AOAC Official Method 999
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09E745BCF2EA45B49482A39C15F79215 |
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0.1 |
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3 |
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日期： |
2016-2-28 |
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9.1.09,AOAC Of fi cial Method 999.11,Lead, Cad mium, Cop per, Iron, and Zinc,in Foods,Atomic Absorption Spectrophotometry,after Dry Ashing,First Ac tion 1999,Final Action 2005,NMKL–AOAC Method,[Ap pli ca ble to de ter mi na tion of Zn, Cu, and Fe in a va ri ety of,foods by dry ashing and flame atomic ab sorp tion spec trom e try,(FAAS), and Cd and Pb by dry ashing and graph ite fur nace atomic,ab sorp tion spec trometry (GFAAS). Method is ca pa ble of,de ter min ing these el e ments at con cen tra tions above ap prox i mately,Pb, 0.3; Cd, 0.1; Zn, 1; Cu, 5; and Fe, 4 mg/kg.],See Ta ble 999.11A for the re sults of the interlaboratory study,sup port ing ac cep tance of the method.,Cau tion: Al ways gently add acid to wa ter. Avoid en vi ron men tal,con tam i na tion by Pb. Store quartz cru ci bles in 20%,HNO3 and rinse with deionized wa ter be fore use.,When nec es sary, cru ci bles may be boiled with 20%,HNO3 be fore use. Heat plat i num cru ci bles un til red,hot and boil with 50% (v/v) HCl prior to use. Ash,prod ucts with a high fat con tent (340%), e.g.,mar ga rine or lard, with great care to avoid,self-ig ni tion. Pre-ash such prod ucts ac cord ing to,D(c)(2), even if a pro gram ma ble fur nace is used.,A. Prin ci ple,Test por tions are dried and then ashed at 450°C un der a grad ual,in crease (￡50°C/h) in tem per a ture. 6M HCl (1 + 1) is added, and,the so lu tion is evap o rated to dry ness. The res i due is dis solved in,0.1M HNO3, and the analytes are de ter mined by flame and,graph ite furnace pro ce dures.,Table 999.11A. Interlaboratory study re sults for lead, cad mium, cop per, iron, and zinc in foods,Metal Sam ple,Analyte,range Mean, mg/kg na sr,b sR,c RSDr,d RSDR,e,rf Rg HorRat,Pb-GFAAS Liver paste/milk pow der 30.04 0.040 11 0.019 0.019 46 46 0.052 0.052 1.79,Ap ple sauce 0.27 10 0.10 38 0.29 1.97,Minced fish 0.53 10 0.11 20 0.31 1.14,Wheat bran 0.111 12 0.056 50 0.16 2.26,Sim u lated di ets D/E 0.246 10[1] 0.034 0.048 14 20 0.096 0.14 1.02,Cd-GFAAS Liver paste 30.05 0.0491 11 0.0058 12 0.016 0.48,Minced fish/wheat bran 0.175 8[1] 0.021 0.032 12 18 0.058 0.089 0.87,Sim u lated di ets D/E 0.51 8 0.10 0.13 19 26 0.27 0.37 1.48,Zn-FAAS Liver paste/minced fish 30.7 6.63 13 0.35 0.50 5.3 7.5 0.98 1.4 0.63,Ap ple sauce 0.699 11[3] 0.047 6.8 0.13 0.41,Wheat bran 71.5 12[2] 4.9 6.8 14 0.81,Milk pow der 35.0 12[2] 2.8 8.0 7.9 0.86,Sim u lated di ets D/E 37.82 11[2] 0.68 1.31 1.8 3.5 1.9 3.7 0.38,Cu-FAAS Ap ple sauce/minced fish 30.2 0.240 12[1] 0.076 0.076 32 32 0.21 0.21 1.63,Milk pow der 0.51 14[2] 0.23 45 0.65 2.56,Liver paste 5.34 13[2] 0.37 6.9 1.0 0.56,Wheat bran 9.52 12 0.98 10 2.7 0.88,Sim u lated di ets D/E 45.4 12[1] 1.6 3.1 3.6 6.9 4.6 8.8 0.77,Fe-FAAS Liver paste 34 24.3 14 2.8 11 7.8 1.12,Minced fish/milk pow der 3.99 11[3] 0.44 0.54 11 14 1.2 1.5 1.08,Wheat bran 124 13[1] 14 11 39 1.43,Sim u lated di ets D/E 216 13 18 23 8.2 11 49 64 1.55,a n = Number of laboratories remaining after elimination of outliers in brackets.,b sr = Repeatability standard deviation.,c sR = Reproducibility stan dard de vi a tion.,d RSDr = Relative repeatability standard deviation.,e RSDR = Relative reproducibility standard deviation.,f r = 2.8 ′ sr.,g R = 2.8 ′ sR.,2006 AOAC INTERNATIONAL,B. Apparatus,(a) Atomic ab sorp tion spectrophotometer.—With an,air–acet y lene burner or ni trous ox ide–acet y lene burner for,flame and a graph ite fur nace for electrothermal de ter mi na tions,with ap pro pri ate back ground (nonatomic) cor rec tion (see,Ta ble 999.11B).,See Ta ble 999.11C for ex am ple of in stru men tal pa ram e ters for,graph ite fur nace AAS. (The pa ram e ters listed are for a Perkin Elmer,HGA-500 in stru ment. For other in stru ments, the pa ram e ters may,have to be changed. Suit able pa ram e ters are usu ally given in the,man ual pro vided with the in stru ment.),(b) Lamps.—Hollow cathode or electrodeless dis charge lamps for all,elements determined.,(c) Furnace.—Programmable, or muf fle furnace with thermostat,maintaining 450° ± 25°C. If muf fle fur nace is used, a sep a rate pre-ashing,de vice is re quired. See (d)–(h).,(d) Hot plate.—With heat ing con trol, to heat up to about 300°C.,(e) Lamp.—IR 250 W, fixed to a re tort stand in a way that al lows,ad just ment of the dis tance to the hot plate.,(f) Ceramic plate.—e.g., Des ic ca tor plate on a low stand, with a,di am e ter that suits the hot plate.,(g) Glass cover.—e.g., Crys tal lizing dish, 185 mm di am e ter, 100 mm,height, to fit on (f) or equiv a lent.,(h) Wash-bottle.—“Scrubber,” containing H2SO4 for purification of,air.,See Fig ure 999.11 for as sem bly of items (d)–(h).,(i) Quartz or platinum crucibles……
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