MATHEMATICAL ALIGNMENT OF WAVELENGTH-SHIFTED OPTICAL-SPECTRA FOR QUALITATIVE AND QUANTITATIVE-ANALYSIS

A multivariate method for aligning Raman spectra that suffer from spec tral shifts resultant from diode laser mode-hopping is presented. This alignment method permits accurate alignment without necessitating a c onsistent reference peak while avoiding the uncertainties of estimatin g the maxima of broad or noisy peaks. This method differs from multiva riate standardization methods in that the training set needs to be mea sured only once. The spectra are not compared to the spectra of a sepa rate instrument. It is shown that the alignment enhances the performan ce of Raman spectroscopy for quantitative and qualitative applications . This evidence is supported by Monte Carlo simulations, quantitation of a mixture of aromatics by Raman spectroscopy, and imaging of a poly mer surface by a Raman microscope.