AOAC Official Method aoac5.3.14a
|
ID： |
9F15B34B3ECA4D6EA2BDC1DD0FCD88E4 |
|
文件大小(MB)： |
0.06 |
|
页数： |
4 |
|
文件格式： |
|
|
日期： |
2024-7-30 |
|
购买： |
文本摘录（文本识别可能有误，但文件阅览显示及打印正常，pdf文件可进行文字搜索定位）：
5.3.14A,AOAC Official Method 997.04,Monensin in Premix and Animal Feeds,Liquid Chromatographic Method,First Action 1997,(Suitable for determination of monensin in range of,5–200 000 mg/kg in all types of premixes and animal feeds.),See Table 997.04 for the results of the interlaboratory study supporting,acceptance of the method.,A. Principle,Monensin is extracted from premixes and feeds with methanol–,water (90 + 10, v/v) and isolated by liquid chromatography,with post-column derivatization. Acid-reaction product of,monensin with vanillin is measured by variable wavelength detector,at 520 nm. There is no interference from narasin, salinomycin, and,lasalocid.,B. Apparatus,(a) Liquid chromatograph (LC).—With recorder or integrator,(manual or computer), pulse-dampened LC pump [for LC mobile,phase, C(g)] and reagent pump [for vanillin reagent, C(h)] both operating,at 0.7 mL/min; variable wavelength absorbance detector operating,at 520 nm with rise time of 1.0 and range of 0.2 (or as,needed); 90° Tee positioned in such way so inlet flows directly oppose,one another; and stainless steel coil (6.1 m ′ 0.51 mm id) enclosed,in 98.0°C heater. (Comparable components may be,substituted. Parameters may be modified to compensate for daily,variations in instrument performance.),Operating conditions: injection volume, 200 mL; column temperature,ambient; reaction coil temperature, 98°C; flow rate (both,pumps), 0.7 mL/min. Approximate retention times: monensin A,640 s; monensin B, 560 s; monensin C/D, 730 s (see Figure 997.04A,for chromatogram of typical system suitability test, Figure 997.04B,for chromatogram of rumensin medicated article, and Figure 997.04C,for chromatogram of monensin medicated feed.),(Note: When not using system for 2–3 days, or at regular intervals,during use periods, flush system with methanol to prolong life of,components.),(b) LC column.—250 ′ 4.6 mm id (Whatman Partisil 5 ODS-3,or equivalent). C18 guard column may be used to extend life of analytical,column.,(c) LC vials.,(d) Mechanical shaker.—Wrist action shaker, or equivalent.,(e) Filter.—0.2–0.5 mm porosity; Teflon or chemical resistant.,(f) Containers.—500–1000 mL, glass or polypropylene.,(g) Volumetric flasks.—100 and 200 mL.,(h) Magnetic stirrer.,(i) Teflon-coated stir bars.,(j) Feed grinder.—Centrifugal grinding mill with 3mmscreen.,(k) Feed mixer.,(l) Balances.—(1) Top loading and (2) analytical.,C. Reagents,(a) Solvent.—Methanol, LC grade.,(b) Purified H2O.—e.g., LC grade.,(c) Sulfuric acid.—Analytical grade.,(d) Glacial acetic acid.—ACS grade.,(e) Vanillin.—99% purity.,(f) Neutralized methanol.—Add 1 g NaHCO3 to 4 L methanol.,Mix well and, if needed, filter through 11 mmpore size filter paper.,(g) LC mobile phase.—Methanol–H2O–glacial acetic acid solution,(94 + 6 + 0.1, v/v/v). Degas with He prior to use.,(h) Vanillin reagent.—Methanol–sulfuric acid–vanillin solution,(95 + 2 + 3, v/v/w). While stirring gently, add slowly and carefully,20 mL concentrated H2SO4 to 950 mL methanol, C(a). (Caution:,Avoid splattering when adding H2SO4 to methanol, using pipet or,other suitable equipment. Do not add H2SO4 to methanol by pouring,from beaker or graduated cylinder.) Let methanol–H2SO4 solution,cool to room temperature. Add 30.0 g vanillin while stirring gently.,Vanillin reagent is stable up to 4 weeks at room temperature in dark,amber or foil-covered container.,(i) Extraction solution.—Methanol–H2Osolution (90 + 10, v/v).,(j) Monensin standard solutions.—(1) Monensin standard stock,solution.—1 mg/mL. Accurately weigh 100 mg monensin reference,standard (available from Eli Lilly and Company, Lilly Corporate Center,Indianapolis, IN 46285, USA) into 100 mL volumetric flask and,dilute to volume with methanol,C(a). (2) Monensin working standard,solutions.—(i) For rations with theoretical monensin concentrations,>40 ppm. Quantitatively dilute monensin standard stock solution with,extraction solution to obtain monensin concentrations of 5.0, 10.0,20.0, and 40.0 mg/mL. (ii) For rations with theoretical monensin concentrations,<40 ppm. Quantitatively dilute monensin standard stock,solution with extraction solution to obtain monensin concentrations of,0.25, 1.25, 2.5, 3.75, and 5.0 mg/mL.,Monensin standard solutions are stable up to 4 weeks in refrigerator,or at room temperature protected from direct sunlight.,. 2002 AOAC INTERNATIONAL,Table 997.04 Interlaboratory study results for determination of monensin in premixes and animal feed by liquid chromatography,with post-column derivatization,Sample Mean Monensin sr sR RSDr, % RSDR, % r R,Coban premix 130.2 mg/g 132 mg/g 3.6 2.8 10,Rumensin premix 190.3 mg/g 176 mg/g 6.5 3.4 1……
……