AOAC Official Method 975
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76FF81029C2644BEBC593DFE840B3F10 |
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0.08 |
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2 |
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日期： |
2016-2-28 |
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45.1.25,AOAC Of fi cial Method 975.43,RRR- or all-rac-alpha-Tocopherol,in Drugs and Food or Feed Sup ple ments,Polarimetric Method,First Ac tion 1975,Fi nal Ac tion 1980,Ap pli ca ble to phar ma ceu ti cal prep a ra tions and food or feed,sup ple ments con tain ing a-tocopherol es ters if the a-tocopherol is,pres ent at or can be con cen trated to 3200 mg a-tocopherol/g be fore,ox i da tion step.,A. Prin ci ple,To cal cu late vi ta min E in In ter na tional Units (IU), it is nec es sary,to know or to iden tify a-tocopherol or a-tocopherol es ter as RRR or,all-rac form. Product is ex tracted and saponified, and ex tra ne ous,color is re moved by chro ma tog ra phy. Op ti cal ro ta tion of,ferri cyanide ox i da tion prod uct of re sult ing a-tocopherol is,neg li gi ble for all-rac forms and pos i tive for RRR form.,Pre cau tions.—See 971.30A (see 45.1.24).,B. Apparatus,See 971.30B(a) and (j) (see 45.1.24), and fol low ing:,High pre ci sion polarimeter.—Read ing to ￡0.002° (Rudolph,Instruments, 40 Pier Ln, Fairfield, NJ 07004-4576, USA,www.rudolphin st.com, or equiv a lent); with 2.8 mL semimicro glass,tube, 4.0 mm bore, 20 cm long, and cen tral tubulation.,C. Re agents,See 971.30C (see 45.1.24) and fol low ing:,(a) Magnesium sil i cate.—Florisil grade 60–100 mesh (Aldrich,Cat. No. 220752, or equivalent).,(b) Pe tro leum ether–ether mix ture.—Di lute 200 mL an hy drous,ether, 971.30C(f) (see 45.1.24), to 1 L with pe tro leum ether,971.30C(a)(1) (see 45.1.24).,(c) Isooctane.—ACS UV grade.,(d) Po tas sium ferri cyanide so lu tion.—Dis solve 5.0 g,K3Fe(CN)6 in 50 mL 0.2M NaOH. (Cau tion: Avoid re sid ual ac e tone,on glass ware. If so lu tion is brown, dis card.),D. Prepa ration of Test Portion and Extrac tion,See 971.30D (see 45.1.24) and fol low ing:,(a) Oily forms.—Weigh test por tion con tain ing 100–120 IU,vi ta min E and place in stan dard taper 125 mL round-bottom flask.,Saponify as in E.,(b) Dry forms and hard-shell mul ti vi ta min cap sules.—(If,nec es sary, grind in mor tar to fine pow der.) Place ac cu rately weighed,test por tion of dry prod uct or cap sule con tents con tain ing,100–120 IU vi ta min E in stan dard taper flask and add 50 mL 1.25M,H2SO4. At tach re flux con denser and re flux 30 min on hot plate. Cool,to room tem per a ture and trans fer to sep a ra tor, rins ing flask with,50 mL ab so lute al co hol. Ex tract with two 75 mL and one 50 mL,por tions high boil ing pe tro leum ether, 971.30C(a)(2) (see 45.1.24).,Com bine pe tro leum ether ex tracts, and evap o rate un der N2 to,<50 mL. Trans fer to stan dard taper 125 mL round-bottom flask and,evap o rate sol vent un der N2 on steam bath. Saponify as in E.,(c) Soft-shelled mul ti vi ta min cap sules.—(1) Prep a ra tion of,col umn.—Place in or der, on top of small glass wool plug in,chro mato graphic tube: 3 g fuller’s earth, 3 g Ce(HSO4)4-treated,fuller’s earth, 3 mm layer fuller’s earth, 3 g Ce(HSO4)4-treated,fuller’s earth, 4 g fuller’s earth, and 5 mm layer diatomaceous earth,on top. Tap gently af ter ad di tion of each por tion of ad sor bent to,en sure even pack ing. Wash col umn un der suc tion with ca 200 mL,pe tro leum ether, 971.30C(a)(1) (see 45.1.24). Keep layer of sol vent,above top of ad sor bent at all times. Use new col umn for each as say.,(2) Elu tion of vi ta min E.—Weigh test por tion of cap sule con tents,con tain ing 100–120 IU vi ta min E, dis solve in 4 mL pe tro leum ether,971.30C(a)(1) (see 45.1.24), and quan ti ta tively trans fer to top of,chro mato graphic col umn, us ing elon gated drop per. If aliquot,con tains <500 mg lipid, add ol ive oil as nec es sary to give this,min i mum amount lipid. Use five ca 1.0 mL por tions pe tro leum ether,971.30C(a)(1) (see 45.1.24), as rinses for quan ti ta tive trans fer. To,pre vent col umn from run ning dry, do not use vac uum dur ing,trans fer. Elute col umn with 100 mL ben zene. Evap o rate ben zene,eluate to ca 4 mL on steam bath un der N2 stream and then to dry ness,un der N2 with re duced heat. Saponify as in E.,E. Saponification and Re-Extraction,Pro ceed as in 971.30E (see 45.1.24). Use 0.2 mL of this ether,so lu tion to de ter mine a-tocopherol as in F(a) or (b), and pu rify,re main der as in G.,F. Determina tion of alpha-Tocopherol,(a) By colorimetry.—Pro ceed as in 971.30G(b) (see 45.1.24).,Cal cu late as fol lows:,mg a-Tocopherol equiv a lent/test por tion =,mg a-tocopherol mea sured ′ (d/e) ′ (1/1000),where d = to tal mL unsaponifiable ex tract, e = mL of d used for,colorimetric read ing, and (1/1000) = fac tor to con vert mg to mg.,(b) By gas chro ma tog ra phy.—Pro ceed as in 969.40 (see,45.1.29). De ter mine mg a-tocopherol……
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