Surface chemistry of lanthanum chromite powders II. Multivariate data modelling of the isoelectric point by the use of surface composition data achieved from X-ray photoelectron spectroscopy measurements |
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Authors: | G. Stakkestad B. Grung J. Sjöblom T. Sigvartsen |
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Affiliation: | (1) Prototech AS, Fantoftveien 38 N-5036 Fantoft, Norway, NO;(2) Department of Chemistry University of Bergen N-5007 Bergen, Norway, NO |
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Abstract: | Electrophoretic mobility measurements and X-ray photoelectron spectroscopy (XPS) analysis have been performed on several lanthanum chromite powders with different dopants. Principal component analysis of both deconvoluted XPS data and differentiated overall XPS spectra showed a clustering of the powders. From loading plots it was seen that high amounts of La and O on the surface gave highest isoelectric points (IEP). Partial-least-squares, multivariate response modelling was used to calibrate the IEPs from both deconvoluted XPS data and from differentiated overall XPS spectra. The best model was obtained when second-order differentiated overall XPS spectra were used, with an average predictive error of pH ± 0.25. This is promising considering that the IEP has been determined with an accuracy of pHIEP± 0.3. When deconvoluted data was used, the average predictive error rose to pH ± 1.1. It is therefore an advantage to use multivariate data analysis which is a nonsubjective latent variable decomposing technique in contrast to deconvolution which is an even more time-consuming method for calibration of IEP values from XPS. Received: 8 October 1998 Accepted in revised form: 27 January 1999 |
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Keywords: | Lanthanum chromite powder Electrophoretic mobility X-ray photoelectron spectroscopy Multivariate data analysis |
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