Conny Östman

Retention characteristics of some selected halogenated environmental pollutants in silica and bonded normal-phase liquid chromatography

Abstract Seven bonded stationary phases and unmodified silica were investigated regarding their retention properties towards a number of halogenated environmental pollutants including 26 individual polychlorinated biphenyl congeners. No simple retention-structure relationship was found for the polychlorinated biphenyls but a number of phases demonstrated similar selectivities towards the investigated congeners. The retention of compounds with aliphatic carbons were substantially influenced by the presence of hydrogens possessing acidic properties due to inductive effects of adjacent chlorine or oxygen atoms. Solute molecule ether oxygens were shown to promote retention by hydrogen bonding only on silica and phenylpropyl silica. Polybrominated diphenyl ethers demonstrated a complex retention behaviour on the different stationary phases. Indication was found that bromine may be directly involved in the retention mechanism.

Retention mechanisms of polycylic aromatic nitrogen heterocyclics on bonded amino phases in normal-phase liquid chromatography

Two aminoalkyl bonded phases, aminopropylsilica and dimenthylaminopropylsilica, operated in the normal-phase mode were investigated regarding the retention mechanisms of polycyclic aromatic nitrogen heterocyclics (PANHs). By blocking active interaction sites with methyl substituents, the retention mechanisms could be ascertained. The bonded functional groups of the aminoalkyl stationary phases were found to be the primary adsorption sites. Hydrogen bonding was found to be the dominant retention mechanism for carbazole-type PANHs on both stationary phases and for acridine-type PANHs on the aminopropyl phase. For acridine-type PANHs on dimethylaminopropylsilica, retention was found to be mainly due to electron donor-acceptor interaction. Residual silanols on the stationary phase support material on these non-end-capped bonded phases were found to contribute only slightly to the retention of both acridine- and carbazole-type PANHs. A strong dependence of retention on steric hindrance of the n-electrons on the nitrogen of acridine-type solutes was shown. Further, the necessity to consider not only the polarity and solvent strength but also the selectivity of the mobile phase is demonstrated.

Fractionation of non-ortho-substituted toxic polychlorinated biphenyls on two nitro-containing liquid chromatographic stationary phases

Abstract Two liquid Chromatographic stationary phases, dinitroanilinopropylsilica (DNAP) and tetranitrofluorenimino-propylsilica (TENF), are demonstrated to retain selectively the toxic non- ortho -chlorobiphenyl congeners CB-77, CB-126 and CB-169. On the DNAP column, these three congeners elute as a single peak. With hexane as mobile phase all eighteen tested chlorobiphenyl congeners are eluted within 13 min. Carryover effects of CBs in HPLC systems are discussed. To demonstrate the isolation of the three congeners, a sample of Aroclor 1254 was fractionated and analysed by GC with electron-capture detection.

Separation of polycyclic aromatic compounds from complex oil samples using bonded phase backflush h.p.l.c. and g.c.-m.s. techniques

Abstract A novel method for the isolation of polycyclic aromatic compounds (PAC) from complex samples is presented. The method is a combination of fast separation on a short silica column and automated bonded normal phase h.p.l.c. utilizing a backflush technique. Liquid-liquid extraction with dimethylsulphoxide is added as a final step for samples of high complexity. Isolation and subsequent analysis by capillary g.c. is completed within 90 min. The method has been applied to the analysis of petroleum-derived materials, shale oil and solvent-refined coal, and is demonstrated using samples of a petroleum crude oil and of used crankcase oil.