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: J
ournal of
AOAC I
nternational
V
ol.
98, N
o.
6, 2015
1671
1 mL 1 M NaCl and mix well. Centrifuge until layers separate.
Using a 25 mL glass tight syringe with a 4 in. stainless steel
needle, transfer the bottom chloroform layer to a clean 50 mL
centrifuge tube and evaporate the chloroform with nitrogen in
a 60°C water bath.
(
2
)
Sample cleanup
.—In a fume hood, condition a 1 g silica
SPE cartridge with 6 mL hexane. Dissolve residue in bottom
of centrifuge tube in 1 mL chloroform–methanol (2 + 1).
Quantitatively transfer dissolved residue to the conditioned
silica SPE cartridge. Rinse 50 mL centrifuge tube with 3 mL
hexane–diethyl ether (80 + 20) and then transfer to the SPE
cartridge. Discard the eluent. Rinse 50 mL centrifuge tube
with 3 mL hexane–diethyl ether (50 + 50) and then transfer to
the SPE cartridge. Collect eluent in a clean 50 mL centrifuge
tube. Rinse 50 mL centrifuge tube with 4 mL methanol and
then transfer to the SPE cartridge. Collect eluent in the same
Table 2011.18C. Interlaboratory study results for myo-inositol with all MLT data included and outliers removed
Sample type
Total No.
labs
Total No.
replicates
Mean,
mg/100 g
RTF
SD
r
SD
R
RSD
r
, % RSD
R
, % HorRat
a
Free myo-inositol
Infant formula (NIST SRM 1849a)
10
22
4.12
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
10
20
4.26
0.168
0.232
3.95
5.43
0.60
Infant formula RTF milk-based
9
20
7.17
0.095
0.207
1.33
2.89
0.34
Infant formula powder partial hydrolyzed milk-based 10
22
3.65
0.035
0.412
0.97
11.4
1.22
Infant formula powder partial hydrolyzed soy-based 10
22
3.11
0.0899
0.389
2.92
12.6
1.32
Child formula powder
10
22
5.10
0.185
0.246
3.61
4.81
0.54
Infant elemental powder
10
22
5.10
0.227
0.318
4.45
6.24
0.71
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)
9
20
9.51
b
1.82
2.62
18.7
26.8
2.36
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
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
9
18
4.92
0.184
0.314
3.74
6.38
0.72
Infant formula RTF milk-based
8
18
7.50
0.106
0.218
1.41
2.90
0.35
Infant formula powder partial hydrolyzed milk-based 9
20
3.84
0.035
0.426
0.91
11.2
1.21
Infant formula powder partial hydrolyzed soy-based
9
20
4.71
0.152
0.357
3.22
7.55
0.84
Child formula powder
9
20
5.42
0.203
0.307
3.73
5.63
0.64
Infant elemental powder
9
20
5.08
0.237
0.324
4.67
6.40
0.72
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.
Table 2011.18D. Instrument operating conditions
Pump 1 pressure limit
2000 psi
Pump 1 mobile phase
0.12% (30 mM) NaOH
Pump 1 flow rate
0.4 mL/min
Pump 2 pressure limit
2000 psi
Pump 2 mobile phase
4% (1 M) NaOH
Pump 2 flow rate
0.4 mL/min
Injection volume
20 µL
Myo-inositol retention time
11–13 min
Run time
25 min
Switching valve configuration time table
t, min
Configuration
0.00
1 (
see
Figure
2011.18A
)
1.50
2 (
see
Figure
2011.18B
)
13.50
1 (
see
Figure
2011.18A
)
149