title: Preparation of nanomagnetic absorbent for partition coefficient measurement.
abstract: In this paper, we report a new method based on supercritical carbon dioxide (scCO(2)) to fill and distribute the porous magnetic nanoparticles with n-octanol in a homogeneous manner. The high solubility of n-octanol in scCO(2) and high diffusivity and permeability of the fluid allow efficient delivery of n-octanol into the porous magnetic nanoparticles. Thus, the n-octanol-loaded magnetic nanoparticles can be readily dispersed into aqueous buffer (pH 7.40) to form a homogenous suspension consisting of nano-sized n-octanol droplets. We refer this suspension as the n-octanol stock solution. The n-octanol stock solution is then mixed with bulk aqueous phase (pH 7.40) containing an organic compound prior to magnetic separation. The small-size of the particles and the efficient mixing enable a rapid establishment of the partition equilibrium of the organic compound between the solid supported n-octanol nano-droplets and the bulk aqueous phase. UV-vis spectrophotometry is then applied to determine the concentration of the organic compound in the aqueous phase both before and after partitioning (after magnetic separation). As a result, logD values of organic compounds of pharmaceutical interest determined by this modified method are found to be in excellent agreement with the literature data.
authors.affiliation: The Surface and Catalysis Research Centre, School of Chemistry, University of Reading, Whiteknights, Reading RG6 6AD, UK. s.c.e.tsang@reading.ac.uk
authors.forename: Shik Chi
authors.initials: SC
authors.lastname: Tsang
authors.forename: Chih Hao
authors.initials: CH
authors.lastname: Yu
authors.forename: Xin
authors.initials: X
authors.lastname: Gao
authors.forename: Kin Y
authors.initials: KY
authors.lastname: Tam
mesh_terms: D020003:1-Octanol / Q000737:chemistry*; D002245:Carbon Dioxide / Q000737:chemistry; D005290:Ferric Compounds / Q000737:chemistry*; D008280:Magnetics; D053758:Nanoparticles / Q000737:chemistry*; D016062:Porosity; D012822:Silicon Dioxide / Q000737:chemistry*; D013818:Thermogravimetry; D014867:Water / Q000737:chemistry
chemical_list: D005290:Ferric Compounds; D014867:Water; D002245:Carbon Dioxide; C000499:ferric oxide; D012822:Silicon Dioxide; D020003:1-Octanol