《美国FDA农残分析手册》（第一卷英文版）Chapter 4 Selective MRMs.pdf_大学文库

Pesticide Analytical Manual Vol. I SECTION 401 401: METHOD FOR N-METHYLCARBAMATES BASIC REFERENCES Krause, RT(1979). Chromatogr. 185, 615-624 Krause, RT(1980)). Assoc. Off. Anal. Chem. 63, 1114-1124 Krause, RT.(1985)/. Assoc. Of Anal. Chem. 68, 734-741 GENERAL PRINCIPLES N-methylcarbamate insecticide residues, including carbamate metabolites, are ex- tracted with methanol. The extract is cleaned up by partitioning and column chromatography on a charcoal/Celite column. Residues are selectively determined with an HPLC system consisting of a reverse phase (RP)column, post-column hydrolysis and derivatization, and detection of the resultant derivative with a fluo- rescence detector Variations in the determinative step may be used for additional residues not of the N-methylcarbamate structure APPLICABILITY Consult Guide to PAM I for additional information pertinent to the appropriate application of multiresidue methodology Method is applicable to residues with an N-methylcarbamate structure in either nonfatty or fatty foods when determinative step includes post-column hydrolysis and derivatization. See Table 401-a, following method description, for chemicals tested through the method Method is applicable to naturally fluorescent residues when post-column hydrolysis and derivatization are not performed. See Table 401-b, following Table 401-a. Certain commodities, e.g., oranges, contain naturally fluorescent co-extractives that interfere with analysis. Limit of quantitation is 0.01 ppm carbofuran in high moisture products(fresh fruits and vegetables)and about 0. 02 ppm in dry products REFERENCE STANDARDS Dissolve reference standards of N-methylcarbamates in methanol to produce con- entrations of l ug/ mL. Store solutions in actinic glassware, and keep in refrigera- tor when not in use. Most carbamate standards stored in this manner are stable fo several months. However, methiocarb sulfone and sulfoxide degrade within hours and days, respectively, even with stated storage precautions STEPS OF THE METHOD Extraction E) Recommended use El (p. 401-3) Extraction with methanol high moisture products E2(P 401-4) Extraction with methanol, reduced low moisture products le size Cleanup(C) Cl (P 401-5) Two stage liquid-liquid pa artitioning products and charcoal/Celite column cleanup

Transmittal No. 94-1 (1/94) Form FDA 2905a (6/92) 401–1 Pesticide Analytical Manual Vol. I SECTION 401 401: METHOD FOR N-METHYLCARBAMATES BASIC REFERENCES Krause, R.T. (1979) J. Chromatogr. 185, 615-624 Krause, R.T. (1980) J. Assoc. Off. Anal. Chem. 63, 1114-1124 Krause, R.T. (1985) J. Assoc. Off. Anal. Chem. 68, 734-741 GENERAL PRINCIPLES N-methylcarbamate insecticide residues, including carbamate metabolites, are extracted with methanol. The extract is cleaned up by partitioning and column chromatography on a charcoal/Celite column. Residues are selectively determined with an HPLC system consisting of a reverse phase (RP) column, post-column hydrolysis and derivatization, and detection of the resultant derivative with a fluorescence detector. Variations in the determinative step may be used for additional residues not of the N-methylcarbamate structure. APPLICABILITY Consult Guide to PAM I for additional information pertinent to the appropriate application of multiresidue methodology. Method is applicable to residues with an N-methylcarbamate structure in either nonfatty or fatty foods when determinative step includes post-column hydrolysis and derivatization. See Table 401-a, following method description, for chemicals tested through the method. Method is applicable to naturally fluorescent residues when post-column hydrolysis and derivatization are not performed. See Table 401-b, following Table 401-a. Certain commodities, e.g., oranges, contain naturally fluorescent co-extractives that interfere with analysis. Limit of quantitation is 0.01 ppm carbofuran in high moisture products (fresh fruits and vegetables) and about 0.02 ppm in dry products. REFERENCE STANDARDS Dissolve reference standards of N-methylcarbamates in methanol to produce concentrations of 1 µg/mL. Store solutions in actinic glassware, and keep in refrigerator when not in use. Most carbamate standards stored in this manner are stable for several months. However, methiocarb sulfone and sulfoxide degrade within hours and days, respectively, even with stated storage precautions. STEPS OF THE METHOD Extraction (E) Recommended Use E1 (p. 401-3) Extraction with methanol high moisture products E2 (p. 401-4) Extraction with methanol, reduced low moisture products sample size Cleanup (C) C1 (p. 401-5) Two stage liquid-liquid partitioning all products and charcoal/Celite column cleanup

