Determination of Polycyclic Aromatic Hydrocarbons by HPLC with Spectrofluorimetric Detection and Wavelength Programming

Removal of naphthalene from aqueous systems by poly(divinylbenzene) and poly(methyl methacrylate-divinylbenzene) resins

Treatment of the oily wastewater from crude oil extraction is a growing challenge due to rising concern for the environment. Polyaromatic hydrocarbons (PAHs) deserve special attention because of their high toxicity. There is a need to develop processes able to minimize the discharge of these compounds and analytic techniques to monitor the levels of PAHs in aqueous media. In this study poly(methyl methacrylate-divinylbenzene) (MMA-DVB) and poly(divinylbenzene) (DVB) were assessed with respect to their capacity to retain naphthalene (NAF) in continuous flow and batch processes (adsorption equilibrium and kinetics). The analytic techniques applied were gas chromatography and spectrofluorimetry, which was adapted for quantification of NAF. The batch adsorption studies showed that DVB is more efficient in adsorption than MMA-DVB, and the Freundlich model and pseudo-second-order model better fitted the equilibrium data and adsorption kinetics, respectively. The elution results showed that both resins are highly efficient in removing NAF, with DVB outperforming MMA-DVB. However, MMA is cheaper raw material, making MMA-DVB more competitive for treatment of oily wastewater. The resins were regenerated by eluting about 7.2 and 2.5 L of methanol:water (70:30 v/v), respectively for DVB and MMA-DVB. Regarding to the useful life after regeneration, the resins presented a reduction about 30%, relating to zero concentration of NAF.

Determination of polyaromatic hydrocarbons in river water using a sorbent consisting of removable octadecyltrimethylammonium ions attached to cation exchange silica in conjunction with commercial C18 silica

An application that highlights the usefulness of a solid phase extraction sorbent having a removable surfactant "stationary phase" is introduced. Polyaromatic hydrocarbons (PAHs) efficiently trap on commercially available non-polar sorbents (i.e., C(18) silica). However, solvents that are necessary to break strong hydrophobic interactions between the analyte and sorbent are harmful and incompatible for direct introduction into a reversed phase liquid chromatographic setup. In the presented approach, the entire "stationary phase"-analyte association is removed, resulting in very efficient elutions with a final extract that is mild and reversed phase liquid chromatographic compatible. Commercial C(18) silica was placed adjacent to this sorbent to provide more efficient trapping of less hydrophobic PAHs. PAHs were preconcentrated from river water and were determined using fluorescence detection coupled to HPLC. Detection limits for all PAHs examined were in the sub [micro sign]g L(-1) level.

Solid-phase extraction of polycyclic aromatic compounds

Solid-phase extraction (SPE) for two groups of polyaromatic compounds--polycyclic aromatic hydrocarbons and naphthalenesulfonates--with completely different problems in the extraction process are reviewed. The sorbents used in each case and the different steps of SPE are studied. Particular problems encountered in the SPE of each group are described. Adsorption problems of PAHs which require an organic solvent or a surfactant to be added to the sample are explained. The need of ion-pair solid-phase extraction for extracting naphthalenesulfonates and the influence of the inorganic species in the extraction are discussed. The on-line systems are described for both group of compounds.

High-sensitivity chromatographic detector incorporating three-dimensional charge coupled device fluorimetry

This article describes a detector for liquid chromatography that provides three-dimensional, excitation-emission-intensity data of fluorescent compounds. The instrument achieves multi-wavelength excitation by employing a polychromator that disperses radiation along the vertical portion of a quartz capillary flow cell. The ensuing sample fluorescence is collected in the horizontal plane and dispersed using an emission polychromator to form a focused two-dimensional excitation-emission image at a charge coupled device (CCD) pixel array. Each vertical pixel equates to a narrowly defined excitation wavelength band, whilst horizontal pixels equate to corresponding emission wavelengths, with the intensity of light encroaching onto the CCD pixel elements providing the third-dimensional variable in the measurement. It is shown that the extreme sensitivity of CCD detection coupled to the dual polychromator arrangement makes possible the collection of fluorescence excitation-emission-intensity data of polycyclic aromatic hydrocarbons in a flow stream in less than 0.05 s with nanogram per millilitre limits of detection.