AOAC Official Surplus Method 959
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F81C9AEA60254BEDAF9BF077A8C7B5DC |
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0.03 |
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2 |
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日期： |
2024-7-30 |
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10.6.05,AOAC Official Surplus Method 959.10i,2-(p-tert--Butylphenoxyl)-,1-Methylethyl 2-Chloroethyl Sulfite,(Aramite) Pesticide Residues,Colormetric Method,Final Action 1965,Surplus 1975,12th ed.,29.067 Principle,Aramite is stripped from sample with benzene,soln is concd, and Aramite is hydrolyzed with KOHisopropanol,to form ethylene oxide. Evolved ethylene,oxide is converted to HCHO with KIO , and HCHO is 4,reacted with acetylacetone to form colored compd.,29.068 Reagents,(a) Isopropanol.—Redistil and store over anhyd.,Na SO . 2 4,(b) Periodic acid soln.—Dissolve 0.5 g,HIO .2H O in H O and dil. to 100 mL with H O. Dil. 1 4 2 2 2,vol. with 2 vols 0.1N HCl.,(c) Sodium arsenite soln.—Dissolve 2 g,Na AsO in H O and dil. to 100 mL with H O. 2 2 2 2,(d) Acetylacetone reagent.—Dissolve 25 g,NH OAc in H O, add 3 mL HOAc and 0.2 mL redistd 4 2,acetylacetone, and dil. to 100 mL with H O. 2,(e) Aramite std solns.—(1) Stock soln.—ca 5,mg/mL. Accurately weigh ca 250 mg (ca 0.25 mL) std,Aramite (available from Uniroyal Chemical), dissolve,in benzene, and dil. with benzene to 50 mL. (2),Intermediate soln.—50 μg/mL. Dil. aliquot of stock,soln contg 5 mg to 100 mL with benzene. (3) Working,solns.—Dil. aliquots of intermediate soln with benzene,to obtain lower concns. Solns as dil. as 10 or 25 μg/mL,remain unchanged 2–3 weeks. Store std solns in,refrigerator.,29.069 Isolation Apparatus,Lead air or N at ca 1 lb pressure into surge tank,consisting of 2 L bottle fitted with inlet and outlet.,Connect outlet to 500 mL gas washing bottle contg,H SO , connected thru capillary bubble counter 2 4,(constructed from thermometer tubing) filled with light,mineral oil, and then to reaction tube (25 × 100 mm,over-all length with standard taper 19.22 joint) with gas,inlet tube equipped with inner standard taper 19.22 joint,to fit into reaction tube. Attached $80 mm 8 mm od,thinwall tubing above inlet before attachment to 2–5,mm id capillary delivery tube. (Gas inlet tube, Corning,Glass Works No. 96800, standard taper 19/38, may be,used by connecting a standard taper 19/38 inner joint to,capillary delivery tube.) Construct scrubber at lower,end of delivery tube with 4 expanded rings in 50 mm,which just fits inside 11 mm id test tube, upper portion,of which is enlarged to 16 mm id to increase its vol.,(See Fig. 29:07.),29.070 Preparation of Samples,(Caution: See Appendix B: Laboratory Safety,equipment, distillation, extraction and evaporation;,organic solvents, toxic solvents, flammable solvents;,special chemical hazards, benzene.),(a) Leafy vegetables.—Chop into small pieces.,Weigh 500 g into 2 qt (2 L) tumble jar, add 500 mL,benzene, and roll or tumble ca 10 min. Pour off solv.,sep. any H O, dry benzene with anhyd. Na SO , and 2 24,filter.,(b) Small fruits.—Weigh 500 g into 2 qt (2 L),tumble jar and strip with 500 mL benzene as ablve.,(c) Large fruits.—Weigh 10 whole fruits (1–2,kg) into 2 gal. (7.5 L) tumble jar, add 500 mL benzene,and roll or tumble ca 10 min. Pour off benzene, dry, and,filter as above.,29.071 Determination,(Caution: See Appendix B: Laboratory Safety,equipment, distillation, extraction and evaporation;,organic solvents, toxic solvents, flammable solvents;,special chemical hazards, benzene.),Conc. aliquot of filtered strip soln (100–400 mL),to 3 mL reaction tube. (Entire strip soln may be concd,in beaker under gentle air current and dild to definite,vol. (50 or 100 mL). Aliquots of this concn can then be,measured directly into reaction tube for final evapn to,3 mL. Soln must never be evapd to dryness.) Place premixed,reagent, (b), in scrubber. Use 3 mL for residues,<0.5 ppm or 5 mL for residues $0.5 ppm. (Two std,curves are required, 1 for 3 mL vol. in scrubber and,other for 5 mL.) To sample in reaction tube add 5 mL,isopropanol and 3 pellets KOH. Attach to app. without,delay.,Pass current of dry air or N thru gas inlet tube at,rate of 4–6 mL/min, and heat reaction tube, maintaining,gentle refluxing 30 min. Remove scrubber tube and,heat in 50E constant temp. bath 15 min. Cool to room,temp. Pipet 2 mL into small test tube, add 0.5 mL 2%,NaAsO , let stand for moment, shake, and let stand 2,until colorless. Add 0.5 mL acetylacetone reagent, mix,and heat in boiling H O or live steam 6 min. Remove 2,from heat and let stand $10 min in air. Cool to room,temp., transfer to cell, and det. A at 412 nm. Color is,stable for $2 hr. Det. μg from std curve, and calc. to,ppm.,Prep. std curve by measuring vols of std soln,contg 0–150 μg into reaction tube with enough benzene,to total 3 mL, and carry thru entire detn as for samples.,Plot A against μg Aramite.,FIG. 29:07—Apparatus for determining Aramite,(1……
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