NONINVASIVE QUANTITATIVE CHROMIUM(III) SPECIATION IN NEAT SOLID MIXTURES BY EXTENDED X-RAY-ABSORPTION FINE-STRUCTURE SPECTROSCOPY

A procedure that uses extended X-ray absorption fine structure (EXAFS) spectroscopy for quantitative chromium(III) speciation in neat solid mixtures is described. The procedure uses the full, filtered EXAFS, e. g., 4 less than or equal to k less than or equal to 12 Angstrom(-1), r ather than the smaller k-range associated with a single coordination s phere. Concentration is determined by a simple correlation of full, fi ltered EXAFS of standards with full, filtered EXAFS of mixtures. Under optimized conditions, calibration curves for mixtures of Cr2O3 and Cr (NO3)(3) . 9H(2)O have slopes of 1.002, respective intercepts of -0.7% and 0.5%, and correlation coefficients of 0.9991. Fluorescence EXAFS from mixtures must be compared to fluorescence EXAFS from standards, a nd the matrices and thicknesses of standards and mixtures must be clos ely matched. Transmission EXAFS of standards must be obtained to corre ct for self-absorption effects.