| A major limitation of inductively coupled plasma optical emission spectrometry (ICP-OES) systems has been the almost exclusive use of pneumatic nebulization to introduce samples into the plasma. This sample introduction method requires that samples either be liquid or be converted to a solution form and that normally several milliliters of sample be available. A flexible new sample introduction system for the direct analysis of a wide range of samples including small liquid volumes, botanical powders, coal, coal ash, oil, and a variety of other solids has been developed.;With this system, sample-carrying cups can be sequentially and automatically inserted into an ICP discharge using a pneumatically controlled transport device. An unlimited number of samples can be handled, since sample cup carousels are readily exchanged without disturbing ICP operation. This pneumatic delivery system also lends itself to modification for remote sampling applications (e.g. in toxic environments).;The sample is pneumatically delivered to a simple mechanical positioner located just under a modified ICP torch. This device allows for sample cup location relative to the plasma discharge to be programmed through "dry," "ash," and "vaporize" cycles. Results obtained with a new CW CO;This system also incorporates a novel water-cooled torch and argon/oxygen or argon/hydrogen mixed gas coolant flow. With the argon/oxygen mixture, it is possible to totally consume graphite cups containing biological samples in a controlled fashion. Temporal data reveals enhanced volatilization of specific analytes from the graphite cups in an argon/oxygen discharge relative to a pure argon plasma.;In an effort to increase the precision of analysis for elements such as manganese and nickel, volatilization of analyte from molybdenum, tantalum, and tungsten sample cups in an argon/hydrogen plasma was studied. Tungsten cups gave the best precision for multielement standard solutions. This data is superior to that obtained for the same solutions analyzed by insertion of graphite cups into an argon/oxygen plasma. These results suggest that in certain cases where total sample consumption is not necessary, the metal cup/reducing plasma technique may be more appropriate. |
