Study On The Preparation And Application Of Poly(N-isopropylacrylamide) Monolithic Columns

Biological samples are very complex, because they contain many endogenous substances,while the concentration of the analytes in the biological samples is often very low and thesample volume is also less. Therefore, sample pretreatment techniques will become the mostcomplex, cumbersome and key step in the entire chromatographic separation and analysisprocess. In such case, developing a simple, rapid, sensitivity and selectivity samplepretreatment technique will become an important part to improve the analysis quality ofbiological samples. Solid phase extraction (SPE) has gained popularity as a useful techniquefor trace drug enrichment of biological samples and simultaneous removal of interferingmatrix. Moreover, sorbent for core of the solid-phase extraction has become a critical factor.In recent years, organic polymer monolith that due to have some advantages such as easypreparation, larger surface area, high permeability and high selectivity, also become verypopular sorbent for SPE.In this paper, a new poly(N-isopropylacrylamide-co-ethylene dimethacrylate)[poly(NIPAAm-co-EDMA)] monolithic column was prepared by in situ free-radical polymerization. The morphology of monolithic column was investigated by scanning electron microscope, effect of flow rate of mobile phase on pressure drop across the columns was also characterized. Then, the new monolithic column was operated as SPE columnwith column switching technology coupled to a HPLC-UV system for simultaneous determination of three dipine series in human and urine. The results showed that the established method was an effective method for trace drug enrichment in biological samples analysis.In addition, a new polymer monolithic column using NIPAAm and methacrylic acid(MAA) as the monomers, and EDMA as the crosslinker was synthesized via in situfree-radical polymerization. The new monolithic column was evaluated with nifedipine andnitrendipine. The effects of the mobile phase composition, flow rate, and temperature onseparation efficiency were investigated. The results indicated that the new monolithic columncan improve peak shape and chromatographic resolution by changing above conditions.