An apparatus for changing relative concentrations of first and second analyte substances in an analyte sample comprises a sample cell defining a sample chamber therewithin, and a semipermeable boundary member disposed in the sample chamber to define first and second sides of the sample chamber. This invention allows the consumer to more thoroughly engage with the subject matter of the primary advertisement, with the effect of supplementing and enhancing the advertising message of the primary advertisement. The second active hydrogen-containing compound comprises an active hydrogen-containing phosphite compound. The comment stream and the content stream are stored separately.