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: J
ournal of
AOAC I
nternational
V
ol.
98, N
o.
6, 2015
1669
C. Chemicals and Solvents
(a)
Acetic acid.
—Glacial, ACS.
(b)
Chloroform.
—High-purity, HPLC grade.
(c)
Diethyl ether.
—Anhydrous, HPLC grade.
(d)
Drierite (desiccant).
—Anhydrous calcium sulfate,
8 mesh.
(e)
Helium.
—Zero grade or equivalent.
(f )
Hexane.
—HPLC grade.
(g)
Hydrochloric acid.
—Concentrated (36–38%), ACS.
(h)
Laboratory water.
—≥15 MΩ·cm.
(i)
Metaphosphoric acid.
—ACS.
(j)
Methanol.
—HPLC grade.
(k)
Myo-inositol.
—USP (Rockville, MD) reference standard,
official lot; store desiccated.
See
standard label for purity.
(l)
Sodium chloride.
—ACS.
(m)
Sodium hydroxide.
—50% (w/w), low carbonate form.
D. Preparation of Reagents and Standard Solutions
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)
Myo-inositol stock standard solution (approximately
2000 mg/L).
—Accurately weigh approximately 0.100 g
myo-inositol and quantitatively transfer to a 50 mL volumetric
flask. Dilute to volume with water. Mix well. Store refrigerated.
Expiration: 3 months.
(b)
Myo-inositol
intermediate
standard
solution
(approximately 200 mg/L).—
Dilute 10.0 mL stock standard to
100 mL with laboratory water and mix well. Discard after use.
(c)
Myo-inositol working standard solutions (approximately
4, 2, 1, 0.5, 0.2, and 0.05 mg/L).
—Dilute 2.0, 1.0, and 0.5 mL
myo-inositol intermediate standard to 100 mL with laboratory
water (4, 2, and 1mg/L). Dilute 0.5mLmyo-inositol intermediate
standard to 200 mL with laboratory water (0.5 mg/L). Dilute
4 and 1 mL 0.5 mg/L myo-inositol working standard to 10 mL
with laboratory water (0.2 and 0.05 mg/L). Expiration: 2 weeks.
(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 M.
—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 50% sodium hydroxide into a 2000 mL
volumetric flask containing approximately 1900 mL water.
Table 2011.18A. SLV repeatability precision data for myo-inositol
Sample type
No. of replicates
(duplicates on
multiple days)
Mean, mg/100 g RTF
SD
r
RSD
r
, %
Free myo-inositol
Infant formula (NIST SRM 1849a)
14
415
a
8.03
2.00
Infant formula powder soy-based
14
4.19
0.0910
2.17
Infant formula powder milk-based
14
4.21
0.0977
2.32
Infant formula RTF milk-based
14
7.19
0.250
3.48
Infant formula powder partial hydrolyzed milk-based
14
3.38
0.0997
2.95
Infant formula powder partial hydrolyzed soy-based
14
3.10
0.0626
2.02
Infant elemental powder
14
4.85
0.148
3.06
Child formula powder
14
5.04
0.112
2.22
Infant formula RTF milk-based, unfortified
14
3.17
0.0466
1.47
Infant elemental powder, unfortified
12
1.74
0.0329
1.89
Child formula powder, spiked
12
1.94
0.0477
2.46
Adult nutritional RTF high protein, spiked
12
61.4
1.87
3.05
Myo-inositol bound as phosphatidylinositol
Infant formula (NIST SRM 1849a)
12
10.6
a
0.536
5.05
Infant formula powder soy-based
12
2.48
0.0595
2.40
Infant formula powder partial hydrolyzed milk-based
12
0.244
0.00976
4.00
Infant formula powder partial hydrolyzed soy-based
12
1.98
0.0664
3.36
Child formula powder
12
0.443
0.0196
4.43
Adult nutritional powder, milk protein-based
12
1.43
0.067
4.69
Free myo-inositol plus myo-inositol bound as phosphatidylinositol
Infant formula (NIST SRM 1849a)
12
426
a
8.35
1.96
Infant formula powder soy-based
12
6.67
0.109
1.63
Infant formula powder partial hydrolyzed milk-based
12
3.63
0.100
2.76
Infant formula powder partial hydrolyzed soy-based
12
5.08
0.0914
1.80
Child formula powder
12
5.48
0.113
2.07
a
Results in mg/kg powder.
147