OMB Meeting Book - Jan. 11, 2018

( e )  Combined ring silver electrode.— e.g., Mettler Toledo DM 141 or DMi145-SC, or equivalent; alternatively, a silver electrode with reference electrode can be used. ( f )  Magnetic stirrer.— Heidolph MR 3000 or equivalent (Sigma- Aldrich, St. Louis, MO, USA). ( g )  Water bath .—Capable of warming water to 40°C. ( h )  Laboratory oven.— Capable of heating to 120°C. ( i )  Pipets (1, 20, 50, and 100 mL) .—Class A glass volumetric or automatic (Eppendorf or equivalent). ( j )  Buret.— 10 mL. C. Chemicals and Reagents ( a )  Acetone.— p.a. (Merck, Darmstadt, Germany, or equivalent). ( b )  Water, purified.— Greater than 18MΩ (EMD Millipore Corp., Billerica, MA, USA, or equivalent). ( c )  Sodium chloride (NaCl) , crystal .—Fluka 71387 (Sigma-Aldrich, or equivalent). ( d )  AgNO 3 .—Sigma-Aldrich 10220, or equivalent. D. Solutions ( a )  Nitric acid.— Minimum 65% p.a. (Merck, or equivalent). ( b )  Standardized AgNO 3 solution, 0.1 M.— Merck TitriPUR, or equivalent. ( c )  NaCl solution, 0.1 M .—Alfa Aesar (Ward Hill, MA, USA), or equivalent. E. Preparation of Solutions ( a )  Dilute nitric acid solution, 2% (v/v).— Into a 1000 mL volumetric flask, add about 800 mL water. Carefully pipet 20 mL concentrated nitric acid (65%). Make up to 1000 mL with water. Stopper the volumetric flask and mix well.

AOAC Official Method 2015.08 Chloride in Infant Formula and Adult/Pediatric Nutritional Formula Potentiometry First Action 2015

[Applicable to the determination of chloride in ready-to-feed (RTF) liquid concentrate and powder products from levels of 1.4 to 1060 mg/100 g reconstituted product or RTF liquids.] See Tables 2015.08 A – C for the results of the single-laboratory validation (SLV) study supporting acceptance of the method. The method was evaluated against Standard Method Performance Requirements AOAC SMPR ® 2014.015. A. Principle Reconstitute powder samples by dissolving 25 g powder sample in 200 g warm water (40°C). Add 50 mL of 2% (v/v) nitric acid solution. Stir with a magnetic stirrer until mixed or finely suspended. Ensure pH is <1.5. Titrate potentiometrically against standardized silver nitrate (AgNO 3 ) solution, 0.1 M, using a silver electrode to detect the end point. B. Apparatus Common laboratory equipment and, in particular, the following: ( a )  Analytical balance.— Precision 0.1 mg. ( b )  Class A volumetric flasks.— 100 and 1000 mL. ( c )  pH meter/mV meter with a scale covering ±700 mV, and buret, 20 or 25 mL.— Mettler-Toledo (Columbus, OH, USA) or equivalent. ( d )  Automatic titrator. —Autosampler, motorized piston buret, with remote-control dispensing and filling (Mettler Toledo T50 Rondo Tower autosampler, Mettler LabX 3.1 software, or equivalent).

Table 2015.08A. Precision of results expressed on reconstituted product Matrix a

Chloride mean, mg/100 g

RSD r

, % b

RSD

, % c

R

NIST SRM 1849a

68.5 46.1 36.8 38.2 30.8 20.0 36.4 42.4 46.2 40.3 38.6 39.3 46.5 56.1 44.2

0.42 0.26 0.10 0.64 2.77 0.22 0.45 0.09 0.15 0.20 0.67 0.21 0.88 0.29 0.34 0.44 1.01

1.59 0.32 0.12 2.76 0.18 0.47 0.13 0.16 0.18 0.81 0.23 0.85 0.33 0.24 0.40

Child formula powder Infant elemental powder

Adult nutritional RTF, high protein Adult nutritional RTF, high fat

10.09 d

Infant formula RTF, milk based (SPIFAN blank milk formula)

Adult nutritional powder milk, protein based

Infant formula powder partially hydrolyzed, milk based Infant formula powder partially hydrolyzed, soy based

Adult nutritional powder low fat

Child formula powder Infant elemental powder

Infant formula powder, milk based Infant formula powder, soy based

Infant formula RTF, milk based (SPIFAN control milk formula)

Adult nutritional RTF, high protein Adult nutritional RTF, high fat

154.5 162.2

0.78 a  Samples provided in the SPIFAN I Test Kit. SRM 1849a was reconstituted 10 g to 100 g, and all other powders were reconstituted 25 g to 225 g. b  RSD r = Repeatability RSD. c  RSD R = Reproducibility RSD. d  Higher repeatability and intermediate reproducibility were observed in this nonfortified RTF sample compared to the rest of the samples. This is most likely due to sample heterogeneity, since the sample was beyond its expiration date. The sample contents separated even after 15 min shaking prior to opening. These results were not included in the evaluation. Additional high-fat sample was within the SMPR requirements.

© 2015 AOAC INTERNATIONAL

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