AOAC-968.35-(16.4.04).pdf
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1、16.4.04 AOAC Of fi cial Method 968.35 Filth and Ex tra ne ous Ma te rial in Pea nut But ter Sedimentation/Flotation Methods First Ac tion 1968 Fi nal Ac tion 1988 A. Prep a ra tion of Sam ple Examine individually at least 3, and preferably 6, jars. If jars contain 1 lb each, make 36 composites of 2
2、jars each so that composite sample will be ca 1 lb. Remove contents of each jar and mix thoroughly, preferably in evaporating dishes of convenient size, using heavy table fork or spatula. Peanut butter after warming may also be mixed in the jar by means of mixer, 945.75B(e) (see 16.1.01), equipped w
3、ith stiff paddles. If large number of jars is to be examined, make composite samples by thoroughly mixing contents of 36 jars of equal size. B. Wa ter-Insoluble In or ganic Res i due (“WIIR”) and Ex creta (Caution: See Appendix B, Distillation, Flammable Solvents, Toxic Solvents, Chloroform, Petrole
4、um Ether.) Weigh 100 g sample into 250 mL beaker (hooked-lip type), add ca 10 mL petroleum ether, and mix thoroughly. Continue to add petroleum ether, mixing thoroughly until ca 150 mL has been added. Cover, let settle 25 min, and decant 100 mL petroleum ether layer and floating light tissue without
5、 losing any coarse peanut tissue. Add ca 125 mL petroleum ether to residue and mix, let settle 15 min, and decant 100 mL as before. Repeat with third ca 125 mL addition petroleum ether, stir, wash down sides of beaker with stream of petroleum ether, let settle 10 min, and decant 100 mL. Discard all
6、decanted portions of petroleum ether. Evaporate remainder of petroleum ether from residue in beaker; gentle heat may be used. Add 150 mL CHCl3 to residue and mix thoroughly; cover beaker and let settle 20 min. Stir top layer several times during this period. Carefully decant CHCl3 and floating peanu
7、t tissue onto 15 cm paper in Bchner without disturbing heavy residue in bottom of beaker. Repeat extraction with small amounts of CHCl3, rinsing all particles from sides of beaker. At this point, watch for fragments of rodent excreta pellets on top of NaCl in bottom of beaker; do not decant them. (I
8、f sample contains considerable peanut skin, it may be necessary to use mixture of CHCl3 and just enough CCl4 to float skin particles away from heavy residue of NaCl, sand, etc.) Dry residue in air. Add 50 mL HCl (1 + 35) to residue in beaker; then add 90 mL boiling water and let stand 30 min with oc
9、casional stirring to dissolve any phosphate, carbonate, or anhydrite (CaSO4) included with the NaCl. Decant liquid through ashless filter in 60? glass funnel and finally transfer residue with hot water. Test filtrate for sulfate by adding 5 mL saturated BaCl2 solution. Wash residue on filter several
10、 times with hot water. If test for sulfate in filtrate was positive, test residue on filter by placing clean beaker or test tube under funnel and treating residue with 25 mL HCl (1 + 35), adding little at time. Test filtrate with 20 drops saturated BaCl2 solution (fine white ppt of BaSO4 indicates p
11、resence of anhydrite in residue on filter; allow 5 min for ppt to appear). Wash residue on filter with hot water until all HCl is removed. Examine residue microscopically for fragments of rodent excreta pellets (identified by presence of rodent hair fragments in mass), insect excreta pellets, and ot
12、her filth. Ignite paper in weighed crucible over medium Bunsen flame or in furnace at ca 500?C. Cool, and weigh crucible and contents to nearest 0.5 mg. If “WIIR” is excessive and application of above test indicates that all CaSO4 has not been removed, make quantitative determination of either Ca or
13、 sulfate in “WIIR” in crucible, as in 925.55(F) or (G) (see 11.2.01). Calculate this weight to CaSO4 and correct weight of “WIIR.” C. Rocks and De com posed Pea nuts (Caution: See Appendix B, Toxic Solvents, Carbon Tetrachloride.) Remove entire contents of jar to 1.5 L beaker or other suitable conta
14、iner. Add ca 700 mL CCl4 and mix thoroughly, using mixer, 945.75B(e) (see 16.1.01), if convenient. Rinse jar with CCl4 and add rinsings to beaker. Let mixture stand 15 min with occasional stirring. Decant ca 2/3 of mixture and add ca 200 mL CCl4. Let stand 5 min and decant. Wash down sides of beaker
15、 with CCl4 and repeat decantation until residue is free from peanut tissue. Save all decanted material. Dry residue in beaker and wash out salt with hot water. If large amount of sand is present, wash residue to remove, slat, phosphate, carbonate, and anhydrite as in B, 4th paragraph. Transfer resid
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