Effect of C18 surface coverage on selectivity in reversed-phase liquid chromatography of polycyclic aromatic hydrocarbons

Abstract

1479 (15) Colby, B. N.; Rosecrance, A. E.; Colby, M. E. Anal. Chem. 1981, 53, (16) Glaser, J. A.; Foerst, D. L.; McKee, G. D.; Quave, s. A,; Budde, W. L. (13) Budde, W. L.: Eichelberger, J. W. "Performance Tests for the Evaluament and Laboratories"; Environmental Protection Agency Report EPA-600/4-80-025, April 1980. (14) Sauter, A. D.; Betowskl, L. D.: Smith, T. R.; Strickler, V. A,; Belmer, R. G.; Colby, B. N.; Wllkinson, J. E. HRC CC J . High Resolut. Chromatogr. Chromatogr. Commun, 1981, 4 , 366-384. tion of Computerized Gas ChromatographylMass Spectrometry Equip-1907-1 91 1 I Envrron. Sci. Techno/. 1981, 15, Recent studles trave reported selectlvlty dlfferences for POlycyclic aromatllc hydrocarbons (PAH) on dlff erent octadecylsllane (C18) reversed-phase llquld chromatographlc columns. I n this paper the differences in llquld chromatographic selectlvllty for various Cts columns were correlated with dlfferences In C,, surface coverage data (as determlned from elemental rinalysis and specific surface area measurements on the C,, modlfled slllca). Slgnlflcant dlfferences In selectlvlty were observed for selected PAH and polyphenyl arenes on monornerlc vs,, polymeric C,, materials. Selectlvlty factors for 50 PAH, alkyksubstltuted PAH, polyphenyl arenes, and polycycllc aromatic sulfur heterocycles were determlned on columns from the same manufacturer from seven dlfferent lots of C,, material with dlfferent C,, surface concentratlons.I n addltlon to priovldlng information concerning the contrlbutlon of C18 surface coverage to retentlon rind selectlvlty In the LC separatlon olf these compounds, these studies provide useful Information regarding the selectlon of the approprlate column to optlniize the separatlon of 'selected polycycllc aromatlc compounds.Reversed-phase liquid chromatography (LC) on chemically bonded octadecylsilane (C18) stationary phases is by far the most popular LC mode for the separation of polycyclic aromatic hydrocarbons (PAH). Reversed-phase LC on Cls phases provides excellent selectivity for the separation of PAH isomers and alkyl-substituted PAH isomers ( I ) . Recently, reversed-phase LC on C18 columns has been specified as the method of choice for the analysis of aqueous effluents for the determination of the 16 PAH on the U.S. Environmental Protection Agency's priority pollutant list (2). In addition to the environmental interest in the determination of PAN by LC, PAH are excellent nonpolar solutes for use in the investigation of reversed-phase LC retention mechanisms.Since Schmit et al. (3) i h t described the separation of PAN on a chemically bonded CI8 phase in 1971, numerous reports of LC retention data for PAH on various C18 columns have appeared. Recent studies by Wise et al. (4), Ogan and Katz (5,6), Colmsjo arid MacDonald (7), and Amos (8) found that Cl8 columns from various manufacturertr not only provided different separation efficiencies but often provided different selectivities and iretention characteristics for PAH. In these studies, attention was focused on three groups of...

Chemometric studies of polycyclic aromatic hydrocarbon shape selectivity in reversed-phase liquid chromatography

“…In general, greater discrimination among PAH isomers has been observed with the higher bonding density (5 to 6 µmol m -2 ) polymeric stationary phases assembled from polymerized alkylsilanes bound to a silica surface in contrast to the lower bonding density (2 to 3.5 µmol m -2 ) monomeric phases, which are prepared with monofunctional alkylsilanes through single-bond linkages with silanols at the silica surface [14,15]. Shape selectivity among C 18 stationary phases generally increases with increasing bonding density, regardless of the type of phase (monomeric or polymeric) or the bonding chemistry used in the phase preparation [2,16]. This suggests that overall alkyl chain proximity is a major contributing factor to such shape selective processes.…”

Standard Reference Materials (SRMs) for the Determination of Polycyclic Aromatic Compounds--Twenty Years of Progress

“…As a result of this limitation, investigations were initiated at NIST to understand the influence of factors such as bondedphase type, silica-substrate characteristics, alkyl-chain length, and C 18 ligand density on selectivity of PAH separations in reversed-phase LC. The results of these investigations were published in several papers (36)(37)(38)(39)(40)(41) and summarized in several review articles (42)(43)(44)(45).…”

“…From studies of the retention behavior of over 100 PAH standards on monomeric and polymeric C 18 phases (31), several compounds were found to exhibit dramatic changes in relative retention on the two stationary phases. Based on the results of these investigations (40,47,48), a simple empirical test was developed to assess the selectivity of C 18 stationary phases for the separation of PAHs. The test is based on the relative retention of three carefully selected PAH solutes as shown in Figure 9.…”

HPLC Separation of Triacylglycerol Positional Isomers on a Polymeric ODS Column

“…In contrast, the "monomeric ODS phase" is prepared by the reaction of monofunctional silanes (i.e., dimethyloctadecylchlorosilanes) with silica gel under anhydrous conditions to cover the silica gel surface with a single layer of octadecylsilane. 10 Sander and Wise investigated the steric recognition ability of an ODS column for organic compounds. They examined the separation factor of planar and non-planar compounds using a mixture of polycyclic aromatic hydrocarbons (PAHs), dibenzo[g,p]chrysene (tetrabenzonaphthalene; TBN) and benzo[a]pyrene (BaP) on 25 different ODS columns, and proposed to classify the ODS stationary phase characters into three groups based on the value of the separation factor, aTBN/BaP, derived from the ratio of the TBN and BaP retention factors.…”