sampling and 

 analytical procedures 



MONITORING water for specific pollutants 

 requires acceptable sampling and analyti- 

 cal procedures and the following references con- 

 tain such guides and procedures. This doesn't pre- 

 clude the use of other reliable methods {21, 123, 

 137,159,175,181). 



The methodology for pesticides is currently 

 somewhat dispersed. For purposes of clarity and 

 as an aid to laboratories, the following recom- 

 mended instructions for extraction and analysis 

 are set forth. 



Methods for Analyses of Chlorinated and 

 Phosphate Pesticides in Water 



For extraction and preparation of the samples 

 for multple detection (electron capture or therm- 

 ionic gas-liquid chromatography and confirma- 

 tion by thin-layer chromatography), follow the 

 methods of Burchfield, et al. as outlined in Analysis 

 of Pesticide Residues {174). 



General Discussion of extraction of pesticides 

 from water. Generally, in batch-method extrac- 

 tion, chloroform is the solvent of choice, with the 

 following modifications. After extraction, pass the 

 combined chloroform extracts through a column 

 of anhydrous sodium sulfate, collecting the eluate 

 in a 500 ml Kuderna-Danish evaporator fitted with 

 a calibrated collection tube. When all of the extract 

 has passed through, rinse the column with three 

 5 ml portions of hexane. Add a 20-mesh carborun- 

 dum boiling chip and place a Snyder column on 

 the Kuderna-Danish evaporator and concentrate 

 to about 5 ml. Add 25 ml hexane to evaporator 

 and concentrate to about 5 ml. Repeat addition of 

 hexane and concentrate two more times to elimi- 

 nate most of the chloroform. After last evapora- 

 tion, dilute to 10 ml with hexane for determination 

 by electron-capture gas chromatography and con- 

 firmation by thin-layer chromatography. 



Continuous methods are used only when it is 

 necessary to extract large volumes of water and are 

 adapted more to research purposes than to routine 

 analysis. 



In determinations, no cleanup is necessary if 

 potable water is being analyzed and the analyst can 

 go directly to electron-capture or thermionic gas 

 chromatography with thin-layer chromatography 

 for confirmation if necessary. Operating parame- 

 ters, retention times, and supporting data are found 

 in the FDA pesticide analytical manual {173). 

 The complete methods are given A.O.A.C. 79th 

 annual meeting {33) and changes in these methods 



178 



