An extreme vertices mixture design approach to the optimisation of 1,2,3-trichlorobenzene specific molecularly imprinted polymers

Abstract

Traditional approaches to molecularly imprinted polymer (MIP) design and optimisation typically afford a template (T) : functional monomer (FM) : crosslinker (CL) ratio of 1 : 2 : 20 to 1 : 4 : 20. This approach for 1,2,3-trichlorobenzene (7) as template gave a styrene based MIP (MIP_STY) with an imprinting factor (IF) = 1.3. An extreme vertices mixture design (EVMD) approach was applied, and in two design cycles, 15 total experimental points, the optimum composition for MIP_STY was determined as 0.40 : 0.05 : 0.55 (T : FM : CL) with IF = 2.8. Refinements gave optimum T : FM : CL ratios for the functional monomers: 4-vinylpyridine (4VP, 0.40 : 0.02 : 0.58); 2,4,6-trimethylstyrene (TMS, 0.40 : 0.02 : 0.58) and 2,3,4,5,6-pentafluorostyrene (PFS, 0.30 : 0.12 : 0.58) with IF = 2.8, 2.8 and 3.7 respectively. These ratios deviated significantly from the traditional MIP synthesis ratio. The low levels of FM for all MIPs, except for MIP_PFS, suggest that imprinting was more consistent with T–CL, than FM–T, interactions. Analysis of the specific interactions and removal (SR) of 7 with these MIPs revealed that the SR with MIP_STY increased from 36% at 0.02 STY to 48% at 0.13 STY; with MIP_TMS SR increased from 38% at 0.02 TMS to 42% at 0.10 TMS; and with MIP_PFS SR increased from 34% at 0.02 PFS to 56% at 0.14 PFS. MIP_4VP saw a decline in SR with increasing FM, with the highest SR was 35% at 0.02 4VP. This is consistent with changes in the non-specific interactions between 7 and the MIPs. Increasing the proportion of PFS produced the largest increase in imprinting of 7 demonstrated by the highest SR (56%) and highest IF (3.7). The application of an EVMD approach resulted in the IF of MIP_STY increased from 1.3 to 2.8. The highest IF achieved by this study was 3.7 for MIP_PFS in proportions of 0.30 : 0.12 : 0.48 (T : FM : CL).