title: Functionalization/passivation of porous graphitic carbon with di-tert-amylperoxide.
abstract: Porous graphitic carbon (PGC) particles were functionalized/passivated in situ in packed beds at elevated temperature with neat di-tert-amylperoxide (DTAP) in a column oven. The performance of these particles for high performance liquid chromatography (HPLC) was assayed before and after this chemistry with the following analytes: benzene, toluene, ethyl benzene, n-propyl benzene, n-butyl benzene, p-xylene, phenol, 4-methylphenol, phenetole, 3,5-xylenol, and anisole. After the first functionalization/passivation, the retention factors, k, of these compounds decreased by about 5% and the number of theoretical plates (N) increased by ca. 15%. These values of k then remained roughly constant after a second functionalization/passivation but a further increase in N was noticed. In addition, after each of the reactions, the peak asymmetries decreased by ca. 15%, for a total of ca. 30%. The columns were then subjected twice to methanol at 100°C for 5h at 1 mL/min. After these stability tests, the values of k remained roughly constant, the number of plates increased, which is favorable, and the asymmetries rose and then declined, where they remained below the initial values for the unfunctionalized columns. Functionalized and unfunctionalized particles were characterized by scanning electron microscopy and BET measurements, which showed no difference between the functionalized and unfunctionalized materials, and X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry (ToF-SIMS), where ToF-SIMS suggested some chemical differences between the functionalized and unfunctionalized materials. In particular ToF-SIMS suggested that the expected five-carbon fragments from DTAP exist at higher concentrations on DTAP-functionalized PGC. First principle calculations on model graphitic surfaces suggest that the first addition of a DTAP radical to the surface proceeds in an approximately isothermal or slightly favorable fashion, but that subsequent DTAP additions are then increasingly thermodynamically favorable. Thus, this analysis suggests that the direct functionalization/passivation of PGC with DTAP is plausible. Chemometric analyses of the chromatographic and ToF-SIMS data are also presented.
authors: Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84602, USA.
authors: David S
authors: DS
authors: Jensen
authors: Vipul
authors: V
authors: Gupta
authors: Rebecca E
authors: RE
authors: Olsen
authors: Alex T
authors: AT
authors: Miller
authors: Robert C
authors: RC
authors: Davis
authors: Daniel H
authors: DH
authors: Ess
authors: Zihua
authors: Z
authors: Zhu
authors: Michael A
authors: MA
authors: Vail
authors: Andrew E
authors: AE
authors: Dadson
authors: Matthew R
authors: MR
authors: Linford
mesh_terms: D001555:Benzene Derivatives / Q000032:analysis; D002851:Chromatography, High Pressure Liquid / Q000295:instrumentation*; D006108:Graphite / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D010545:Peroxides / Q000737:chemistry*; D010636:Phenols / Q000032:analysis; D016062:Porosity; D025341:Principal Component Analysis; D013816:Thermodynamics
chemical_list: D001555:Benzene Derivatives; D010545:Peroxides; D010636:Phenols; D006108:Graphite