
Contents
33.2.07
AOAC Official Method 932.05
Citric Acid in Milk: Gravimetric Method
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Published:January 2023
Cite
Citric Acid in Milk: Gravimetric Method', in Dr. George W Latimer, Jr. (ed.), Official Methods of Analysis of AOAC INTERNATIONAL, 22nd Edition (
Extract
First Action 1932
Final Action
Preparation of Test Solution
To 50 g milk in 150 mL beaker, add ca 100 mg tartaric acid and 6 mL 0.5 M H2SO4, and heat on steam bath 15 min. Immediately add 3 mL 20% phosphotungstic acid solution (w/v), mix well, and return to steam bath for 5 min. Transfer to 250 mL volumetric flask with alcohol, cool, dilute to volume with alcohol, mix, and filter through folded paper. Pipet 200 mL clear filtrate into centrifuge bottle.
Reagents
...
Determination
To solution in centrifuge bottle add 10 mL Pb(CH3COO)2 solution, shake vigorously ca 2 min, and centrifuge 15 min at ca 1000 rpm. Carefully decant supernate from precipitated Pb salts and test with little Pb(CH3COO)2 solution. If precipitate forms, return to centrifuge bottle, add more Pb solution, shake, and again centrifuge. If sediment lifts, centrifuge again, increasing speed and time, and decant. Invert bottle and drain thoroughly several minutes. To Pb salts in centrifuge bottle add ca 150 mL H2O, shake thoroughly, and saturate with H2S. Transfer to 250 mL volume flask, dilute to volume with H2O, mix, and filter through folded paper.
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