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© 2015 AOAC INTERNATIONAL
AOAC Official Method 2011.18
Myo-Inositol
(Free and Bound as Phosphatidylinositol)
in Infant and Pediatric Formula
and Adult Nutritionals
Liquid Chromatography/Pulsed Amperometry
with Column Switching
First Action 2011
Final Action 2014
The liquid chromatography method with electrochemical (pulsed
amperometry) detection (PAD) allows for the quantitation of myo-
inositol in infant, pediatric, and adult nutritional formulas. The
concentration of myo-inositol is calculated by comparison with
standards of known concentration. Myo-inositol, as defined by
AOAC SMPR 2011.007 (free and bound as phosphatidylinositol),
can be calculated by adding the free myo-inositol and myo-inositol
bound as phosphatidylinositol data.
The method was validated for the quantitation of free myo-
inositol and myo-inositol from phosphatidylinositol in infant,
pediatric, and adult nutritionals. Repeatability was determined
from duplicate analyses performed on multiple days. Accuracy was
determined from spike recovery experiments (free myo-inositol
and myo-inositol from phosphatidylinositol). Instrument limits
of detection and quantitation were determined statistically from
injections of low-level standards and by spiking samples with low
levels of free myo-inositol.
See
Tables
2011.18A
–
C
for method performance information
supporting acceptance of the method.
Caution:
Refer toMaterial SafetyData Sheets (MSDS) of chemicals
prior to use and follow safe handling procedures and the
suggested personal protective equipment. Chloroform is
a hazardous chemical and should be handled in a fume
hood. Perform the phosphatidylinositol bound myo-
inositol extraction and SPE sample cleanup procedure in
a fume hood.
A. Apparatus
(
a
)
Analytical balance
.—Minimum weighing capacity of at
least 0.0001 g.
(
b
)
Centrifuge
.
(
c
)
Desiccator
.
Table 2011.18A. Single-laboratory validation: Repeatability precision data for myo-inositol
Sample type
No. of replicates
(duplicates on multiple days)
Mean
(mg/100 g RTF)
SD
r
RSD
r
Unbound (free) myo-inositol
Infant formula (NIST SRM 1849a)
14
415
a
8.30
2.00
Infant formula powder soy-based
14
4.19
0.091
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
Unbound (free) myo-inositol plus myo-inositol bound as phosphatidylinositol
Infant formula (NIST SRM 1849a)
12
426a
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.
Candidates for 2016 Method of the Year
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