The present invention provides a composition for absorbing a gaseous unsaturated compound comprising a tetrazine compound incorporated in a polymeric substrate, wherein the tetrazine compound is stable to the presence of moisture. The invention further provides a method of retarding the ripening or senescence of fruit or other plant material using the composition of the present invention. Also provided are methods of removing a gaseous unsaturated compound from an environment and methods of measuring the concentration of, or indicating the presence of, a gaseous unsaturated compound.