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

Volume 42, Number 7 (Oct. 1988) Page 1221-1228

Prell, L.J.; Koirtyohann, S.R.

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 (<0.4 μm), with a total sample transport rate of about 0.5 μg/s. 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.