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(3) Extract benzene extracts from (2) three times using 30 ml of 0.1 M potassium carbonate each time. (4) Combine carbonate extracts and add I ml of thrice distilled acetic anhydride. Add J 0 ml of hexane. (5) Stir vigorously for I h. (6) Remove hexane extract and analyze by gas chromatography; preconcentration may be necessary in rotary evaporator (40 - 50°C water bath). Note: Multi-column analysis and mass spectrometric investigation of products are necessary for product iden ti fica tion. References ANON. 1974. Analytical methods manua l. Inla nd Waters Dir., Water Qual. Br. Tho rn Press Ltd., Ottawa, Ont. 56 p. CHAU, A. S. Y. 1972. Analysis of chlorinated hydrocarbon pesticides in water a nd w astewaters. Inland Waters Dir., W a te r Qua l. Br., Ottawa, Ont. 56 p. 6.20 N-methylcarbamate Pesticide Residues I. Theory The carbamates are well known insecticides of which SEVIN® has been used the longest. In natural waters these compounds can undergo hydroxylation, as well as degradation. A selection of N-methyl carbamates is given in Table 3. II. Summary of Method After extraction, the carbamates are hydrolyzed in methanolic potassium hydroxide. The resulting hydrolysates are isolated and derivatized with pentaftuorobenzyl bromide (PFB) to produce PFB-ether derivatives. The derivatives are cleaned up and fractionated on a silica gel pre-column and separated by gas chromatography with an electron-capture detector (APHA et al. 1975). III. Interferences Organophosphate pesticides and phthalic acid esters may hydrolyze to phenols or phthalic acid. However, in the method outlined below the phenols do not appear to cause interferences on the chromatographic columns and the phthalate esters are nonvolatile under the specified conditions. IV. Detection Limits The limits of detection are determined by the limitation the reagent blanks impose rather than the sensitivity of the derivatives. The problem of reagent blanks may be reduced by use of fresh solvents and redistillation ofsolvents to improve purity. V. Reagents Pentaftuorobenzyl bromide (PFB) I % (V I V) in acetone. Store in dark container. Prepare every 2 wk. Methanolic potassium hydroxide - 10% (W I W) . Dissolve 109 reagent grade potassium hydroxide in 100 ml pesticide grade methanol in dark bottle. Potassium carbonate solution: (I) (0.1 M) 13.8 g K 2 CO J in I I deionized-distilled water. (2) 5% solution 109 K 2CO J in 200 ml deionized-distilled water. 50% sulphuric acid solution. Extract two to three times with equal volumes of benzene. Silica gel. Deactivate by adding deionized-distilled water, 1.5% (W IW). Store in tightly capped container. Coburn et aJ. ( 1976) specify grade 950 silica gel from Davison Chemical, Bal timore, Md. 2 1226. 61
Anhydrous sodium sulphate. Two gas chromatographic columns are required: (a) 3.6% (W /W) OV-IO I + 5% (W /W) OV-210 on SO-100-mesh Chromosorb W, acid washed, DMCS-treated; (b) 3%(W /W) OV-225 on SO - IOO-mesh Chromosorb W (HP). TABLE 3. Some N-methylcarbamates and related compounds. Trade name Sevin® Mesurol® Baygon® Landrin® Mobam® Carbofuran® Temik® Promecarb® Banol® Carzol® Methomyl® Elocron® Dimetan® Butacarb® *Following Chemical Abstracts. Systematic chemical name* 1-N a pthalenyl-N-methylcarbamate 3,5 Dimethyl-4-(methylthio )-phenyl N-methylcarbama te 2-( 1- Methylethoxy)-phenyl-N-methylcarbama te 2,3,5-Trimethylphenyl-N-methy Icarbama te 3-(I-Ethylpropyl) phenyl-N-methylcarbamate and 3-(I-Methylbutyl) phenyl-N-methylcarbamate Benzo[b ]thiophene-4-y 1-N-methylcarbamate 2,3-Dihydro-2,2-dimethyl-7-benzofuranyl-Nmethylcarbamate 2-Methyl-2-(methylthio) propanal-O «methylamino) carbonyl) oxime 3-Methyl-5-( I-methylethy 1)-N-methylcarbama te 2-Chloro-4,5 dimethylphenyl-N-methylcarbamate N,N-Dimethyl-N'-(3-«(methylamino-) carbonyl) oxy) phenyl)-methanimidamide monohydrochloride N-«(Methylamino)carbonyl) O-oxy)ethanimidothioic acid-N-methylester 2-( 1 ,3-Dioxolan-2-yl)-phenyl-N- methylcarbamate 5,5-Dimethyl-3-oxo-I-cyclohexen-I-yl-Ndimethylcarbamate 3,5-Bis (I, I-dimethylethyl)phenyl-N-methylcarbamate 62 Trade source Union Carbide Chemagro Corp. Chemagro Corp. Shell Chemical Co. Chevron Chemical Co. Mobil Chemical Niagara Chemical Co. Union Carbide Schering Upjohn Co. NOR-AM Agriculture Products DuPont CIBA-Geigy Chemical Corp. ClBA-Geigy Chemical Corp. Niagara Chemical Co.
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SHELVED WITH SERIAtS no. 1
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· Available from : Scientific Info
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FOREWORD On December 13, 1975, the
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ABSTRACT WALTON, A. (ed. ).1978. Me
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5. Organosilicon compounds 6. Cyani
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The consolidated core sample in the
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drive the core barrel through sand
Page 22: 2.4 Field Notes; Labels for Sample
Page 26: SECTION 4 SAMPLE STORAGE Stored sed
Page 30 and 31: 5.1.4 Dry Coarse Fraction The coars
Page 34: In order to ensure a constant tempe
Page 38 and 39: SECTION 6 CHEMICAL ANALYSIS This se
Page 40 and 41: IV. Reagents Concentrated high puri
Page 42 and 43: (4) The analysis proced ures are ou
Page 44 and 45: (I) Place 220 ml of solution in a 5
Page 46 and 47: Flameless: 0.000 I mgll (solution)
Page 48 and 49: Chelating reagent: ammonium pyrroli
Page 50: B. Reagents Chelating reagent: ammo
Page 54 and 55: efore use. Then rinse with conc. hy
Page 56: (8) Add 3 g of20- 30 mesh high qual
Page 60 and 61: B. Proced ure (\) To 50-ml portion
Page 62 and 63: (5) Analyze the extract or a suitab
Page 64 and 65: will probably involve the analysis
Page 66 and 67: = O.S ml (40°C water bath, use a s
Page 68 and 69: A 9lA-cm column of 10% OV -Ion SO-I
Page 70 and 71: Note: All organohalogen methods sho
Page 74 and 75: VI. Analysis (Coburn et al. 1976) A
Page 76 and 77: analysis is its inability to analyz
Page 78 and 79: SECTION 7 CHEMICAL TESTS WHICH MAY
Page 80: (5) Analyze" after" water sample as
Page 83 and 84: III. Method (Fuller 1969) Place pla
Page 85: GENERAL REFERENCES AND SOURCE MATER
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