European Community Directive 2002∕95∕EC restricts the use of certain hazardous substances in electrical and electronic equipment. In particular, restrictions are placed on lead, mercury, cadmium, hexavalent chromium, and bromine (in polybrominated biphenyls or polybrominated diphenyl ethers). XRF is a convenient method for detecting the presence and measuring the amounts of these elements. Reliably quantifying all of these elements in plastics typically requires a large number of standards that are not yet readily available. Because of the light element matrix, using a “standardless” fundamental parameters method requires some reliance on the primary beam scatter, complicating the analysis algorithm and increasing the uncertainty. We have tested a simplified fundamental parameters method that determines the matrix via difference, requiring only one standard. The method was tested on a series of reference materials containing all of the regulated elements in a variety of plastic resins. One multi-element reference standard was used. It was necessary to include all of the additives in the specimens to achieve good quantitative accuracy. In addition, the scattered primary intensity was used in one set of tests to compensate for variations in specimen thickness. This thickness compensation was necessary to get acceptable results for Cd. Results were very promising, with average relative errors and relative standard deviations of about 10%.

Artifacts are the nemesis of trace element analysis in electron-excited energy dispersive X-ray spectrometry. Peaks that result from nonideal behavior in the detector or sample can fool even an experienced microanalyst into believing that they have trace amounts of an element that is not present. Many artifacts, such as the Si escape peak, absorption edges, and coincidence peaks, can be traced to the detector. Others, such as secondary fluorescence peaks and scatter peaks, can be traced to the sample. We have identified a new sample-dependent artifact that we attribute to Compton scattering of energetic X-rays generated in a small feature and subsequently scattered from a low atomic number matrix. It seems likely that this artifact has not previously been reported because it only occurs under specific conditions and represents a relatively small signal. However, with the advent of silicon drift detectors and their utility for trace element analysis, we anticipate that more people will observe it and possibly misidentify it. Though small, the artifact is not inconsequential. Under some conditions, it is possible to mistakenly identify the Compton scatter artifact as approximately 1% of an element that is not present.