Transmittal No. 94-1 (1/94) Form FDA 2905a (6/92) 401–3 Pesticide Analytical Manual Vol. I SECTION 401 E1 EXTRACTION WITH METHANOL Reference Krause, R.T. (1980) J. Assoc. Off. Anal. Chem. 63, 1114-1124 Principles Residues are extracted from high moisture products (>75% water) with methanol, found to be the most effective extractant for N-methylcarbamates in tests using radiolabeled materials. The filtered extract is concentrated with a system that permits evaporation of the relatively high boiling point methanol without destroying heatlabile residues. Apparatus Buchner funnel (Buchner), porcelain, 12 cm diameter evaporator, vacuum rotary with circulating chilled liquid (see Figure 401-b). Maintain 1+1 water/ethylene glycol solution in condensing coils and around receiving flask at –15° C with 1/2 horsepower cooling unit. Insulate condenser with Styrofoam or other material. Control evaporator vacuum with vacuum pump and gauge; manometer may be used but is not preferred. filter paper, Sharkskin, or 597 S&S, to fit Buchner flask, round-bottom (r-b), 2 L, Ts 24/40 homogenizer, Polytron Model PT 10-35, with PT 35K generator containing knives, head equipped with metal (not Teflon) bushing homogenizer jar, four-side, glass, 1 qt magnetic stirrer, star, 10 mm diameter × 8 mm height vacuum filtration flask, 500 mL Reagents methanol, distilled from all-glass apparatus Directions • Add 150 g chopped high moisture product and 300 mL methanol to homogenizer jar. • Homogenize mixture 30 sec at about half speed (setting of 7) and then 60 sec at full speed. • Vacuum filter homogenate through Buchner fitted with filter paper and collect filtrate in 500 mL vacuum filtration flask. Reduce vacuum during filtration if filtrate begins to boil. • Transfer portion of filtrate equivalent to 100 g sample to 2 L r-b flask. Figure 401-b Vacuum Rotary Evaporator To remove higher boiling solvents from solutions containing heat-labile residues. Water/ethylene glycol at –15° C cools receiving flask of rotary evaporator and (insulated) evaporator condenser. Condenser (insulated) Motor Cooling unit Water bath 35° C Constant temperature bath circulator -15° C Needle valve Pump Manometer To vacuum pump

