animal feed minerals procedures

7/27/2019 Animal Feed Minerals Procedures

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AOAC Official Method 927.02

Calcium in Animal Feed

Dry Ash Method Final Action

(Application to mineral feeds only)

Weigh 2 g finely ground sample into SiO2 or porcelain dish and ignite in furnace to C-free ash, but avoid fusing. Boil residue in 40 mL HCL (1 + 3) and few drops HNO3. Transfer to 250 mL

volumetric flask, cool, dilute to volume, and mix thoroughly. Pipet 25 mL clear liquid into

beaker, dilute to ca 100 mL, and add 2 drops methyl red, 984.13B(c) (see 4.2.09) Add NH4OH

(1 + 1) dropwise to pH 5.6, as shown by intermediate brownish-orange. If overstepped, add HCL(1 +3) with dropper to orange. Add 2 more drops HCL (1 + 3). Color should now be pink

(pH2.5-3.0),not orange. Dilute to ca 150 mL, bring to boil, and slowly add, with constantstirring, 10 mL hot saturated (4.2%) solution of (NH4)2C2O4. If red changes to orange oryellow, add HCL (1 + 3) dropwise until color again changes to pink. Let stand overnight for

precipitate to settle. Filter supernate through quantitative paper, Gooch, or fritted glass filter (fine

Pyrex is preferable), and wash precipitate thoroughly with NH4OH (1 + 50). Place paper orcrucible with precipitate in original beaker, and add mixture of 125 mL H2O and 5 mL H2SO4.

Heat to 70 and titrate with 0.1 N KMnO4. 940.35 (see A.1.10), to first slight pink. Presence of

paper may cause color to fade in few s. Correct for blank and calculate % Ca.

References: JAOAC 10, 177(1927); 19,93,574(1936); 28,80(1945).

CAS-7440-70-2 (calcium)

AOAC Official Method 935.13

Calcium in Animal Feed

Wet Ash Method - Final Action

A. Preparation of Solution

(Caution: See Appendix B, safety notes on nitric acid and perchloric acid.)



(a) Weigh 2.5 g sample into 500 or 800 mL Kjeldahl flask. Add 20-30 mL HNO3 and boil gently

30-45 min to oxidize all easily oxidizable matter. Cool solution somewhat and add 10 mL 70-72% HCIO4. Boil very gently, adjusting flame as necessary, until solution is colorless or nearly

so and dense whit fumes appear. Use particular care not to boil to dryness (Danger!) At any time.

Cool slightly, add 50 mL H2O, and boil to drive out any remaining NO2 fumes. Cool, diluted,

filter into 250 mL volumetric flask, dilute to volume, and mix thoroughly.

(b) Weigh 2.5 g finely ground sample into SiO2 or porcelain dish and ignite as in 942.05 (see

4.1.10). Add 40 mL HCL (1 + 3) and few drops HNO3 to residue, boil, transfer to 250 mL

volumetric flask, cool, dilute to volume, and mix thoroughly.

B. Determination

Pipet suitable aliquot of clear solution, 935.13A(a) or(b),into beaker, dilute to 100 mL, and add 2

drops methyl red, 984.13B(c) (see 4.2.09). Continue as in 927.02 (see 4.8.03), beginning "Add

NH4OH (1 + 1) dropwise . . ." except use 0.05N KMnO4 for titration.

(100 mL is suitable aliquot of sample solution for grain feeds; for mineral feeds, 25 mL aliquot

may be taken and titrated with 0.1N KMnO4. For suitable precision, size of sample, aliquot, and

concentration of KMnO4 must be so adjusted that 20 mL standard KMnO4 solution is used.)

References: Ind. Eng. Chem. Anal. Ed. 7, 116, 167(1935).

JAOAC 30, 606(1947); 31, 98(1948); 32, 650(1949); 33, 162(1950); 34,563(1951).

CAS-7440-70-2 (calcium)

AOAC OFFICIAL METHOD 964.06

Phosphorus in Animal Feed

Alkalimeric Ammomonium

Molybdophosphate Method

Final Action



A Regents

(a) Mollybdatesolution.-Disslove 100 g MoO3 in mixture of 144 mL NH4Oh and 271 mL water.Coll, and slowly pour solution, stirring constantly. Into cool mixture of 489mL HNO3 and

1148mL water. Kee final mixture in warm place several days or until portion heated to 40"

deposits no yellow precipitate. Decant solution from any sediment and keep in glass-stoppervessels.

(b) Acidfied molydate solution.- to 100 mL molybdate solution, (a), add 5mL HNO3. Filter

immediately before use.

(c) Sodium hydroxide standard solution.- Dilute 324.03mL 1N alkali, carbonate-free, 936.16(see

A. 1.12) to 1L. (100 mL of this solution shold neutralize32.40 mL 1N acid: 1mL=1mg or 1%

P2o% on basis of 0.1 g sampl.) ( Since burets in constant use may become so corroded as to

increase their capasity, teast them at least annually.)

(D) Standard acid solution- Prepare solution of Hcl or of HNO3, corespond to concetration of (c)or to ½ this concentratiion, and tandardize bytitration against (c) using phenolphthalein.

B. Determination

Prepare samloe soltion as in 935.13A (a)( see 4.8.04). Pipet, into beaker or flask, aliquot

correspondingto 0.4 g sample for P2ocontent of sample < 5%;0.2 for 5-20%. 0.1 g for .20%. Add

5-10 mL HNO3. Depending on method of solution ( or equivalent in NH4NO3 ): then add NH4OH until precipitate that forms dissolves Only slowly on vigorous stirring. Dilute to 75-100

mL, and adjust to 25-30". If sample does not give precipitate with NH4OH as test of

neutralization, make solution slightly aldaline to litmus paper with NH4OH and slightly acidwithHNO3 (1+3). Add 20-25 mL for 5-20%; and enough acidified molybate solution to ensure

complete precipitation for >20%. Shade or stir mechanically 30 min at room temperature: decant

at once through filter and wash precipitate twice by decanting with 25-30 mL portions water,agitating thorough and allowing to settle. Transfer precipitate to filter and wash with cold water

until filtrate from 2fillgs of filter yeilds pink color on adding phenolphthalein and 1 drop of thestandard alkali transfer precipitate and filter to beaker or precipitating vessel, dissolve precipitate

in small excess of the standard alkali, add few drops of phenolphalein, and titrate with standard

acid. Report as % P.

animal feed minerals procedures

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