MIT-SPR Technology For The Detection Of Salicylic Acid In The Liquid Phase And The Research Of SO₂in The Gas Phase

Molecular imprinting technology (MIT) developed rapidly since the eighties of thetwentieth century as a new chemical separation and analysis technology. It has been appliedin many fields such as chromatographic separation, solid phase extraction, organicsynthesis and biological sensors, because of its predetermination, specific recognition andextensive practicability. Surface plasmon resonance (SPR) as an optical monitoringtechnology is widely used in the analysis of the interaction between molecules, because ofits characteristics of small dosage, label free and high sensitivity. Molecularly imprintedpolymers (MIPs) as the sensitive element of the surface plasmon resonance sensor are usedfor molecular detection, which combines the advantages of both technologies.This paper firstly established a method for the detection of salicylic acid. A reactionsolution is prepared in acetonitrile solvent with salicylic acid as the template molecule,methyl acrylic acid as monomer, the crosslinking agent is ethylene glycol methacrylate andbenzophenone as initiation. Under the irradiation of UV light source the molecularimprinting film (MIF) of salicylic acid was formed on the gold surface. Then use theacetonitrile acetic acid eluate（V:V=9:1） to eluat the MIF, the drop of coupling angle was0.3°in50min, indicates that the MIF was prepared successfully. After removal of thetemplate molecule-salicylic acid, the first step was to inspect its response to10-7mol/Lsalicylic acid using SPR, from the adsorption kinetics we can see that the MIF showed aresponse to salicylic acid; then we tested the adsorption to different concentrations ofsalicylic acid, the results showed that there were good linear relationship between thecoupling angle shifts and the concentrations from the range of10-11to10-6mol/L. Finally,the selectivity of the imprinted films was investigated, the10-6mol/L salicylic acid,p-salicylic acid, vanillin solutions were pumped in respectively. The coupling angle shiftswas:0.3257°,0.0608°and0.0945°. Even though they have the similar molecular structure,the coupling angle shift for the binding of salicylic acid was still more than3-fold higherthan the affinity binding of the other two moleculars. A control experiment was performedby non-molecular imprinting film to10-6mol/L salicylic acid. It showed the coupling angleshift is only0.0352°, which is about9-fold lower than the shift measured with MIF, so MIFhas good recognition ability for salicylic acid.The second part of this paper applies the MIT and SPR technology to detect the gas. Sulfur dioxide (SO2) as the template molecule, acrylamide as the functional monomer,ethylene glycol methacrylate as crosslinking agent, benzophenone as initiator, and alcoholas porogen, the reaction solution was prepared. We adopted the same polymerizationprocess as the liquid phase. After SO2molecularly imprinted film was prepared, theadsorption behavior of the polymer to SO2was detected. Finally, we got the conclusion thatthe combination of the two technologies can be used for the detectiong of SO2gas, whichprovided a new method for the detection of SO2.