Polycyclic aromatic hydrocarbon analysis elution

An alternative way of eliminating water in the RPLC eluent is to introduce an SPE trapping column after the LC column (88, 99). After a post-column addition of water (to prevent breakthrough of the less retained compounds), the fraction that elutes from the RPLC column is trapped on to a short-column which is usually packed with polymeric sorbent. This system can use mobile phases containing salts, buffers or ion-pair reagents which can not be introduced directly into the GC unit. This system has been successfully applied, for example, to the analysis of polycyclic aromatic hydrocarbons (PAHs) in water samples (99). 

Fractions 3 and 4 from the tar trap tar, which primarily contained polycyclic aromatic hydrocarbons and their alkylated derivatives, were combined and subfractionated on a silica gel column. In sequential elution, toluene eluted 46 percent of the mass (subfraction A), propanol eluted 48 percent (subfraction B), methanol eluted 3 percent (subfraction C) and 3 percent was recovered by washing the silica gel with tetrahydrofuran (subtraction D). The toluene subfraction was found by GC/MS analysis to consist of a series of PAH, both parent compounds and numerous methylated derivatives. In addition, the heterocyclic compound dibenzothiophene was present as a major peak. Tentative identifications are listed in Table IX. Compounds whose identifications were confirmed by GC retention time comparisons with standards are noted. Although the identities of many of the individual PAHs have not been confirmed, it is clear that most of the subtraction is PAH in nature. 

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