| Atomic emission spectroscopy (AES) is a widely used technique for sensitive, rapid multielement analysis. However, the reliability of the analytical information obtained from AES is limited by the spectroscopic selectivity of the instrumentation used in making the measurement. In Part I of this dissertation, selective spectral-line modulation (SLM) is introduced as a novel approach for improving selectivity in the measurement of elemental atomic emission from high-temperature flames and plasmas. With SLM, emitted spectral-lines from specified elements are selectively modulated while other forms of emitted radiation remain unmodulated. Frequency-selective detection then responds only to the "tagged" lines. Because of a very narrow portion ((TURN) 0.005 nm) of the spectrum is detected with SLM, a high degree of freedom from all types of spectral interferences is realized. Unambiguous spectral-line identification, even in very complex spectra, is greatly simplified. Moreover, multielement analysis is possible with SLM, for spectral lines emitted by several elements can be simultaneously modulated and detected. Unfortunately, customary sensitivity of AES is reduced somewhat with SLM and must be traded for element specificity and freedom from spectral interference.;Replacement ion chromatography (RIC) is introduced in Part II of this thesis as a novel detection technique for sensitively determining the concentration of ions separated by ion chromatography. In RIC, analytically important ions (cations and anions) are stoichiometrically replaced in the flowing chromatographic effluent with an ion that can be measured sensitively by spectroscopic techniques such as AES.;Such a detector, which can be dedicated to quantitating the replacement-ion concentration, proves to have better sensitivity for ion analysis than conductometric detectors. . . . (Author's abstract exceeds stipulated maximum length. Discontinued here with permission of author.) UMI.;The sensitive determination of aqueous non-metal ions is difficult by AES and is currently not practiced routinely. Often, a separation technique termed ion chromatography (IC) is used instead to separate such ions by ion-exchange principles. The chromatographic separation affords a high degree of ion (elemental) specificity. Once separated, the analyte ions can then be measured quantitatively by conductometric methods. Such conductivity measurements are commonly plagued with limited sensitivity and temperature dependence. In addition, they require individual calibration for each ion to be determined. |
