A FLUIDIZED-BED POWDER SAMPLER FOR INDUCTIVELY COUPLED PLASMA EMISSION - HARDWARE DESIGN, PERFORMANCE EVALUATION WITH GEOLOGICAL REFERENCE MATERIALS

A fluidized-bed sampling device for the direct analysis of solid powders by plasma emission and plasma mass spectrometry is described. The powder sample is fluidized by a combination of mechanical and gas flow actions. Horizontal motion of the sample vial is shown to be an effective means of mixing and suspending the particulate material. Gas flow controls ensure that a minimal change in the plasma operating condition occurs during sample exchange, and that the sample powder is not disturbed by high gas flows during these operations. No mechanical valve or flow controller is in the path of the gas/particulate mixture between the sampler and the plasma. A device for automatic sample change is described. Sample carryover was less than 5% on a blank measured immediately after a geological reference sample (NIM-D), and below 3% on subsequent measurements. Wavelength scans for minor elements in NIM-L, NIM-P and NIM-D geological samples are reported. The tendency of fine particles to agglomerate by electrostatic forces can be reduced by mixing sample and uniform sized silica (30 μm diameter) 1:1, by weight. The mixing of the sample with large, uniform-sized particles of silica offered a practical approach for addition of internal standard elements, minimized the matrix-specific mechanical characteristics of the sample, and yielded a mixture with properties suitable for fluidization. © 1990.