AOAC Official Surplus Method 958
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FB5F6DFEF5534638AFE25F8F3F00007B |
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0.03 |
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3 |
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日期： |
2024-7-30 |
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10.6.09,AOAC Official Surplus Method 958.08i,p-Chlorophenyl Phenyl Sulfone,Pesticide Residue,Spectrophotometric Method,Final Action 1965,Surplus 1969,11th ed.,29.075 Principles,Tech. grade Sulphenone contains ca 80% pchlorophenyl,phenyl sulfone (p-CIDPS); the remainder,consists almost entirely of related sulfones, bis(pchlorophenyl),sulfone (p,pN-CIDPS) and diphenyl,sulfone (DPS).,Hexane strip solns are extd with CH CN 3,which seps Sulphenone components from bulk of,waxes, coloring matter, and to some extent from other,pesticides. The CH CN residue is chromatographed on 3,Magnesol column with hexane-anhyd. ether. The,residue of fraction contg p-CIDPS is dissolved in,isooctane for detn of UV A.,Magnesol column seps p,pN-CIDPS,p-CIDPS, and DPS in that order. DDT, TDE,methoxychlor, and other highly absorbing pesticides are,eluted within threshold vol. for p-CIDPS. A few,pesticides (phenothiazine and malathion), when present,in amts well over their tolerances, show slight,interference.,29.076 Apparatus,(a) Chromatographic tube.—Std wall Pyrex,glass tubing 2.5 cm od × 60 cm long ending in ca 45E,taper sealed to stopcock with 2 mm bore. Seal medium,porosity fritted disk in place just above taper. Lubricate,stopcock with starch-glycerol gel or glycerol.,(b) Pressure source.—See 947.02i(a). Threeway,stopcock between column and pressure source,permits convenient release of pressure. Connect to,column with rubber stopper but avoid wetting stopper,with solvs.,(c) Solvent evaporator.—Bent glass tubes in,support, connected to filtered air source.,(d) Spectrophotometer.—Suitable for,measuring A between 230 and 260 nm; with 2 matched,1 cm cells.,(e) Glassware.—Avoid contamination, taking,special care with flasks for receiving chromatgc,fractions. Rinse successively in small groups with,acetone and follow with $3 rinsings with hexane or,isooctane, according to use. All acetone must be,removed. Clean heavily contaminated glassware with,chromic acid cleaning soln followed by thoro rinsing,and drying.,29.077 Reagents,(a) Hexane.—Bp 60–70E (Skellysolve B or,equiv.).,(b) Isooctane.—Pure grade, 2,2,4-,trimethylpentane (Phillips Petroleum Co., or Enjay Co.,Inc., 60 W. 49th St, New York, NY 10020). A at 230,240, and 250 nm against H O should be #0.100; 2,otherwise purify by shaking 15 min with 5 g silica gel,(28–200 mesh) for each 100 mL in g-s bottle. Keep in,dark; filter when needed. Sample and std A are detd,against isooctane blank. Solv. in both cells must be,from same batch of filtered solv.,(c) Ethyl ether, anhydrous.—(Mallinckrodt A.,R. or equiv.). Evap. 20 mL at 40–50E and dissolve,residue in 20 mL isooctane. A at 230, 240, and 250 nm,against isooctane should be #0.020. Differential A, A240,— 0.5 (A + A ), should be #±0.003. 230 250,(d) Hexane-ether solvent mixture.—Distill,hexane, rejecting first 5% and last 10%. Mix 700 mL,hexane with 300 mL anhyd. ether. Store in g-s bottle.,(e) Acetonitrile.—Practical grade.,(f) Magnesol.—Industrial regular grade (FMC,Corp., Inorganic Chemicals Div., 633 3rd Ave, New,York, NY 10017). Mix bath by tumbling in large jar.,Keep in small, tightly closed containers.,(g) Sulphenone std soln.—0.5 mg/mL.,Dissolve 50 mg tech. grade Sulphenone (Stauffer,Chemical Co., Richmond Research Lab., Richmond,CA 94804) in ca 60 mL hexane in 100 mL vol. flask on,steam bath, cool, and dil. to vol.,(h) p-Chlorophenyl phenyl sulfone (p-,CIDPS).—Suitable for std (Stauffer Chemical Co.).,29.078 Standardization of Chromatographic,Column,(Caution: See Appendix B: Laboratory Safety,Safety Techniques and Practices, pipets; Special,Chemical Hazards, pesticides.),Pipet 1 mL (0.5 mg) Sulphenone std soln into,125 mL Phillips conical beaker and evap to dryness,with gentle air current. Add 5 mL hexane-ether solv. to,residue. Form close-fitting metal foil cover over top of,beaker, warm to ca 45E, swirl to insure soln, and set,aside while prepg chromatgc column.,Clamp chromatgc tube in ring stand, in vertical,position, and place 100 mL graduated cylinder under,outlet. Pour 25 mL hexane-ether solv. into tube, add desired, using less Magnesol. If column is satisfactory,15.0 g Magnesol thru powder funnel, and wash down det. A of remaining fractions contg p-CIDPS. Det. A of,tube walls with 50 mL hexane-ether. Stir thoroly with trailing fractions at 242 and 234 nm (DPS max.) to,glass rod until no more bubbles rise and mixt. is locate final fraction for p-CIDPS.,uniform; remove rod and let settle ca 1 min. Loosen Note 1.—First few fractions normally show,clamp holding tube and tap end on folded towel while little A; considerable A in these fractions indicates,slowly rotating tube back and forth to……
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