Fundamental Characteristics of Thermospray Aerosols and Sample Introduction for Atomic Spectrometry

Sample introduction to inductively coupled plasma atomic emission using thermospray nebulization is studied at a fundamental level. Optimum signals and signal-to-noise ratios result from thermospray operation at temperatures which coincide with highest analyte transport (>20%). High transport levels are maintained at sample flow rates of up to 3 mL/min. On the basis of comparison with analyte transport measurements for a pneumatic nebulizer (1.5%), signal increases are less than anticipated. Measurement of primary thermospray aerosols, using Fraunhofer diffraction, indicates that the enhanced transport results from decreased particle sizes for thermospray aerosols compared with pneumatic aerosols. Solvent is more rapidly vaporized from hot thermospray aerosols, further increasing the disparity in particle sizes. On the basis of aerosol particle size data, a conceptual model for aerosol generation, which is similar to pneumatic processes, is developed for thermospray. Trends for further improvements in thermospray aerosol production are predicted.