6. AOACSPIFANMethods-2018Awards

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Butler-Thompson et al. : J ournal of AOAC I nternational V ol. 98, N o. 6, 2015  1671

Table 2011.18C. Interlaboratory study results for myo-inositol with all MLT data included and outliers removed

Mean, mg/100 g RTF

Total No. labs

Total No. replicates

, % HorRat a

Sample type

SD r

SD R

RSD r

, % RSD R

Free myo-inositol

4.12 b 4.22 4.26 7.17 3.65 3.11 5.10 5.10 3.17

11.3

11.4

2.75 3.03 3.95 1.33 0.97 2.92 3.61 4.45 1.84 18.7 6.94 3.92 8.36 4.72 5.53 6.89 0.00 7.71 2.83 2.32 3.74 1.41 0.91 3.22 3.73 4.67 1.90

2.77 7.26 5.43 2.89 11.4 12.6 4.81 6.24 2.87 26.8 23.2 25.9 25.2 26.4 21.1 25.8 0.00 26.9 2.83 7.05 6.38 2.90 11.2 7.55 5.63 6.40 3.70

0.43 0.80 0.60 0.34 1.22 1.32 0.54 0.71 0.30 2.36 2.30 2.15 1.91 1.86 2.02 1.94 0.00 2.00 0.44 0.82 0.72 0.35 1.21 0.84 0.64 0.72 0.39

Infant formula (NIST SRM 1849a) Infant formula powder soy-based Infant formula powder milk-based Infant formula RTF milk-based

10 10 10

22 22 20 20 22 22 22 22 20 20 20 18 18 20 20 20 20 18 20 20 18 18 20 20 20 20 18

0.127 0.168 0.095 0.035

0.305 0.232 0.207 0.412 0.389 0.246 0.318

9

Infant formula powder partial hydrolyzed milk-based 10 Infant formula powder partial hydrolyzed soy-based 10

0.0899

Child formula powder Infant elemental powder

10 10

0.185 0.227

Infant formula RTF milk-based, unfortified

9

0.0582

0.0910

Myo-inositol bound as phosphatidylinositol

9.51 b

1.82

2.62

Infant formula (NIST SRM 1849a) Infant formula powder soy-based Infant formula powder milk-based Infant formula RTF milk-based

9 9 9 8

2.10

0.150

0.501 0.172

0.667 0.348 0.214

0.0261 0.0301 0.0103 0.0936 0.0234

0.0909 0.0576

Infant formula powder partial hydrolyzed milk-based 9 Infant formula powder partial hydrolyzed soy-based 9

1.64

0.358

Child formula powder Infant elemental powder

9 9 8 9 9 9 8 9 9 9 8

0.328

0.0878

0.00

0.00

0.00

Infant formula RTF milk-based, unfortified

0.305

0.0244

0.0850

Free myo-inositol plus myo-inositol bound as phosphatidylinositol

422 b 6.27 4.92 7.50 3.84 4.71 5.42 5.08 3.46

11.9

11.9

Infant formula (NIST SRM 1849a) Infant formula powder soy-based Infant formula powder milk-based Infant formula RTF milk-based

0.147 0.184 0.106 0.035 0.152 0.203 0.237

0.446 0.314 0.218 0.426 0.357 0.307 0.324 0.128

Infant formula powder partial hydrolyzed milk-based 9

Infant formula powder partial hydrolyzed soy-based

Child formula powder Infant elemental powder

Infant formula RTF milk-based, unfortified

0.0659

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

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

0.12% (30 mM) NaOH

Pump 1 flow rate

0.4 mL/min

Pump 2 pressure limit Pump 2 mobile phase

2000 psi

4% (1 M) NaOH

Pump 2 flow rate Injection volume

0.4 mL/min

20 µL

Myo-inositol retention time

11–13 min

Run time

25 min

Switching valve configuration time table

t, min

Configuration

1 ( see Figure 2011.18A ) 2 ( see Figure 2011.18B ) 1 ( see Figure 2011.18A )

0.00 1.50

13.50