Importance of quantitative trace analysis in industry today

Abstract

Trace analysis in the industrial analytical laboratory represents a substantial portion of the overall lab workload. This paper will explore some of the kinds of analyses that are done, why they are done, and what the limitations are to our current capabilities. Industry represents the full diversity of analytical problems, and even within one company, such as BP America, important trace quantitation problems can arise from petroleum products, ceramics, minerals, biological materials, chemicals, catalysts, and, of course, environmental samples relating to all of these. It would be impossible to review all of the trace analytical methods used for such a diverse set of samples, to compare relative merits, or to in any way survey the field of trace analysis in industry. Rather, this paper looks at certain major themes that are driving the entire area, overlapping many techniques in each case. For all of the diversity of quantitative industrial trace analysis, three motivational themes seem to dominate: samples where the trace quantity provides the value to a product; samples where trace species degrade the value of a product; and, samples where trace species represent a potential hazard to human, animal or plant life. In suggesting these categories, and in the subsequent discussion, I am removing from the realm of trace analysis problems in which the analyte is in high concentration but small quantity. For some techniques these may present the same problem as low concentration trace analysis, but increasingly, we find that instrumentation has evolved considerably in the ability to handle small samples. The first category, trace quantities as key to product value, is probably most noticeable in importance today for the electronics industry. While classical chemistry recognized the importance of certain trace elements or compounds, it was the electronics industry, beginning in the earliest days of the transistor and continuing to the present, that turned this into a picoscience. Examples in other aspects of chemistry and materials science abound. Modern heterogeneous catalysts have derived selectivity and activity from trace elements. Metallurgists, ceramists, and polymer scientists can bring about significant improvements in material properties by adding trace quantities of appropriate substances. The analytical challenge here has been considerable. In many cases we are asked to analyze very low levels, with a high degree of quantitation, and on solid phases. It is the latter point that probably has provided the greatest challenges and the most innovative solutions. The triumphs of SIMS, an industrial innovation, despite its being a destructive technique, are to be particularly noted in this field. Many advances have also come from Fourier transform techniques, in NMR, IR, and mass spectrometry. Even in such well developed areas as atomic spectroscopy, the introduction of low temperature plasma ashing and acid digestion using sealed Teflon vessels has permitted dissolution of solids with almost no loss or contamination. There still remains much to be done. While SIMS provides some depth profiling, we continue to be challenged by deep interfaces. These are of great importance, but analytical methodology for reaching and analyzing them is decades behind our ability to deal with surfaces. The second area is also a well established problem in the electronics industry, but pervades much of the rest of chemistry. While some trace elements provide catalyst selectivity, others are potent catalyst poisons. Relatively low levels of metals in coke (iron, nickel, vanadium) result in substantial drops