Some fundamental considerations on analytical high-frequency plasmas.

Several possible models for plasmas, and their fundamental background, are discussed. The recent literature on investigations of fundamental plasma models and plasma parameters is reviewed.

Trace analysis by microwave excitation of sealed samples-III Determination of 0.005-25 ng of Te and 0.25-25 ng of Se in 0.5 ml of aqueous solution.

Traces of tellurium and selenium can be determined by optical emission spectrometry using microwave exitation in electrodeless discharge lamps. In 0.5 ml aqueous solution samples, freeze-dried in electrodeless discharge lamps, 10(-5) ppm Te and 5 x 10(-4) ppm Se can be determined with a relative deviation of about 20%.

Trace analysis by microwave excitation of sealed samples-II determination of 4-100 pg of Cd, In and Tl in 0.5 ml of aqueous solutions.

Trace analysis by optical emission spectrometry by microwave excitation of sealed samples has been improved by use of H(2) as a filler-gas and of BiI(3) as a matrix. It was found that the selection of suitable quartz for the manufacture of the discharge lamps is important. Limits of determination of 4 pg in 0.

The error in absorption measurements caused by the use of non-monochromatic light-III Application to linear calibration curves.

When in spectrophotometry the absorption is measured with non-monochromatic light, a curved calibration curve is often obtained. Some errors are introduced if a linear calibration curve is still used. The magnitude of these errors has been calculated.