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1674
Butler-Thompson et al.
: J
ournal of
AOAC I
nternational
V
ol.
98, N
o.
6, 2015
F. Calculations
Before calculating myo-inositol concentrations in samples,
compare the myo-inositol standard peaks with the myo-inositol
sample peaks and confirm that there are no interfering
compounds and that themyo-inositol sample peak areas or heights
are within the range of the myo-inositol standard peak areas or
heights. The concentration of myo-inositol cannot be calculated
if there are interferences or if the separation is poor. The
myo-inositol retention time should be 11 to 13 min depending on
the individual analytical column.
See
Figures
2011.18C
and
D
for typical standard and sample chromatograms, respectively.
(a)
Concentration of working standards:
C
W
= W × 1/0.05 × 1/10 × A
1
/V
1
× A
2
/V
2
× p =
W × 2 × A
1
/V
1
× A
2
/V
2
× p
where C
W
is the concentration of the working standard solution
in mg/L; W is the weight, in mg, of myo-inositol standard
weighed; 0.05 is the dilution volume of the stock standard
in L; 1/10 is the intermediate standard dilution (10 to 100 mL);
A
1
is the aliquot of intermediate standard used, in mL; V
1
is
the dilution volume of the working standard in mL; A
2
is the
aliquot of working standard used, in mL, if applicable; and
V
2
is the dilution volume of the working standard in mL, if
applicable; and p is the standard purity in mg/mg.
Table 2. Multilaboratory collaborative study data for phosphatidylinositol bound myo-inositol
a
Lab No. NIST 1849a
Infant partially
hydrolyzed milk
powder
Infant partially
hydrolyzed soy
powder
Child powder
Infant elemental
powder
Infant milk
powder
Infant soy
powder
Infant milk RTF
Infant milk RTF,
unfortified
1
13.4 13.7 0.296 0.296 2.25 2.11 0.513 0.500 0
0 0.954 0.960 2.93 2.83 0.519 0.522 0.469 0.451
2
11.3 10.0 0.221 0.232 1.91 1.78 0.411 0.405 0
0 0.809 0.724 2.41 2.24 0.361 0.324 0.262 0.278
3
6.25 9.34 0.201 0.188 1.53 1.56 0.322 0.301 0
0 0.583 0.579 2.07 2.20 0.333 0.289 0.290 0.218
4
6.77 8.22 0.160 0.167 1.42 1.36 0.250 0.316 0
0 0.402 0.387 1.34 1.72 0.272 0.341 0.265 0.328
5
8.21
b
15.3
b
0.243 0.221 1.93 1.75 0.353 0.351 0
0 0.697 0.754 2.06 2.47 NA
c
NA NA NA
6
NT
d
NT NT NT NT NT NT NT NT NT NT NT NT NT NT NT NT NT
7
10.9 10.9 0.307 0.312 1.41 1.46 0.367 0.340 0
0 0.681 0.654 1.91 1.90 0.448 0.363 0.382 0.352
8
7.50 8.89 0.175 0.166 1.25 1.24 0.198 0.204 0
0 0.454 0.450 1.63 1.56 0.213 0.251 0.199 0.211
6.15 6.33 0.173 0.189 1.11 1.13 0.233 0.254 0
0 NT NT 1.40 1.34 0.251 0.260 0.212 0.231
9
7.97 8.48 0.126 0.144 1.85 1.70 0.320 0.274 0
0 0.706 0.682 2.37 2.51 0.360 0.356 0.293 0.295
10
10.2 10.4 0.219 0.243 2.16 1.93 0.331 0.322 0
0 0.757 0.768 2.51 2.53 0.405 0.389 0.381 0.370
a
Concentration in mg/100 g RTF liquid for all products except NIST 1849a. NIST 1849a concentration in mg/kg powder.
b
Data excluded. Failed Cochran’s test.
c
NA = Not applicable. Laboratory did not receive sample.
d
NT = Not tested. Laboratory did not complete testing.
Table 3. Multilaboratory collaborative study data for free plus phosphatidylinositol bound myo-inositol
a
Lab No. NIST 1849a
Infant partially
hydrolyzed milk
powder
Infant partially
hydrolyzed soy
powder
Child powder
Infant elemental
powder
Infant milk
powder
Infant soy
powder
Infant milk RTF
Infant milk RTF,
unfortified
1
429 429 4.06 4.13 5.57 5.36 5.65 5.61 5.21 5.28 5.21 5.26 7.27 7.13 7.65 7.68 3.70 3.64
2
419 427 2.98
b
2.99
b
4.55 4.24 6.03 6.07 5.16 4.99 5.55 5.48 6.46 6.34 7.43 7.44 3.52 3.44
3
411 431 3.80 3.91 4.53 4.37 5.28 5.27 5.16 4.95 4.81 4.79 5.72 6.23 7.42 7.37 3.35 3.27
4
410 429 3.94 3.95 4.65 4.59 5.33 5.42 5.34 5.3 4.81 4.64 5.83 5.99 7.73 7.87 3.36 3.49
5
422 423 4.07 4.07 5.17 4.92 5.5 5.48 4.31
c
5.33
c
4.88 4.92 6.47 6.78 NA
d
NA NA NA
6
NT
e
NT NT NT NT NT NT NT NT NT NT NT NT NT NT NT NT NT
7
417 421 4.21 4.25 4.88 4.95 5.37 5.36 5.53 5.29 4.74 4.77 6.35 6.33 7.85 7.70 3.55 3.55
8
420 429 4.10 4.03 4.52 4.60 5.16 5.13 5.23 5.12 4.7 4.55 5.85 5.89 7.47 7.43 3.36 3.42
436 442 4.08 4.11 4.59 4.58 5.15 5.16 5.23 5.29 NT NT 5.81 5.77 7.47 7.36 3.41 3.45
9
386 428 3.93 3.95 4.70 4.49 5.85
c
4.91
c
4.96 4.85 5.12
c
4.39
c
6.54 6.33 7.47
c
7.06
c
3.24 3.43
10
414 413.0 3.18
b
3.15
b
4.70 4.24 5.30 5.35 4.58 4.44 5.00 4.87 6.17 6.19 7.27 7.29 3.52 3.61
a
Concentration in mg/100 g RTF liquid for all products except NIST 1849a. NIST 1849a concentration in mg/kg powder.
b
Data excluded. Failed Double Grubbs’ test.
c
Data excluded. Failed Cochran's test.
d
NA = Not applicable. Laboratory did not receive sample.
e
NT = Not tested. Laboratory did not complete testing.
152