A nonaqueous anion-exchange solid-phase extraction technique has been developed for analyzing particulate extracts of ambient air samples and combustion source samples. The technique has been used for sample preparation and sample prefractionation in bioassay-directed fractionations. This technique employs an anion-exchange resin to separate complex particulate extracts into four discrete fractions, which are characterized as neutral/basic, polar neutral/weak acid, weak acid, and stronger acid components. Two ambient air particulate extracts from Boise, Idaho, were analyzed by the developed method. Qualitative chemical analysis of the resulting fractions by gas chromatography-mass spectrometry showed agreement with the chemical class fractionation predicted by the separation of standard reference compounds. (Copyright (c) 1993 Gordon and Breach Science Publishers S.A.)