Exploring Different Approaches to Improve the Analytical Performance of Inductively Coupled Plasma Optical Emission Spectrometry with Pneumatic Nebulization or Electrothermal Vaporization
Al Hejami, Ahmed
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This thesis is aimed at exploring new diverse approaches for improving the analytical performance of inductively coupled plasma (ICP) optical emission spectrometry (OES) with pneumatic nebulization (PN) or electrothermal vaporization (ETV). First, a new infrared (IR)-heated PN system was developed to enhance sample transport efficiency and concurrently improve sensitivity, detection limit and plasma robustness of ICPOES. A cyclonic spray chamber was modified so as to insert an IR lamp heater inside it. The modified cyclonic (MC) spray chamber was heated up to 150 °C. Using a pre-evaporation tube (PET) between the MC spray chamber and the plasma torch was also investigated. Under optimum operating conditions, a 2-5 fold improvement in sensitivity and 2-7 fold improvement in detection limit were achieved for 26 elements compared to conventional PN at room temperature. Second, the analytical performance of ICPOES was improved by IR heating of commercially available spray chambers using different types of IR heaters, namely ceramic block and ceramic beaded IR heaters. For 29 elements, the detection limit improved by, on average, 2-3 fold with the rope heater and 5-10 fold with the block heater. All IR-heated systems enabled the accurate analysis of a certified reference material (CRM) of waste water. Third, the effect of IR heating of the top surface of a cyclonic spray chamber on the analytical performance of ICPOES was investigated. Upon IR heating (up to 150 °C), sensitivity and detection limit improved by 3-5 fold and 4-12 fold, respectively compared to those with the same system at room temperature. The IR-heated system allowed the accurate multi-elemental analysis of two CRMs. Finally, addition of H2, N2 or water vapour to the central gas flow of the plasma was assessed to enhance the analytical performance of solid sampling (SS) ETV-ICPOES. Sensitivity and detection limit were significantly improved upon sheathing the sample aerosol with H2, N2 or water vapour for 11 elements compared to those with conventional SS-ETV-ICPOES. To the best of the author’s knowledge, this is the first published study of the effect of adding N2 to the central gas flow of the plasma on the analytical performance of SS-ETV-ICPOES.