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 cleanupTransmittal 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 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￾centrations of 1 µg/mL. Store solutions in actinic glassware, and keep in refrigera￾tor 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