Activated carbon and silica gels surface-modified with 2,4 dinitrophenyl hydrazine (DNPH), are examined in terms of their suitability for sampling aldehydes and ketones in vulcanisation fumes. In the presence of various peripheral conditions the selectivity of the method is simulated and validated. Humidity has no significant influence on redetection of the substances being analyzed by the DNPH method. The study demonstrates that the deriving reaction in itself is preceded by an adsorption on the substrate material and that subsequent quantitative transformation to the hydrazone requires different reaction times depending on the reactivity of the carbonyl components.