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A new sample support film for small spot XRF analysis has been developed that improves detection limits by a factor of 10 over traditional polymer supports. The surface characteristics of this new film are excellent for retaining drops of sample solution in one place and allowing the solution to dry into a single spot A dimpling technique was developed to further aid in concentrating the evaporated samples to the prescribed spot size and position. The film showed good resistance to chemical attacfc from the solution, even some strong acids and bases. The detection limits achieved using micro sample XRF with the ultra thin sample support were sufficient to be a comparable alternative to ICP-MS and GFAAS for elemental analysis.

Widespread interest in light element analysis using XRF has stimulated the development of thin x-ray tube windows. Thinner windows enhance the soft x-ray output of the tube, which more efficiently excite the light elements in the sample. A computer program that calculates the effect of window thickness on light element sample fluorescence has been developed. The code uses an NIST algorithm to calculate the x-ray tube spectrum given various tube parameters such as beryllium window thickness, operating voyage, anode composition, and take-off angle. The interaction of the tube radiation with the sample matrix is modelled to provide the primary and secondary fluorescence from the sample. For x-rays in the energy region 30 - 1000 eV the mass attenuation coefficients were interpolated from the photo absorption data compilation of Henke, et al. The code also calculates the x-ray background due to coherent and incoherent scatter from the sample, as well as the contribution of such scatter to the sample fluorescence. Given the sample fluorescence and background the effect of tube window thickness on detection limits for light elements can be predicted.