Automatic standardization method for Raman spectrometers with applications to pharmaceuticals

An effective and practical method, based on automatic peak detection, Lorentzian fitting, and polynomial fitting, is developed for aligning spectra, which can significantly reduce or eliminate systematic differences between Raman spectrometers. In this work, Lorentzian fitting of the experimental spectra is performed to precisely locate the peak positions. Then the standardization procedure is illustrated on the spectra of a chemical standard measured on primary and secondary instruments, and the spectra can be successfully aligned to each other after shift correction. It is shown that the similarity of pharmaceutical spectra acquired on three Raman spectrometers is then considerably improved after removal of the Raman shift difference. The result shows that the similarity of the spectra between primary and secondary spectrometers increases dramatically from about 0.8 to 0.95 after spectra standardization. This means that the proposed standardization method can effectively reduce or eliminate systematical errors and enhance spectral compatibility across different instruments. Copyright (c) 2014 John Wiley & Sons, Ltd.