Raman spectroscopy fluorescence background

The above formula does not take into account the fluorescence background, which is a common problem for Raman spectroscopy. This background reduces the SNR for Raman measurements (Yakovlev 2007) by a factor of... 

Beside the identification of single bacterial cell or spores by means of Raman spectroscopy, the localization of these cells inside partly complex matrices has to be performed. One approach is the combination of Raman spectroscopy, fluorescence spectroscopy and digital imaging techniques. This method was applied to detect traces of endospores and other biothreat organisms even in the presence of complex environmental matrices like bioaeroso-lic background, nasal mucin [67], or tap water [68], Another fully automated device was built to analyze bioaerosols in clean room environments, where prior to the Raman identification method a particle preselection took place [69]. 

Fluorescence Interference. The historical drawback to widespread use of Raman spectroscopy has been the strong fluorescence background exhibited by many materials, even those which are nominally nonfluorescent. This fluorescence often arises from an impurity in the sample, but may be intrinsic to the material being studied. Several methods have proved useflil in reducing this background. One of the simplest is sample purification. 

Principles and Characteristics The prospects of Raman analysis for structural information depend upon many factors, including sample scattering strength, concentration, stability, fluorescence and background scattering/fluorescence from the TLC substrate. Conventional dispersive Raman spectroscopy has been considered as a tool for in situ analysis of TLC spots, since most adsorbents give weak Raman spectra and minimal interference with the spectra of the adsorbed species. Usually both silica and cellulose plates yield good-quality conventional Raman spectra, as opposed to polyamide plates. Detection limits for TLC fractions... 

The limit of detection by Raman spectroscopy was 3-5 weight % for the oxime ester and methacrylonitrile for these samples. The shorter time required to reduce background fluorescence in those samples filtered through activated charcoal indicates that more careful sample preparation and purification would lower this limit. 

At present, Raman spectroscopy for ocean measurements is limited by the weakness of the phenomenon and the type of equipment required. Seawater exhibits background fluorescence due to dissolved organic solutes, and thus sensitivity is further compromised. An especially important interfcranl is chlorophyll, which fluoresces upon excitation with argon lasers. 

Biopharmaceutics is a fast growing area with many new opportunities for the pharmaceutical industry. Raman process monitoring has some great potential in this field due to its compatibility with water, in contrast to, e.g. IR or THz spectroscopy, although very little has been demonstrated so far. There are also challenges to be considered such as significant fluorescence background... 

Li etal. discuss the use of on-line Raman spectroscopy to dynamically model the synthesis of aspirin, one of the most documented and well-understood reactions in organic chemistry. That makes it an excellent choice for building confidence in the sampling interface, Raman instrumentation, and analysis procedures. The researchers used wavelets during analysis to remove fluorescent backgrounds in the spectra and modeled the concentrations with multiple linear regression.53... 

In many spectroscopic techniques, it is not unusual to encounter baseline offsets from spectrum to spectrum. If present, these kinds of effects can have a profound effect on a PCA model by causing extra factors to appear. In some cases, the baseline effect may consist of a simple offset however, it is not uncommon to encounter other kinds of baselines with a structure such as a gentle upward or downward sloping line caused by instrument drift, or even a broad curved shape. For example, in Raman emission spectroscopy a small amount of fluorescence background signals can sometimes appear as broad, weak curves. 

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