Two SiO2 samples were prepd. by conversion of (EtO)(4)Si, modified with a com. nonionic surfactant and optionally with 1,3,5-Me3C6H3 and NH4F precursors, and functionalized with H2N(CH2)(3)Si(OEt)(3) added at molar ratio 1:6 to the SiO2. Adsorption of chlorogenic acid from its Me2CHOH solns. (concn. 350-7000 mg/L) was studied at 25 degrees C by shaking a suspension of modified silica sample in the chlorogenic acid soln. for 24 h and then spectrophotometric assaying the concn. of chlorogenic acid remaining in the liq. phase after removal of the adsorbent. Both adsorbents had similar waveforms of isotherms and the max. of adsorption capacity at 250 or 244 mg/g. Moreover, the morphol. of SiO2 samples was studied by scanning electron microscopy.