Degradation fluorescence spectroscopy

Fourier transform infrared (FTIR) spectroscopy, 13C nuclear magnetic resonance (NMR) spectroscopy, ultraviolet-visible (UV-VIS) and fluorescence spectroscopy can be integrated with chromatographic techniques especially in the study of ageing and degradation of terpenic materials. They can be used to study the transformation, depletion or formation of specific functional groups in the course of ageing. 

Investigation turned then to chemical and spectroscopic means to obtain the needed mechanistic understanding. Stephenson et al. [17] looked at gas evolution versus exposure, while Pacifici and Straley [18] used UV fluorescence spectroscopy to identify a photo-oxidation product which was later isolated by Valk et al. [19]. In addition, Valk and co-workers [19-21] isolated a number of additional photolysis products by a combination of hydrolysis and chromatography, Marcotte et al. [22] used ESR to look at radicals generated during degradation, and Day and Wiles [23-26] carried out extensive IR and fluorescence spectroscopic investigations on this subject. 

Fluorescence spectroscopy and mass spectrometry have suggested that a ternary complex of iron-cyclodextrin-pollutant exists in solution. Such a complex is believed to play a key role in increasing pollutant degradation rates. Studies using added scavengers also support this theory [38]. A schematic illustration of such a theorized ternary complex is depicted in Figure 5. 

The study by Determan et al. [224] focuses on the effects of polymer degradation products on the primary, secondary, and tertiary structure of TT, OVA, and lysozyme after incubation for 0 or 20 days in the presence of ester (lactic acid and glycolic acid) and anhydride [sebacic acid and l,6-bis(p-carboxyphenoxy)hexane] monomers. The structure and antigenicity or enzymatic activity of each protein in the presence of each monomer was quantified. SDS-PAGE, circular dichroism, and fluorescence spectroscopy were used to assess/evaluate the primary, secondary, and tertiary structures of the proteins, respectively. ELISA was used to measure changes in the antigenicity of TT and OVA and a fluorescence-based assay was used to determine the enzymatic activity of lysozyme. TT toxoid was found to be the most stable in the presence of anhydride monomers, while OVA was most stable in the... 

Spectroscopic techniques used to monitor the extent of degradation is shown in this column. UV — ultraviolet absorption, Vis. - visible light absorption, IR - infra-red absorption, and Fluo. — fluorescence spectroscopy... 

The cross-linking reactions of tetrafunctional epoxy resins with aromatic primary diamines were investigated by spectoscopy [141]. UV-Visible and fluorescence spectroscopies of the materials, after gelation, show signiflcant amounts of amines in the finished products. The infrared spectra also show that ether formation becomes significant only late in the cure. In addition, during the cure, especially in air, some oxidations and degradations occur [141]. This results in color formation. 

Uyguner, C.S. and Bekbolet, M., Evaluation of humic acid photocatalytic degradation by UV-Vis and fluorescence spectroscopy, Catal. Today, 101,267, 2005. 

Heat degradation of oil (antioxidant effect of Nigella seed extract) Sunflower oil 3D-FF fluorescence spectroscopy ICA Decomposition of the 3D-FF fluorescence spectra and the extraction of the signals of individual fluorophores which facilitate their interpretation (monitoring the antioxidant effect of Nigella extract during heat treatment) [78]... 

Assessing the microbial bioavailability and degradation rate constants of dissolved organic matter by fluorescence spectroscopy in the coastal upwelling system of the Ria de Vigo. Mar. Chem., 119,121-129. 

In this chapter we briefly discuss the potential of the microbial food web as a source and sink for FDOM and examine how the fluorescence characteristics change as a result of microbial processing. In addition, the combined effects of microbial and photochemical degradation on FDOM characteristics are summarized. The literature on the subject is vastly expanding and it is not our aim to provide an exhaustive review but rather to highlight specific studies as examples of how fluorescence spectroscopy is being applied to studying the microbial turnover of DOM in natural aquatic enviromnents. 

Stabilisers are usually determined by a time-consuming extraction from the polymer, followed by an IR or UV spectrophotometric measurement on the extract. Most stabilisers are complex aromatic compounds which exhibit intense UV absorption and therefore should show luminescence in many cases. The fluorescence emission spectra of Irgafos 168 and its phosphate degradation product, recorded in hexane at an excitation wavelength of 270 nm, are not spectrally distinct. However, the fluorescence quantum yield of the phosphate greatly exceeds that of the phosphite and this difference may enable quantitation of the phosphate concentration [150]. The application of emission spectroscopy to additive analysis was illustrated for Nonox Cl (/V./V -di-/i-naphthyl-p-phcnylene-diamine) [149] with fluorescence ex/em peaks at 392/490 nm and phosphorescence ex/em at 382/516 nm. Parker and Barnes [151] have reported the use of fluorescence for the determination of V-phenyl-l-naphthylamine and N-phenyl-2-naphthylamine in extracted vulcanised rubber. While pine tar and other additives in the rubber seriously interfered with the absorption spectrophotometric method this was not the case with the fluoromet-ric method. 

A major consequence of using regulatory limits based on degradant formation, rather than absolute change of the API level in the drug product, is that it necessitates the application and routine use of very sensitive analytical techniques [ 10]. In addition, the need to resolve both structurally similar, as well as structurally diverse degradants of the API, mandates the use of analytical separation techniques, for example, HPLC, CE, often coupled with highly sensitive detection modes, for example, ultraviolet (UV) spectroscopy, fluorescence (F) spectroscopy, electrochemical detection (EC), mass spectroscopy (MS), tandem mass spectroscopy (MS-MS) and so forth. 

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