Laser induced breakdown spectroscopy of aqueous solutions: Applications and matrix interferences

Laser induced breakdown spectroscopy (LIBS) has evolved over the past 40 years into a useful tool for elemental analysis applicable to solid, liquid, and gas phase samples. LIBS analysis is often performed by focusing pulsed laser radiation onto a sample to ablate material that is atomized and thermally excited in the resulting micro-plasma to emit characteristic radiation. Each element can be uniquely identified by the frequency of the emitted light for qualitative applications or the relative intensity of the light for quantitative analysis. LIBS has been extensively used for elemental determinations in solids due to the convenience of combined sampling and excitation compared to more common atomic spectroscopy techniques that require lengthy preparation procedures prior to analysis. In contrast, applications of LIBS to aqueous matrices have been less common, primarily due to inferior analytical performance compared to traditional laboratory methods. Since these methods are confined to the laboratory, a strong motivation for developing LIBS methods for aqueous matrices is remote, on-site, and in situ applications where the ability to perform the measurement outweighs the compromise in performance.; As developments in LIBS continue to grow and applications for aqueous solutions become more widespread, identification of matrix induced errors becomes more important. Although significant literature exists regarding matrix errors in solid samples, matrix errors in aqueous samples have received little attention. This dissertation addresses quantitative elemental analysis in various matrices known to cause interferences in traditional flame or plasma techniques with emphasis on sodium and potassium matrices since these are likely to be encountered in remote or in situ analyses.; Development of a LIBS method for reliable quantitative analysis of aqueous solutions following freezing is also described. The analytical performance of this method is evaluated and the dependence of signal-to-noise ratio for several analytes is described with varying experimental conditions. Development of a method of internal standards is discussed and applied to correct various analytical concerns realized in analysis of ice samples. In addition, the internal standard method is shown to compensate for various matrix-induced errors as well.