6. AOACSPIFANMethods-2018Awards

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1674 Butler-Thompson et al. : J ournal of AOAC I nternational V ol. 98, N o. 6, 2015

Table 2. Multilaboratory collaborative study data for phosphatidylinositol bound myo-inositol a

Infant partially hydrolyzed milk powder

Infant partially hydrolyzed soy powder

Infant elemental powder

Infant milk powder

Infant soy powder

Infant milk RTF, unfortified

Lab No. NIST 1849a

Child powder

Infant milk RTF

1 2 3 4 5 6

13.4 13.7 0.296 0.296 2.25 2.11 0.513 0.500 0 11.3 10.0 0.221 0.232 1.91 1.78 0.411 0.405 0 6.25 9.34 0.201 0.188 1.53 1.56 0.322 0.301 0 6.77 8.22 0.160 0.167 1.42 1.36 0.250 0.316 0 8.21 b 15.3 b 0.243 0.221 1.93 1.75 0.353 0.351 0

0 0.954 0.960 2.93 2.83 0.519 0.522 0.469 0.451 0 0.809 0.724 2.41 2.24 0.361 0.324 0.262 0.278 0 0.583 0.579 2.07 2.20 0.333 0.289 0.290 0.218 0 0.402 0.387 1.34 1.72 0.272 0.341 0.265 0.328

0 0.697 0.754 2.06 2.47 NA c

NA NA NA

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.

C W

= W × 1/0.05 × 1/10 × A 1

/V 1

× A 2 × p

/V 2

× p =

F. Calculations

/V 1

× A 2

/V 2

W × 2 × A 1

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:

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 3. Multilaboratory collaborative study data for free plus phosphatidylinositol bound myo-inositol a

Infant partially hydrolyzed milk powder

Infant partially hydrolyzed soy powder

Infant elemental powder

Infant milk powder

Infant soy powder

Infant milk RTF, unfortified

Lab No. NIST 1849a

Child powder

Infant milk RTF

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.