I have some measurements at the As edge of As(V) adsorbed onto pure goethite (alfa-FeOOH), Mn partially substituted Goethite (alfa-Mn,Fe.OOH), Al substituted goethite (alfa-Al,FeOOH) and Mn and Al goethite (alfa-Al,Mn,FeOOH) The EXAFS signals change from one spectrum to another. I have refined the distances As-Fe on pure goethite, but when I try to refine Mn-FeOOH or Al,FeOOH, the analysis gets more difficult because As forms different complexes with Al and Fe. Unfortunately for me is almost impossible to have the pure phases alfa-MnOOH or alfa-AlOOH, and measured the As adsorbed. How can I analyze the spectra and have some knowledge about the As-surface complexes formed? Thanks, Elsa Dra. Elsa E. Sileo Solidos Inorganicos INQUIMAE - Dto. Qca. Inorganica, Analitica y Qca. Fisica; FCEN, UBA Int. Güiraldes 2160, Pabellón 2, Piso 3, Ciudad Universitaria - C1428EHA CABA - Argentina Tel: (54 11) 4576 3380 ext. 113 Fax: (54 11) 4576 3341 e-mail: sileo@qi.fcen.uba.ar