Investigations of the effects of aerosol flow on discrete sample signals and development of condensation nucleation light scattering detection for ion chromatography

This dissertation covers two areas of research involving aerosols. The first part (chapters 2 and 3) deals with the effects of aerosol dispersion in the spray chamber on discrete signals using inductively-coupled plasma-atomic emission spectrometry (ICP-AES) and condensation nucleation light scattering detection (CNLSD) methods. Dispersion in the aerosol phase is investigated by considering the influence of particle size, post-baffle volume, residence time and recirculation phenomenon around the nebulizer on peak parameters. As is known from liquid phase transport, dispersion decreases resolution and increases detection limits. Results and information obtained from these chapters were applied to experiments involving CNLSD coupled to liquid chromatography (LC) separations, with the goal of reducing peak dispersion in chromatograms.; The second part of this research involves the application of CNLSD to LC. CNLSD is a universal detector as it requires only the nonvolatility of the analyte with respect to the eluent for it to be sensitively detected. It is a detection technique where the dry particles generated in the system are increased in size by the condensation of butanol onto these particles, making them efficient-light-scattering droplets. The amount of light scattered is proportional to the concentration of the analyte enabling quantification.; The coupling of CNLSD to ion chromatography is reported in chapters 4 and 5. Nonvolatile contaminants from the eluent were minimized by using a precolumn scavenger column and the background levels were further controlled by using diffusion screens. Excellent detection was achieved for cations with limits of detection (LODs) for the alkali, alkaline, and transition metal ions at low ng/mL levels. For organic ions of protonated biogenic amines, LODs were also at the low ng/mL level, or well below the LODs reported by UV absorbance and integrated pulse amperometric detection methods. The advantages of CNLSD over conventional conductivity detection are shorter analysis times and the elimination of suppressors. Unlike UV absorbance detection, derivatization is not needed. With anions, sensitivity was limited by the high background levels resulting from the nonvolatile contaminants.; In chapter 6, sugars, which are not sensitively detected by refractive index (RI) and difficult to detect by UV absorbance, are well detected by CNLSD. The LODs were comparable to electrochemical detection but with the added advantage of the absence of complex reaction at the electrode's surface for detection.