Solid-phase extraction based on modified mesoporous microspheres for the determination of repaglinide in plasma by HPLC

Mesoporous silica particles (MSPs), such as MCM-41 (Mobil Catalytic Material Number 41), and SBA-15 (Santa Barbara Amorphous-15), are solid materials, which are comprised of a honeycomb-like porous structure with hundreds of empty channels (mesopores) that are able to absorb/encapsulate relatively large amounts of bioactive molecules. Their unique properties, such as high surface area, large pore volume, tunable pore size with a narrow distribution, and good chemical and thermal stability of these materials, make them potentially suitable for various applications in many fields of technology such as chemical and pharmaceutical sciences. In general, the surface area of a porous material is higher than the surface of an analogous non-porous material. Thereby the internal surface area is usually much higher than the one contributed by the external surface. The ease of introducing various organic functional groups, either through covalent bonding or electrostatic interactions, provides high level of versatility and many mechanized features to the mesoporous silica materials. Due to the high pore volume and surface area of MSPs they are especially suitable carrier for the loading of hydrophobic drugs. The present study was to develop MSPs as carrier to load with repaglinide as a poorly water soluble drug. For this propose, SBA-15 was prepared with templating approach. After synthesis of the MSP, the impact of the surface functionalization of SBA-15 with methyl group was investigated on drug loading efficiency of repaglinide. To investigate the enrichment efficiency of the microspheres,extraction conditions were optimized in the following work. To acquire the maximum extraction efficiency of the target analyt the amounts of MSN microspheres required were optimized first. For the sake of enhancing extraction efficiency, the selection of extraction time is important after the sorbents are dispersed in to solution. In our study,different extraction time were investigated. The selection of an appropriate elution solvent is quite important in a SPE procedure. In this study some solvents were examined for improving the extraction efficiency of repaglinide. The volume of elution solvent and elution time are also important factors to obtain reliable and reproducible analytical results that were investigated. In optimom condition our loading studies indicated that there was 28 and 75% loading efficiency in the presence of SBA-15 and SBA-CH3 as carrier. Therefore, the findings clearly showed the substitution of silanol groups with phethyl groups had a positive effect on the loading efficiency (LE). This improvement in LE may be attributed to the hydrophobic interaction between the lipophilic drug repaglinide and the hydrophobic channels of SBA-15.