grab samples

D. Esterification and Clean-up
(5) Combine the I ml concentrate with 0.5 ml of boron trifluoride 3 -methanol esterification reagent.
Heat in water bath for 30 min at 50°C; cool.
(6) Add 5 ml of 5% aqueous sodium sulphate solution and extract with two ml portions of hexane.
Concentrate hexane extract to I ml with stream of dry nitrogen.
(7) Pass hexane extract through mini-purification column of 2.0 cm of neutral anhydrous sodium
sulphate over 2.0 cm of high-grade Florisil in disposable pipette. Elute with 10 ml of benzene.
(8) Concentrate to 0.5 ml in stream of dry nitrogen. Make up to I ml with benzene.
(9) Analyze by injection of 10 JLI quantities in at least two different chromatographic columns.
Identify components.
Note: Methylation step is very critical. Keep tubes tightly capped at all times.
References
ANON. 1974. Analytica l methods manual. Inland Waters Dir .. Water Qual. Br. Thorn Press Ltd .. Ollawa. Onl.
CHAU. A. S. Y. 1972. Analysis of chlorinated hydrocarbon pesticides in waters and wastewaters. Inland Waters Dir .. Water Qua l. Br..
Ottawa. Ont. 56 p.
Group 3 (Chlorinated Phenols)
A. Summary of Methods
The chlorophenols are extracted from acidified water-sediment slurry with benzene. Acidic
compounds such as halogenated phenols and substituted phenoxyacetic acids are extracted from benzene
extract by means of 0.1 M potassium carbonate solution.
The chlorophenols within the carbonate solution are then acetylated by addition of acetic anhydride,
and the chlorophenol acetates are extracted with hexane (Anon. 1974; Chau 1972). This extract contains
only acidic alcohols.
B. Reagents
All reagents should be" pesticide resid ue grade." Redistilla tion of solvents shou Id im prove purity.
Acetone
Benzene
Petroleum ether
Acetic anhydride (redistill three times)
0.1 M potassium carbonate (twice extracted with benzene)
Three gas chromatographic columns are suggested:
(a) 6 ft X I/." 11% OV-17 /QF-I on Chromosorb Q (80-100 mesh);
(b)6ft x W'4%OV-101 + 6%OV-210ChromosorbW(80-100mesh);
(c) 6 ft X W' 3% OV -225 on high performance Chromosorb Q (80- 1 00 mesh).
Isothermal oven 200°C.
C. Analysis/Extraction
(I) Make up slurry of20- 40 g sediment with deionized-distilled water (use = 10% by wt.).
(2) Combine 30 ml of benzene with water-sediment slurry. Extract three times, using 30 ml benzene
each time.
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