Synthesis and Evaluation of Uniformly Sized Synephrine-Imprinted Microparticles Prepared by Precipitation Polymerization

Abstract

Uniformly sized synephrine molecularly imprinted polymer (MIP) microparticles were prepared via precipitation polymerization. The presence of the template, the amount of monomer, crosslinker, and porogenic solvent could affect the size distribution and morphology of the polymers. The pseudo-second-order kinetic model could provide a better correlation for the adsorption than the pseudo-first-order model. The intraparticle diffusion study showed that the sorption involved intraparticle diffusion, but that was not the only rate-controlling step. The equilibrium data better fit the Freundlich model than the Langmuir model. The Scatchard plot of MIPs revealed MIPs had two groups of sites with different affinities. Subsequent recognition selectivity experiments demonstrated preferential structural selectivity for synephrine with respect to other structurally similar compounds (i.e., octopamine and tyramine). Compared with the bulk MIP of SYN, the SYN MIP microparticles in this work had higher adsorption selectivity and capacity due to their smaller particle sizes; moreover, the precipitation polymerization was time-saving due to not using a crash-and-sieve process.

Keywords:

• microparticles
• molecular recognition
• molecularly imprinted polymer
• precipitation polymerization
• synephrine

ACKNOWLEDGEMENTS

Financial support from the National Natural Science Foundation of China (Nos. 21366019, 20806037, and 20876131), Jiangxi Province Young Scientists (Jinggang Star) Cultivation Plan (20112BCB23002), Natural Science Foundation of Jiangxi, China (No. 2007GQH1752), Jiangxi Province Higher School Science and Technology Landing Plan Projects (No. KJLD13012), Open Foundation of Key Laboratory of Poyang Lake Ecology, Bio-Resource Utilization of the Ministry of Education (No. Z04998), and Special Funds for Graduate Student Innovation in Jiangxi Province (Nos. YC2011-S005 and YC2012-S017) are gratefully acknowledged.

Notes

^a All polymers are prepared under a nitrogen atmosphere for 24 h at 60°C.

^a Q_e,exp is the amount of SYN adsorbed on the sorbent at equilibrium determined by the experimental.

^b Q_e,cal is the amount of SYN adsorbed on the sorbent at equilibrium calculated by Eqs. (4) or (6).

*α₁ = K _D1/ K _D2; α₁ = K _D1/ K _D3; β₁ = α_1MIP/α_1NIP; β₂ = α_2MIP/α_2NIP; IF _SYN, IF _OCT and IF _TYR are the imprinting factor of MIP for SYN, OCT and TYR, respectively, when the concentrations of SYN, OCT and TYR are 0.25 mmol L⁻¹.