A shifted‐excitation Raman difference spectroscopy (SERDS) evaluation strategy for the efficient isolation of Raman spectra from extreme fluorescence interference

Abstract

A biochemical characterization of pathologies in biological tissue can be provided by Raman spectroscopy. Often, the raw spectrum is severely affected by fluorescence interference. We report and compare various spectra-processing approaches required for the purification of Raman spectra from heavily fluorescence-interfered raw spectra according to the shifted-excitation Raman difference spectroscopy method. These approaches cover the entire spectra-processing chain from the raw spectra to the purified Raman spectra. In detail, we compared (1) area normalization versus z-score normalization, (2) direct reconstruction of the difference spectra versus reconstruction of zero-centered difference spectra and (3) collective baseline correction of the reconstructed spectra versus piecewise baseline correction of the reconstructed spectra and, finally, (4) analyzed the influence of the shift of the excitation wavelength on the quality of the reconstructed spectra. Statistical analysis of the spectra showed that -in our experiments -the best results were obtained for the z-score normalization before subtraction of the normalized spectra, followed by zero-centering of the difference spectra before reconstruction and a piecewise baseline correction of the pure Raman spectra. With our equipment, a wavelength shift from 784 to 785 nm provided reconstructed spectra of best quality. The analyzed specimens were different tissue types of pigs, tissue from the oral cavity of humans and a model solution of dye dissolved in ethanol.

A portable shifted excitation Raman difference spectroscopy system: device and field demonstration

“…Shifted excitation Raman difference spectroscopy (SERDS) and related methods have been demonstrated as powerful spectroscopic tools separating the Raman signals from background interferences . For SERDS, a laser light source with two slightly shifted excitation lines is necessary, generating two slightly shifted Raman spectra.…”

Recent advances in linear and non‐linear Raman spectroscopy. Part XI

“…With their equipment, a wavelength shift from 784 to 785 nm provided reconstructed spectra of the best quality. The analyzed specimens were different tissue types of pigs, tissue from the oral cavity of humans, and a model solution of dye dissolved in ethanol . Gilg et al studied the determination of titanium content in pyrope by Raman spectroscopy.…”

Vector casting for noise reduction

“…The origin of small SNRs can be manifold. Small available or realizable excitation powers in combination with small interaction probabilities (cross sections) between the excitation and the matter under investigation often result in small SNRs . Also, a less efficient signal detection or short acceptable signal integration time can result in small SNRs .…”