Analytical Sciences

Selective Solid-Phase Extraction of α-Tocopherol by Functionalized Ionic Liquid-modified Mesoporous SBA-15 Adsorbent

Min LI, Patrisha J. PHAM, Charles U. PITTMAN Jr, and Tingyu LI

Department of Chemistry, Mississippi State University, Box 9573, Mississippi State, MS 39762, USA

Ordered mesoporous adsorbents were prepared by physically grafting functionalized ionic liquids onto SBA-15 (a mesoporous siliceous substrate) using incipient wetness immersion method. These adsorbents were successfully applied to the selective extraction and separation of α-tocopherol (an isomer of vitamin E) from a model mixture of soybean oil deodorizer distillate. Various parameters affecting adsorption process such as adsorption time, the structures and loadings of ionic liquids, the adsorption isotherm, and the reusability of adsorbent were investigated using liquid-solid extraction. As high as 211 mg/g adsorbent of the adsorption capacity for α-tocopherol was obtained through the adsorption isotherm tests using [emim][Gly]/SBA-15 (functionalized ionic liquid 1-ethyl-3-methylimidazolium glycine which was physically coated on SBA-15) as the adsorbent, in which the functionalized ionic liquids contained the amino acid glycine as the anion. The adsorbent [emim][Gly]/SBA-15 also exhibited a very high adsorption selectivity for α-tocopherol. The extraction selectivity or the ratio of distribution coefficients between α-tocopherol and the major interference component glyceryl triundecanoate (K_{d(α-tocopherol)}/K_{d(triglyceride)}) was 10.5. The concentration of α-tocopherol was significantly increased from 15.6% in original feedstock solution that contained fatty acid methyl ester, triglyceride and a-tocopherol to 73.0% after stripping by diethyl ether. Five adsorbent recycle tests showed good reusability of the functionalized ionic liquidmodified mesoporous adsorbent.

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