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Water-soluble organic compounds (WSOC) often represent a large fraction of the total organic mass found in the atmospheric aerosol. They play a very important role in determining the ability of aerosol particles to act as cloud condensation nuclei (CCN), influencing cloud and fog formation and cloud albedo. Molecular characterization of WSOC in fogwater samples was achieved using a two-stage ion-trap mass spectrometer equipped with electrospray ionization (ESIMS/MS). Negative ionization conditions in the electrospray interface finalized our characterization of the acidic fraction of WSOC that comprises both mono- and di-carboxylic acids and polycarboxylic acids for which a similarity was suggested with naturally occurring humic (or fulvic) acids, and which are sometimes referred to in the literature as humic-like substances (HULIS). Molecular structure elucidation was accomplished using several model compounds and exploiting mass spectral resolution for compound separation. Single compound identification ...

A new solid-phase extraction on-line device for micro-HPLC is presented. This device optimizes the injection of very dilute samples into a packed capillary column. It consists of two capillary, reversed-phase, HPLC columns of different length that can be linked together as a single chromatographic column. The first segment, only 2 cm long is connected to the HPLC injector. When disconnected from the longer column, several milliliters of an aqueous sample can be passed through at a high flow rate for fast trapping. On the basis of the retention mechanism, all suitable compounds are focused on the short column head in a sharp band. As soon as the chromatographic column is recomposed, the trapped analytes are eluted and separated at the optimal flow rate and gradient conditions. Due to the high preconcentration factor, trace-level analysis can be performed successfully. Different classes of analytes of various polarities and molecular weights can be determined, depending on the stationary phase and on the detector used. Some pesticides belonging to different classes were chosen to evaluate the performance of the device using an electron ionization mass spectrometer as HPLC detector. A fungicide in an irrigation canal water was determined at a concentration level of 4.5 microg x L(-1).

A new ion-interaction micro-HPLC method, for the simultaneous separation of acidic and base-neutral pesticides, was coupled to a capillary-scale particle beam LC/MS interface for EI mass spectrometric detection of the analytes. The method was employed for analysis of tap water in which a large number of functionally different pesticides can be determined in a single run. Capillary-scale technology of the LC/MS apparatus yields full compatibility with hexylammonium phosphate, a nonvolatile salt used as ion-interaction reagent in the HPLC mobile phase, and provides an excellent sensitivity with instrument detection limits (IDLs) ranging between 0.07 and 0.7 ng in SIM mode. Method sensitivity lower than 0.1 ppb in water was achieved using a large-volume injection technique specifically developed for capillary columns typical flow rates.