AOAC Official Surplus Method 961
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9194EDF5A3F34FA4995379E08FD4EC00 |
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0.03 |
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2 |
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日期： |
2024-7-30 |
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10.6.01,AOAC Official Surplus Method 961.12i,Azinphos-Methyl,Pesticides Residues,Spectrophotometric Method,First action,Surplus 1974,12th ed.,(Applicable to cole-type crops and to apples, plums,peaches, grapes, apricots, and cherries. For cherries and,highly pigmented cole-type vegetables, carry recovery,run along with detn. "(Stop)" indicates points in method,where sample may be held for short period or overnight,without loss.),29.102 Principle,Guthion is extd from crop with acetone and reextd,with CHCl from acetone after diln with H O. Solv. is 3 2,removed by evapn; residue is dissolved in isopropanol,and cleaned up on chromatgc column. Guthion is,hydrolyzed in alk. soln to anthranilic acid, which is,diazotized and coupled with N-(1-naphthyl)-,ethylenediamine.2HCl to form colored compd.,Omission of alk. hydrolysis reveals presence of,interfering materials except Et homolog of Guthion.,29.103 Reagents,(a) Potassium hydroxide in isopropanol soln.—0.5N.,Dissolve 28.5 KOH in absolute (99.5%) isopropanol.,(b) Alumina.—Acid-wash 0.5 lb Merck chromatgc,grade Al O in 1 L flask by addig 40 mL H O and 2.5 2 3 2,mL HCl and mixing thoroly. Let stand 2 hr. wash by,decantation 4 times with H O, filter thru buchner, and 2,wash until filtrate is only faintly acid. Finally wash with,two 200 mL portions alcohol, evap. last traces of,alcohol on steam bath, and dry in oven at 140E,overnight. Store in tightly closed container or,desiccator.,(c) Ammonium sulfamate soln.—2.5%. Prep. every 3,days.,(d) Guthion std soln.—80 μg/mL. Dissolve 80 mg,Guthion (available from Chemagro Division of,Baychem Corp., PO Box 4913, Kansas City, MO,64120) in acetone and dil. to 100 mL with acetone. Dil.,10 mL to 100 mL with acetone. (Caution: Guthion is,extremely poisonous. Avoid contact with skin and,inhalation of dust.),(e) Coupling reagent.—1% soln of N-(1-,naphthyl)ethylenediamine.2HCl. Prep. every 3 days.,(f) Magnesium oxide.—Adsorptive magnesia, Fisher,Scientific Co. No. S-120.,(g) Sodium nitrate soln.—0.2%. Prep. fresh daily.,29.104 Preparation of Sample,(Caution: See Appendix B: Laboratory Safety,Equipment, blenders; Organic Solvents, flammable,solvents; Special Chemical hazards, acetone.),Remove stems, stones, or pits from fruits. Chop,sample into small pieces, using Hobart food cutter, or,equiv., and weigh 200 g sample into high-speed,blender. Blend at speed 5 min with 200 mL acetone.,Add 200 mL addnl acetone and blend 5 min at low,speed. Cool to room temp. and transfer to 1 L graduate,with dil. acetone (2 + 1). Dil. to 700 mL with dil.,acetone (2 + 1) and mix. Filter thru plug of glass wool,in funnel. Refilter thru same plug, if necessary, to,obtain clear filtrate. (Stop),29.105 Purification,(Caution: See Appendix B: Laboratory Safety,Equipment, distillation, extraction and evaporation;,Organic Solvents, toxic solvents; Special Chemical,hazards, chloroform.),Place 350 mL clear filtrate in 1 L separator, add 3.0,mL HCl and 300 mL H O, and mix. Add 100 mL 2,CHCl and shake gently 1 min. Let sep., and drain 3,CHCl thru column contg 100 g anhyd. Na SO , 3 24,collecting filtrate in 600 mL beaker. Ext with 6 addnl,50 mL portions CHCl , avoiding emulsions. Filter each 3,portion with suction thru Na SO column to remove 2 4,droplets of H O. Evap. combined CHCl exts to dryness 2 3,on steam bath in air current.,Prep. 2 × 40 cm column with fritted glass plate contg,successive layers of 2 g Hyflo Super-Cell, 5 g well,mixed mixt. of 2 parts Super-Cel and 1 part MgO, 10 g,Al O , and 20 g anhyd. Na SO . Add each layer under 2 3 2 4,suction and after each layer is added, remove suction,and tamp on wood block to liberate trapped air.,Equilibrate column with 50 mL isopropanol.,Dissolve residue from CHCl extn in 25 mL 3,isopropanol, boiling if necessary. Cool and pour sample,soln onto column as last of equilibrating solv. passes,into top layer of column. Rinse beaker with 25 mL,isopropanol and transfer to column. Collect 20 mL,isopropanol eluate, using suction to maintain flow.,(Stop),29.106 Determination,Evap. eluate or aliquot to dryness on steam bath in air,current and remove from bath. (Stop) Dry residue 30,min in 50–60E oven. Dissolve dry residue in 10 mL,benzene, add 10 mL alc. 0.5N KOH, (a), and mix. After,20 min, acidify with 8 mL 3N HCl. Transfer mixt. to,250 mL separator, using 15 mL H O and 50 mL 2,benzene to rinse beaker. Shake vigorously 1 min. let,sep., and drain aq. layer into 50 mL g-s graduate. Rinse,beaker with addnl 15 mL H O, transfer to separator, 2,shake vigorously, and let sep. Drain aq. layer into,graduate and discard benzene layer.,Dil. aq. soln to 50 mL with H O and mix. Add 0.2 g 2,Zn dust and le……
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