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The creation of tetracycline (TC) responsive molecularly imprinted xerogels (MIXs) was investigated using electronic absorbance, liquid chromatography-ion-trap mass spectrometry (LC-ITMS), and first-principles theory. Experimental results show that the template molecule converts to its epimer, 4-epitetracycline (ETC), during the imprinting process. Additionally, end capping of the MIX surface silanols transforms TC into anhydrotetracycline (ATC) and 4-epianhydrotetracycline (EATC). Hence, despite aiming to imprint for a single analyte (TC), one simultaneously imprints for up to four analogs (TC, ETC, EATC and ATC) within a MIX. Binding studies using LC-MS showed the binding of the prepared xerogels with the four analogs. In some formulations, preferential uptake of ETC, EATC and ATC relative to the template molecule (TC) was observed. Computations of the interaction energies between silane monomers and the four analogs reveal that ETC, EATC and ATC have higher interaction energies and are more likely to be imprinted in comparison to TC.

A series of silica-based tetracycline (TC)-imprinted xerogel sorbents were prepared by sol-gel processing and were characterized for TC binding. Molecularly imprinted xerogels (MIXs) formed from allyltriethoxysilane (AtEOS) and tetraethoxysilane (TEOS) and end capped with trimethylchlorosilane exhibited the best analytical performance (imprinting factor, IF, of 7.46±0.13). Computational modeling was used to estimate the interaction energy (IE) between TC and each type of silane to evaluate our ability to predict the analytical performance of a given MIX. Rankings from the computations agreed with the experimental data showing the AtEOS having the highest IE in comparison to the other formulations. Together, these results demonstrate the potential and limitations of using theoretical calculations to guide the development of analyte selective MIXs in comparison to arbitrary trial and error approaches traditionally used to produce MIXs as sorbents for solid phase extraction., (Copyright © 2010 Elsevier B.V. All rights reserved.)