Improvements in methods and apparatus relating to inductively coupled plasma atomic fluorescence spectrometry
This thesis describes a study of the technique and development of a system known as ASIA (Atomiser, Source, Inductively Coupled Plasmas (ICPs) in Atomic fluorescence spectrometry). Copper, nickel and lead boosted-discharge hollow-cathode lamps (BDHCLs), have been compared with the ICP, as excitation sources. A detailed study of the spectra of nickel and lead was performed. No evidence was found for the differences in the radiances between the two sources when the copper lamp was overrun. Although the lamps gave rise to lower blank standard deviation values, the detection limits were worse with the lamp source compared to ICP source. The modified Optica CF4 monochromator originally used, has been replaced by a Bentham Instruments computer controlled monochromator with better light gathering power. The optical arrangement for gathering the fluorescent radiation has also been re-designed. The performance of the modified system has been studied, based on detection limits (DLs), for a number of elements. In general, an improvement of 2 to 3 times in DLs is achieved. Further, improvements in the detection limits for molybdenum and tungsten have been achieved with the development of an on-line preconcentration procedure using a miniature column of Amberlite (IRA-93) anion-exchange resin. A heated spray chamber desolvation system has been evaluated as a sample introduction device for atomiser and source plasmas but, unfortunately the results obtained with the device were unsatisfactory. Problems included periodic instability of the plasmas and salt deposition on the inner walls of the spray chamber when high concentration solutions were aspirated. Also, a brief study of the feasibility of an aerosol modulation device has been performed. Finally, an interference study has been made to investigate the interference effects of high concentrations of interferent elements on a number of analyte elements. Spectral scans were obtained to visualise any possible interference effect. No spectral interference effect was observed on any of the analyte elements due to the interferent elements studied.