0.501 6.94 23.2 2.30
Infant formula powder milk-based
9
18
0.667
0.0261 0.172 3.92 25.9 2.15
Infant formula RTF milk-based
8
18
0.348
0.0301 0.0909 8.36 25.2 1.91
Infant formula powder partial hydrolyzed milk-based
9
20
0.214
0.0103 0.0576 4.72 26.4 1.86
Infant formula powder partial hydrolyzed soy-based
9
20
1.64
0.0936 0.358 5.53 21.1 2.02
Child formula powder
9
20
0.328
0.0234 0.0878 6.89 25.8 1.94
Infant elemental powder
9
20
0.00
0.00 0.00 0.00 0.00 0.00
Infant formula RTF milk-based, unfortified
8
18
0.305
0.0244 0.0850 7.71 26.9 2.00
Unbound (free) myo-inositol plus myo-inositol bound as phosphatidylinositol
Infant formula (NIST SRM 1849a)
9
20
422
b
11.9 11.9 2.83 2.83 0.44
Infant formula powder soy-based
9
20
6.27
0.147 0.446 2.32 7.05 0.82
Infant formula powder milk-based
8
16
4.94
0.0696 0.302 1.41 6.12 0.69
Infant formula RTF milk-based
7
16
7.53
0.0588 0.201 0.78 2.66 0.32
Infant formula powder partial hydrolyzed milk-based
7
16
4.04
0.0380 0.124 0.94 3.07 0.33
Infant formula powder partial hydrolyzed soy-based
9
20
4.71
0.152 0.357 3.22 7.55 0.84
Child formula powder
8
18
5.42
0.0280 0.285 0.51 5.23 0.60
Infant elemental powder
8
18
5.11
0.0990 0.283 1.94 5.56 0.63
Infant formula RTF milk-based, unfortified
8
18
3.46
0.0659 0.128 1.90 3.70 0.39
a
HorRat = RSD/PRSD
∙
PRSD = 2C
–0.15
(C = concentration by mass fraction).
b
Results in mg/kg powder.
Candidates for 2016 Method of the Year
347