SECTION 401 Pesticide Analytical Manual Vol I Odium sulfate, anhydrous, granular, reagent grade; see Section 204 for han- dling directions toluene, distilled from all-glass apparatus eluant: 25%(v/v)toluene/acetonitrile Preparation of Silanized Celite 545 Slurry 150 g Celite 545 with IL (1+I)hydrochloric acid/ water in 2L beaker, over with watch glass, and stir magnetically while boiling 10 min Cool slurry, filter, and wash with distilled or HPLC grade water until filtrate is neutral Wash Celite with 500 mL methanol followed by 500 mL methylene chloride and then air dry celite in hood on watch glass to remove solvent Transfer Celite to I L glass-stoppered (g-s) Erlenmeyer flask. Heat unstop- pered flask in 120 C oven overnight and then cool flask in desiccator Place flask in hood and carefully pipet 3 mL dichlorodimethylsilane onto Celite. Stopper flask, mix well, and let flask remain at room temperature 4 Add 500 mL methanol to flask. mix. and let stand 15 min. d Celite and wash with isopropanol until neutral Air dry silanized Celite in hood to remove isopropanol Dry silanized Celite in 105C oven 2 hr and cool in desiccator. Store sila nized Celite in g-s container. Test Celite for total silanization with two tests Place about i g celite in 50 mL water; silanized Celite will float Place second 1 g Celite in 20 mL toluene saturated with methyl red; silanized Celite will appear yellow. If particles of Celite are dispersed in water and/or appear pink with methyl red/ toluene solution, active sites still exist on Celite; repeat silanization Purification of charcoal s y urry 100 g Nuchar S-N with 700 mL hydrochloric acid, cover with watch glass, and stir magnetically while boiling 1 h Add 700 mL water. stir. and boil additional 30 min Cool slurry, filter, and wash with water until neutral Wash Nuchar S-N with 500 mL methanol followed by 500 mL methylene chloride, and air dry Nuchar S-N in hood to remove solvent. Dry Nuchar S-N in 120C oven 4 hr. Cool in desiccator. Store NucharS-N in g-s container. Testing of Charcoal/ Celite Prepare cleanup column of (1+4)(w/w) charcoal/Celite as described be- Prepare methanol solution of 5 ug/mL each carbaryl, methiocarb, methio- carb sulfoxide, and methomyl Use freshly prepared mixed standard solu- 401-6 Form FDA 2905a (6/92]

SECTION 401 401–6 Transmittal No. 94-1 (1/94) Form FDA 2905a (6/92) Pesticide Analytical Manual Vol. I sodium sulfate, anhydrous, granular, reagent grade; see Section 204 for handling directions toluene, distilled from all-glass apparatus eluant: 25% (v/v) toluene/acetonitrile Preparation of Silanized Celite 545 • Slurry 150 g Celite 545 with 1 L (1+1) hydrochloric acid/water in 2 L beaker, cover with watch glass, and stir magnetically while boiling 10 min. • Cool slurry, filter, and wash with distilled or HPLC grade water until filtrate is neutral. • Wash Celite with 500 mL methanol followed by 500 mL methylene chloride, and then air dry Celite in hood on watch glass to remove solvent. • Transfer Celite to 1 L glass-stoppered (g-s) Erlenmeyer flask. Heat unstoppered flask in 120° C oven overnight and then cool flask in desiccator. • Place flask in hood and carefully pipet 3 mL dichlorodimethylsilane onto Celite. Stopper flask, mix well, and let flask remain at room temperature 4 hr. • Add 500 mL methanol to flask, mix, and let stand 15 min. • Filter silanized Celite and wash with isopropanol until neutral. • Air dry silanized Celite in hood to remove isopropanol. • Dry silanized Celite in 105° C oven 2 hr and cool in desiccator. Store silanized Celite in g-s container. • Test Celite for total silanization with two tests. Place about 1 g Celite in 50 mL water; silanized Celite will float. Place second 1 g Celite in 20 mL toluene saturated with methyl red; silanized Celite will appear yellow. If particles of Celite are dispersed in water and/or appear pink with methyl red/toluene solution, active sites still exist on Celite; repeat silanization. Purification of Charcoal • Slurry 100 g Nuchar S-N with 700 mL hydrochloric acid, cover with watch glass, and stir magnetically while boiling 1 hr. • Add 700 mL water, stir, and boil additional 30 min. • Cool slurry, filter, and wash with water until neutral. • Wash Nuchar S-N with 500 mL methanol followed by 500 mL methylene chloride, and air dry Nuchar S-N in hood to remove solvent. • Dry Nuchar S-N in 120° C oven 4 hr. Cool in desiccator. Store Nuchar S-N in g-s container. Testing of Charcoal/Celite • Prepare cleanup column of (1+4) (w/w) charcoal/Celite as described below. • Prepare methanol solution of 5 µg/mL each carbaryl, methiocarb, methiocarb sulfoxide, and methomyl. Use freshly prepared mixed standard solution; methiocarb sulfoxide degrades in solution