Spectroscopic chemiluminescence spectroscopy

Depending on the type of reaction and analytes to be investigated, different optical spectroscopic methods are available [7]. Typically UV-Vis, near-infrared (NIR), mid-infrared (MIR) and Raman spectroscopy are the most popular in process analysis (see Table 6.1) [8]. Other, emerging in-line methods such as fluorescence and chemiluminescence spectroscopy are still of minor importance in process technologies and will be not discussed here (for additional information, see [9]). 

Luminescence is a well-established class of analytical spectroscopic techniques where a species emits light after excitation. Emission is an elecnonic nansition from an excited state as opposed to the ground state as is the case in most other spectroscopies. Photoluminescence, or light-induced fluorescence (LIE), is the most common route to induce emission where sufficient incident photons of a particular energy excite the target species via absorption. Although less common, nomadiative excitation can also occur via a chemical reaction termed chemiluminescence. Unless otherwise stated, the terms luminescence and fluorescence within this review infers excitation by light induction. 

Chemiluminescence and Bioluminescence Techniques Fluorescence Spectroscopy to Study Molecular Recognition Proteins in Cellular Systems, Chemical Tools to Study Spectroscopic Techniques Proteins... 

In recent years, there has been a rapid growth in the number of publications that report the use of surfactant monomers or micelles to improve the analytical perfommice of various spectroscopic (UV-visible spectrophotometry, fluorimetry, phosphorimetry, chemiluminescence and atomic spectroscopy), and electrochemical (especially amperometry) methods [1]. The unique properties of surfactants have been recognized as being very helpful to overcome many problems associated with the use of organic solvents in these methods. Surfactant-modified procedures yield sensitivity and/or selectivity improvements in determinations commonly performed in homogeneous solution, whereas certain analytic methods (such as room-temperature phosphorescence in solution) can be exclusively conducted in organized media. 

Luminescence is generally less intense than incandescence, but it often emanates from extremely small amounts of matter, which has beneficial implications for analytical science. Nevertheless, the utilization of luminescence for analysis is quite a recent innovation. The following commentary describes the fundamental spectroscopic and chemical principles underlying luminescence in relation to its application in analytical science. As other articles will deal with atomic spectroscopy, this discussion will be restricted to analytical molecular luminescence spectroscopy including fluorescence, phosphorescence, and chemiluminescence (bioluminescence being a special case of chemiluminescence). 

In a broad sense, spectroscopic methods applied in process analytics comprise widely used techniques like UVA IS, mid-IR, NIR, NMR and XRF, and less frequently used ones, such as Raman spectroscopy, fluorescence, chemiluminescence, acoustic emission and dielectric specfloscopy. Upcoming in-process analysis techniques are 2D-fluorescence, and laser absorption specfloscopy (LAS) with tuneable lasers and ppm level sensitivity. The availability of mini-spectrometers (e.g. UVA IS/NIR) is not highly relevant in plant environments where safety is of primary concern. 

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