Analytical Performance and Transport Studies Using Spark Sampling Followed by ICP Excitation with a Sequential Spectrometer

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Abstract
It was established that a high-voltage spark is a viable method of sampling iron and aluminum-based alloys using a sequential spectrometer ICP. Calibration curves were linear over at least four orders of magnitude, detection limits were in the parts per million range in the solid, and precisions of 1–3% were readily demonstrated when the base metal was used as an internal standard. Fifteen elements could be determined in a three-minute burn. The best analytical performance was obtained when the gas flow sweeping particles to the plasma passed through the counter electrode. Experiments with a cascade impactor showed that most of the material reaching the plasma was in small particles (. Particles reaching the plasma were examined by the scanning electron microscope and appeared to be mostly aggregates of very small spheres of 500–1500 Å diameter. Under nonoptimum conditions, large spheres (∼1–5 μm diameter) and ablated material of irregular shape made up a significant amount of the transported material. The analytical performance is affected by particle size distribution, particle type, and sample transport rates.