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Butler-Thompson et al. : J ournal of AOAC I nternational V ol. 98, N o. 6, 2015  1669

Table 2011.18A. SLV repeatability precision data for myo-inositol

No. of replicates (duplicates on multiple days)

Sample type

RSD r

, %

Mean, mg/100 g RTF

SD r

Free myo-inositol

415 a 4.19 4.21 7.19 3.38 3.10 4.85 5.04 3.17 1.74 1.94 61.4

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

14 14 14 14 14 14 14 14 14 12 12 12 12 12 12 12 12 12 12 12 12 12 12

8.03

2.00 2.17 2.32 3.48 2.95 2.02 3.06 2.22 1.47 1.89 2.46 3.05 5.05 2.40 4.00 3.36 4.43 4.69 1.96 1.63 2.76 1.80 2.07

0.0910 0.0977

0.250

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

0.0997 0.0626

Infant elemental powder Child formula powder

0.148 0.112

Infant formula RTF milk-based, unfortified Infant elemental powder, unfortified

0.0466 0.0329 0.0477

Child formula powder, spiked

Adult nutritional RTF high protein, spiked

1.87

Myo-inositol bound as phosphatidylinositol

10.6 a

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

0.536

2.48

0.0595 0.00976 0.0664 0.0196

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

0.244

1.98

Child formula powder

0.443

Adult nutritional powder, milk protein-based

1.43

0.067

Free myo-inositol plus myo-inositol bound as phosphatidylinositol

426 a 6.67 3.63 5.08 5.48

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

8.35

0.109 0.100

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

0.0914

Child formula powder

0.113

a  Results in mg/kg powder.

(a)  Myo-inositol stock standard solution (approximately 2000 mg/L). —Accurately weigh approximately 0.100 g myo-inositol and quantitatively transfer to a 50 mL volumetric flask. Dilute to volume with water. Mix well. Store refrigerated. Expiration: 3 months. (b)  Myo-inositol intermediate standard solution (approximately 200 mg/L).— Dilute 10.0 mL stock standard to 100 mL with laboratory water and mix well. Discard after use. (c)  Myo-inositol working standard solutions (approximately 4, 2, 1, 0.5, 0.2, and 0.05 mg/L). —Dilute 2.0, 1.0, and 0.5 mL myo-inositol intermediate standard to 100 mL with laboratory water (4, 2, and 1mg/L). Dilute 0.5mLmyo-inositol intermediate standard to 200 mL with laboratory water (0.5 mg/L). Dilute 4 and 1 mL 0.5 mg/L myo-inositol working standard to 10 mL with laboratory water (0.2 and 0.05 mg/L). Expiration: 2 weeks. (d)  Hydrochloric acid, 0.5%. —Add 1.25 mL concentrated hydrochloric acid to approximately 200 mL water in a 250 mL volumetric flask. Dilute to volume with water and mix well. Expiration: 6 months. (e)  Sodium chloride, 1 M. —Dissolve 5.8 g sodium chloride and dilute to 100 mL with water. Expiration: 1 month. (f )  Sodium hydroxide, 0.12% or 30 mM (Pump 1). —Quickly weigh 4.8 (±0.1) g 50% sodium hydroxide into a 2000 mL volumetric flask containing approximately 1900 mL water.

C. Chemicals and Solvents

(a)  Acetic acid. —Glacial, ACS. (b)  Chloroform. —High-purity, HPLC grade. (c)  Diethyl ether. —Anhydrous, HPLC grade. (d)  Drierite (desiccant). —Anhydrous calcium sulfate, 8 mesh. (e)  Helium. —Zero grade or equivalent. (f )  Hexane. —HPLC grade. (g)  Hydrochloric acid. —Concentrated (36–38%), ACS. (h)  Laboratory water. —≥15 MΩ·cm. (i)  Metaphosphoric acid. —ACS. (j)  Methanol. —HPLC grade. (k)  Myo-inositol. —USP (Rockville, MD) reference standard, official lot; store desiccated. See standard label for purity. (l)  Sodium chloride. —ACS. (m)  Sodium hydroxide. —50% (w/w), low carbonate form.

D. Preparation of Reagents and Standard Solutions

All solutions can be scaled up or down for convenience provided good laboratory practices are observed. Solutions can be stored at 2–30°C in tight, inert containers unless otherwise noted.