b A continuous, multichamber liquidliquid extractor, with interncl solvent recycle, for the extraction of nonpolar contaminants from natural waters is described. The multichamber arrangement makes it possible to judge the completeness of extraction of a given component from the aqueous stream. Recoveries as high as 100% are obtained by applying the apparatus to the extraction of the pesticides aldrin, dieldrin, and endrin and their manufacturing intermediates. ARTS per billion concentrations of P chlorinated hydrocarbon pesticides in natural waters have been reported( 1 ) to cause the destruction of fish. The need for determining trace amounts of these pesticides in ground water and surface water is, therefore, evident.Two methods which have been utilized extensively for the estraction of pesticides from water are adsorption on activated carbon with subsequent desorption by organic solvents (3) and liquid-liquid estraction (4). The former method was studied by Rosen and Middleton (S), who obtained low recoveries of benzene hesachloride; chlordan; 1,l)ltrichloro-2,2-bis(p-chlorophenyl) ethane (DDT); 1,2,3,4,10,10-hexachloro-l~4,4a,(TDE, DDD) ; and 1,2,3,4,10,10-hexachloro-6,7-epoxy-l,4,4~,5,6,7,8,8a -octahydro -l ,4 -endo -endo -5,s-dimethanonaphthalene (endrin) by carbon adsorption and subsequent desorption with chloroform.Teasley and Cos (4), utilizing liquidliquid ext,raction, extracted 1-liter water samples batchwise and determined chlorinated hydrocarbons by microcoulometric gas chromatography. The quantities estracted were too small, however, for infrared analysis. Of the two procedures, the liquid-liquid estraction method was preferred by the authors, as previous esperience indicated that some of the pesticides and their intermediates are not stable on activated carbon. I t is possible that this effect contributed to the low results obtained by Rosen and Middleton ( 3 ) .Only one laboratory apparatus with internal recovery and recycle for the continuous liquid-liquid estraction of organic compounds from aater ia reported in the literature ( 5 ) : a singlechamber unit, developed for the eatraction of trace organics from sea water.The present paper describes a multichamber apparatus, each chamber of which is capable of efficiently extracting low concentrations of nonpolar organic compounds from water. The efficiency of extraction of each chamber and, therefore, the completeness of estraction are readily judged from the concentration of a particular component in successive chambers of the apparatus. This feature is especially useful in the estraction of the newer pesticides, for which the distribution coefficient between water and the respective organic solvents is not known.The present apparatus was tested by extracting several chlorinated hydrocarbon pesticides and their manufacturing intermediates from water. As the apparatus may be used for the extraction of extremely large water samples, it is possible to isolate, purify, Figure 1 . Detailed drawing of extraction chamber and identify very minute concentra...
