Some Effects of High-Solids Matrices on the Sample Delivery System and the Meinhard Concentric Nebulizer during ICP Emission Analyses

Reports have challenged the viability of the concentric nebulizer for high-solids analyte injection in ICP spectrometers. Such samples, particularly those high in sulfates, have been said to cause emission signal drift and plasma instability due to salt deposits on the nebulizer nozzle tip which progressively obstruct argon supply to the plasma. It was of interest to test this hypothesis, particularly with respect to a comparison of the performance of a recently developed recessed capillary tip nozzle, the Meinhard Type C, with the performance of the widely used Types A and B. The aqueous test analyte contained 410 g/L hydrated aluminum sulfate with 1 mg/L manganese as internal standard. Nebulizer performance on a Perkin-Elmer ICP/5000 was monitored via the manganese emission signal and continuous readouts of the nebulizer argon flow rate and argon pressure. In each test, sample analyses continued to the point of plasma failure and instrument shutdown, after which the torch and nebulizer were removed and photographed. In all cases, failure due to salt deposits was discovered in the sample delivery tube of the torch, not in the nebulizers. However, the time before plasma failure occurred was significantly longer with the Type C nebulizer than with either the Type A or Type B units. Photographs and data tabulations are provided to illustrate these effects.