Shape-selective separation of polycyclic aromatic hydrocarbons on protoporphyrin-silica phases. Effect of surface porphyrin distribution on column efficiency.
The chromatographic performance of various metalloprotoporphyrin-silica (MProP-silica) packing materials prepared using different porphyrin immobilization schemes is examined. Column efficiency and solute resolution for the shape-selective separation of polycyclic aromatic hydrocarbons (PAHs) can be improved significantly by preparing phases with lower porphyrin coverages and with a more homogeneous distribution of the porphyrin species on the surface. The latter is accomplished by spreading/diluting the number of aminopropyl reactive sites on the silica surface via mixing an inert methyltrimethoxysilane with 3-aminopropyltriethoxysilane during this preliminary reaction step. Subsequent covalent attachment of the ProP via amide bonds to the pendant amine sites results in a more even distribution of the porphyrins on the surface. Band shapes and retention times as a function of injected solute concentration as well as HPLC separation of various test mixtures of PAHs (including standard reference material SRM 869) are used to confirm the enhanced performance of these so-called "spread" phases. Changes in the nature of the immobilized porphyrin distribution on the silica surface are further probed by a coupled redox/UV-Vis absorbance method, and results suggest a decrease in the number of ProP species immobilized as aggregates on the surface.
Chen
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Department of Chemistry, The University of Michigan, Ann Arbor 48109-1055, USA.
Ruedel
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Meyerhoff
M E
ME
D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D010084:Oxidation-Reduction; D011084:Polycyclic Aromatic Hydrocarbons / Q000737:chemistry* / Q000302:isolation & purification*; D011166:Porphyrins / Q000737:chemistry*; D012822:Silicon Dioxide; D013053:Spectrophotometry
D011084:Polycyclic Aromatic Hydrocarbons; D011166:Porphyrins; D012822:Silicon Dioxide