Inductively coupled plasma laboratory experiments

This experiment presents the measurement of uranium with an inductively coupled plasma mass spectrometer (ICP-MS). In this system, a nebulizer converts the aqueous sample to an aerosol carried with argon gas. A torch heats the aerosol to vaporize and atomize the contents in quartz tubes. The atoms are ionized with an efficiency of about 95% by an RF (radiofrequency) coil. The plasma expands at a differentially-pumped air-vacuum interface into a vacuum chamber. The positive ions are focused and injected into the MS while the rest of the gas is removed by the pump. The ions are then accelerated, collected, and measured as a function of their mass. Losses at various stages, notably the vacuum interface, result in a detection efficiency of about 0.1 %, which is still sufficient to provide great sensitivity. The amounts of uranium isotopes in the sample are determined by comparisons to standards. Because different laboratories have different instruments, the instructor will provide instrument operating instmctions. Do not use the instrument until the instructor has checked the instrument and approved its use. 

The application of an inductively coupled plasma system to the determination of rare earth impurities in a pure rare earth has not to our knowledge been reported. However, preliminary experiments in our laboratories indicate that trace rare earth spectral line intensities are essentially independent of the major constituent. Thus, a calibration curve for the determination of one rare earth in a matrix may well be valid for other rare earth matrices so long as spectral line interferences do not occur. Additional comments on these observations may be found in section 4. 

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