Direct analysis of liquid and solid microsamples using a capacitively coupled microwave plasma atomic emission spectrometer

The ultimate goal of the research is the trace multielement determination of microsamples. This is accomplished using a capacitively coupled microwave plasma atomic emission spectrometer. The plasma is used as an atomization source, and the resulting emission is analyzed with an echelle spectrometer with a charge injection device for detection. A sample cup is built into the electrode on which the plasma is generated which holds the discrete amount of the microsample to be analyzed. These amounts are generally five microliters for liquids or one-half milligram of solid material.;The system has been evaluated by a series of optimization studies for such parameters as applied power, plasma gas flow rates, and electrode design. Following system optimization, a series of aqueous calibration standards were run for single elements to evaluate the performance of the system. Detection limits are generally in the low part-per-billion range with precision of less than 10 percent. In addition, samples such as sweat and some certified reference materials have been analyzed to determine the applicability of the technique to real samples. Preliminary results for real samples were promising, although the accuracy of the method worsens near the detection limits. Preliminary work in the area of direct solids analysis is also promising, with linear calibration and detection limits in the low parts-per-million range. However, emission signal reproducibility is a problem with the solid samples, and some of the more refractory elements in both solids and liquids can not be analyzed using this system.;This technique is unique because of its ability to perform simultaneous multielement analysis on solid or liquid discrete microsamples without the need to change the system or alter the conditions in any way. For liquid samples, the technique has detection limits similar to or, slightly higher than similar atomic emission techniques. For solids analysis, few techniques at present have attempted analyzing microsamples without the need for sample preparation, with the additional capability of multielement analysis. The capacitively coupled microwave plasma atomic emission spectrometer is a promising tool in the analysis of real microsamples.