4.8.03 AOAC of Fi Cial Method 927.02 Cal Cium in An I Mal Feed

 

4.8.03 AOAC Offi Official Method 927.02 Calcium Cal cium in Ani Animal Feed Dry Ash Method First Action Action 1927 Final Fi nal Action Action 1945

(Ap pli  plica ca ble to mineral mineral feeds only.) Weigh 2 g finely ground test portion por tion into SiO2 or porce porcelain dish and ignite ignite in fur C-free butHNO avoid .fusing. fus ing. fer Boiltoresi res iduemL in 40 mL HCl (1 nace + 3) toand fewash, drops Trans 250 3 Transfer volu vol umet metric ric flask, cool, dilute dilute to volume, volume, and mix thoroughly. thor oughly. Pipet 25 mL clear liquid liquid into beaker, dilute di lute to ca 100 mL, and add 2 drops methyl red, 984.13B 984.13B((c) ( see 4.2.09). Add NH 4OH (1 + 1) dropwise to pH 5.6, as shown by inter in ter medi me diate ate brownish-orange. If  overstepped, over stepped, add HCl (1 + 3) with drop per drop per to or ange. Add 2 more drops HCl (1 + 3). Color should now be pink (pH 2.5–3.0), not orange. or ange. Di lute to ca 150 mL, bring to boil, bo il, and slowly add, with constant con stant stirring, stir ring, 10 mL hot satu sat u rated (4.2%) solu so lution tion of  (NH4)2C2O4. If red changes to orange orange or yellow, yellow, add HCl (1 + 3) dropwise until until color again changes to pink. Let stand overnight over night for   precip  pre cipiitate to settle. settle. Filter Filter supernate through quanti quantita tative tive pa per, Gooch, or fritted glass filter fil ter (fine Pyrex Pyrex is prefer preferaa ble), and wash  precip  pre cipiitate thoroughly thoroughly with NH4OH (1 + 50). Place pa per pa per or cru cruci ci ble  ble with pre cipitate in origi original beaker, and add mixture mixture of 125 mL H2O and 5 mL H2SO4. Heat to 70C and titrate with 0.02M KMnO 4, 940.35  ( see A.1.10), to first slight pink. Presence 940.35 Presence of pa per may cause color to fade in few s. Cor Co rrect for blank and calcu calculate late percent percent Ca. 1 mL 0.02M KMnO4 = 2.004 mg Ca Refer Ref erences: ences:  JAOAC  10, 177(1927); 19, 93, 574(1936); 28, 80(1945). CAS-7440-70-2 (calcium) (calcium)

 2008 AOAC IN TER TERNA NATIONAL TIONAL