164 



GEHRS 



SAMPLE 



ORGANIC 



ETHER (OR IVIeClj) 

 1/V NaOH 



AQUEOUS 



FLORISIL 

 COLUMN 



HEXANE 



AQUEOUS 



ORGANIC 



HEXANE/BENZENE 

 (8/1) 



BENZENE/ETHER 

 (4/1) 



METHANOL 



Fig. 3 Separation and fractionation process used to obtain materials 

 for environmental testing. (Data from Rubin et al., 1976.) 



aquatic organisms, found an inverse association between toxicity and 

 boiling point. Legore (1974) concurred with this relationship and 

 suggested that solubility was the primary factor. 



More recent investigations (Gehrs, 1975; Parkhurst, Gehrs, and 

 Rubin, 1978) have begun to separate complex mixtures on the basis 

 of chemical similarities of compounds (Fig. 3). Rubin et al. (1976) 

 adapted this chemical fractionation approach, which was developed 

 for evaluating tobacco smoke, to aqueous samples. The scheme 

 makes use of the differential solubility of various compounds to 

 produce from three to more than 20 semidiscrete and reproducible 

 fractions. Mutagenesis testing (Epler et al., 1978) has been used to 

 identify the more active of these fractions, with subsequent 

 subfractionation and testing allowing eventual determination of 

 problematic compounds. 



Parkhurst, Gehrs, and Rubin (1978) used a similar- approach with 

 Daphnia magna as the test species. They found (Table 1) that the 

 neutral fraction, which comprised only 7% of the soluble materials in 



