AOAC Official Method 991
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03304B7115784FCDA6D243B60F9D595B |
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0.06 |
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页数： |
7 |
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日期： |
2024-7-30 |
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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）：
10.3.05,AOAC Official Method 991.07,Nitrogen- and Phosphorus-Containing Pesticides,in Finished Drinking Water,Gas Chromatographic Method,First Action 1991,Final Action 1993,(Applicable to determination of 44 nitrogen- or phosphorus-,containing pesticides in finished drinking water.),Interlaboratory Study Results:,Collaborative study showed method acceptable for all analytes,tested except merphos, which thermally decomposed in GC injection,port. Matrix effects were statistically significant for 5 compounds,(carboxin, disulfoton, metolachlor, pronamide, and,simazine) in finished drinking water. In reagent water, RSDR for,44 pesticides range from 12.8 to 25.4%, and exceeded 25% only for,vernolate (25.4%). In finished drinking water, RSDR for 44 pesticides,ranged from 11.5 to 42.6%, and exceeded 25% for tricyclazole,(25.1%), terbufos (25.8%), fluridone (28.1%), terbutryn (29.1%),disulfoton (32.5%), and carboxin (42.6%). See Table 991.07A for,the results of the interlaboratory study supporting acceptance of,method.,A. Principle,Measured volume of test portion (1 L) is extracted withCH2Cl2 by,shaking in separatory funnel or by mechanical tumbling in bottle.,CH2Cl2 extract is separated, dried with anhydrous Na2SO4, solvent-,exchanged with methyl tert-butyl ether (MTBE), and concentrated,to 5 mL. Pesticides are separated and measured by capillary,column gas chromatography using a nitrogen–phosphorus detector.,Estimated method detection limits range from 0.075 mg/L for,simazine to 5.0 mg/L for mevinphos; estimated method detection,limits for 36 pesticides range from 0.13 to 1.0 mg/L.,B. Apparatus,(a) Grab laboratory samples bottles.—1000 mL, borosilicate,glass with TFE-fluorocarbon-lined screw caps (Wheaton Media/,Lab bottle No. 219820 meets these specifications). Extract liners,overnight with methanol before use.,(b) Separatory funnel.—2000 mL, borosilicate glass with,TFE-fluorocarbon stopcock and ground-glass or TFE-fluorocarbon,stopper.,(c) Tumbler bottle.—1.7 L, low extractable borosilicate glass,with TFE-fluorocarbon-lined screw caps (Wheaton Roller Culture,Vessel No. 348273 meets these specifications). Cut liners to fit,screw cap from TFE-fluorocarbon sheets (Pierce No. 012736,meets these specifications); extract liners overnight with methanol,before use.,(d) Kuderna–Danish (K–D) apparatus.—(1) Concentrator,tube.—10 or 25 mL, borosilicate glass, graduated, standard,taper 19/22 . Check calibration of concentrator tube at volumes used,in method. Use ground-glass stoppers to prevent evaporation of extracts.,(2) Evaporation flask.—500 mL, borosilicate glass, standard,taper 24/40 top, standard taper 19/22 bottom, capable of attachment,to concentrator tube with springs. (3) Snyder columns.—3-ball,macro, 218 mm, standard taper 24/40 or 2-ball micro, 170 mm, standard,taper 19/22.,( e ) V i a l s . — G l a s s , 5 t o 1 0 mL c a p a c i t y , w i t h,TFE-fluorocarbon-lined screw caps.,(f) Separatory funnel shaker.—(Optional.) Capable of holding,2-L separatory funnels and shaking them with rocking motion,to thoroughly mix funnel contents (Eberbach Co., Ann Arbor, MI,USA, or other suppliers).,( g ) T u m b l e r . —Capable of holding tumbler bottles,end-over-end at 30 rpm (Associated Design and Manufacturing,Co., Alexandria, VA USA, meets these specifications).,(h) Boiling stones.—Carborundum, No. 12 granules. Heat,30 min at 400°C before use. Cool and store in desiccator.,(i) Water bath.—Heated, capable of control±2°C. Use bath in hood.,(j) Balance.—Analytical, capable of accurately weighing to,nearest 0.0001 g.,(k) Gas chromatograph.—Temperature-programmable system,for use with capillary columns, including syringes, analytical,columns, gases, detector, and strip chart recorder. Data system is,recommended for measuring peak areas. Primary column: 30 m ′,0.25 mm id DB-5 fused-silica capillary column, 0.25 mm film,thickness (J&W Scientific, Inc., meets these specifications). Confirmation,column: 30 m ′0.25 mm id DB-1701 fused-silica capillary,column, 0.25 mm film thickness (J&W Scientific, Inc., meets,these specifications). Operating conditions: injection volume,2 mL splitless with 45 s delay; He carrier gas at 30 cm/s linear velocity;,injector 250°C; detector 300°C; oven programmed from,60–300°C at 4°C/min; nitrogen–hosphorus detector.,C. Reagents,(a) Standard solutions.—Use standards of test compounds (Table,991.07B) with purity >96% to prepare stock solutions at 1 mg/mL in,MTBE. Commercially prepared stock standards may be used at any,concentration if they are certified by manufacturer or independent,source. Store solutions at room temperature and protect from light.,Replace stock solut……
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