Total Luminescence

In a given reaction, when correction is made for the spontaneous oxidation of luciferin, the total light is proportional to the amount of luciferin initially present, and is practically independent of the amount of luciferase in dilutions between 1 and 125 (3). Per unit of luciferin the total light is influenced by both the buffer system and the pH it is less in phthalate than phosphate buffer, and less at pH 6.8 and 7.8 than at pH 6.0. It decreases from 2 to 3.5% per degree with rise in temperature between 16 and 28 C. More extensive data are needed in order to interpret these effects. 

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Fig. 4.3.1 Effect of pH on the total light emission of phialidin (A), and the temperature stability profiles of phialidin (minute open circles) and aequorin (solid line) (B). In A, each buffer contained 0.1 M CaCl2 plus 0.1 M Tris, glycine or sodium acetate, the pH being adjusted with NaOH or HC1. In B, the photoprotein samples in 10 mM Tris-EDTA buffer solution, pH 8.0, were maintained at a test temperature for 10 min, and immediately cooled in an ice water bath. Then total luminescence activity was measured by injecting 1ml of 0.1 M CaCl2/Tris-HCl, pH 7.0, to 10 pd of the test solution. From Levine and Ward (1982), with permission from Elsevier.

Figure 2. Total-luminescence contour plots of an anthracene-perylene mixture prior to extraction (a) and following extraction (b) with y-cyclodextrin.

TEP TL TLC TMB TMP TMP TMPG TNS TPB TRIS TRITC TTAB UA USDA-FSIS Triethylphosphine Total luminescence Thin layer chromatography T etramethylbenzidine 2,4,6,8-Tetrathiomorpholinopyrimido [5,4-d] pyrimidine Trimethylphosphine S S -Trimethoxyphenylglyoxal Potassium 2-p-toluidinylnaphthalene-6-sulfonate Tetradecylpyridine bromide Tris (hydroxymethyl) aminomethane Tetramethylrhodamine isothiocyanate Tetradecyltrimethyl ammonium bromide Uric acid U.S. Department of Agriculture-Food Safety and Inspection Service... 

The value of the phosphorescence quantum yield can be determined by measuring the total luminescence spectrum under steady irradiation. If the fluorescence quantum yield is known then the phosphorescence quantum yield may be found by comparing the relative areas under the two corrected spectra. 

Fig. 25. Simnltaneous recording of total luminescence and phosphorescence. (From Vo Dinh and Wild, Ref. 71)...

For operational purposes, fluorescence is understood to be short-lived and phosphorescence to be long-lived luminescence. The spectrometer described here uses only a single light chopper 9 and allows simultaneous recording of total luminescence and phosphorescence spectra (Fig. 25). 

Vo Dinh, T., Wild, U. P. High resolution luminescence spectrometer. 1 Simultaneous recording of total luminescence and phosphorescence. Appl. Opt. 12, 1286 (1973). 

Luminescence spectrophotometry consists of fluorescence, phosphorescence and low-temperature total luminescence. Fluorescence is generally measured at room temperature. Phosphorescence is generally observed at liquid nitrogen temperature (77K) with the aid of a chopper to interrupt the exciting radiation. Total luminescence is the combined fluorescence and phosphorescence obtained at low temperature (77K). Luminescence spectrophotometry is generally much more sensitive and specific than absorption spectrophotometry. 

Latz and Madsen (33) investigated the total luminescence of coumarin derivatives isolated from expressed lime oil. They suggested the possibility of using excitation and emission spectra to detect the presence of chalcones and methyl salicylates added to adulterate expressed oils. 

Since the CL emission decreases upon treatment of polypropylene with peroxide-destroying agents, such as sulphur dioxide, it was concluded that the emission originated from hydroperoxides present in the material [28]. The area under the CL emission peak is denoted total luminescence intensity (TLI) and has been found to be proportional to the hydroperoxide concentration in the early stages of the oxidation of polypropylene [28]. 

Mobed, J. J., S. L. Hemmingsen, J. L. Autry, and L. B. McGowan. 1996. Fluorescence characterization of IHSS humic substances total luminescence spectra with absorbance correction. Environmental Science Technology 30 3061—3065. 

Bidimensional fluorescence spectra are commonly obtained in the three modes of emission, excitation, and synchronous-scan excitation, whereas tridimensional fluorescence (or total luminescence) spectra are obtained in the form of excitation-emission matrix (EEM) plots by measuring the fluorescence intensity emitted as a function of the wavelength over a range of excitation wavelengths. This technique allows to obtain more detailed information than that obtained by using conventional monodimensional fluorescence (Mobed et al., 1996). Fluorescence spectroscopy has provided valuable information on the molecular structure, functionalities, conformation, and intramolecular and intermolecular interactions of HS from organic amendments and unamended and amended soils (Senesi et al., 1990,1996, 2007 Mobed et al., 1996 Chen et al., 2003 Senesi and Plaza, 2007). 

Figure 10.10. Total luminescence spectrum of a water sample (brown water H019).

FIGURE 5 33 CpL (upp curve) total luminescence (lower curve) for a 0.05 M aqueous solution of Tb(III) with the ligand shown. CPL is observed from this racemic mixture following circularly polarized laser excitation at 488 nm 6... 

Pressure effects on the energy transfer between f elements of the same kind were studied by Merkle et al. (1981) for the case of Nd3+-Nd3+ pairs in Ndx Y xP50i4 (x = 1,0.1). This material was studied in detail because of its potential use as a stoichiometric laser material. An outstanding property is a very weak concentration quenching of the luminescence. The total luminescence decay rate of the 4F3/2 multiplet in Ndx Y xP50i4 (x = 1,0.1) underpressure is shown in fig. 17. Obviously the stoichiometric compound shows a much larger increase of the decay rate than the doped compound. 

Fig. 17. Total luminescence decay rate of 4F3/ i in NdxYi xP50i4 for a = 0.1 and 1.0, as afunction of pressure (from Mcrklc et al. (1981)).

D spectral contours, such as obtained in "total-luminescence spectroscopy" (excitation vs. emission)(8-10) can be simultaneously acquired, and actually monitored in real-time, by the OMA. 

Very recently the research groups of Professor F. S. Richardson at the University of Virginia, and Dr. H. P. J. M. Dekkers of the University of Leiden have built instruments capable of measuring the time dependence of the CPL intensity [14-24], As is evident from eqs. (8) and (9), for the simple system described in the previous section, in which we assumed no competing excited state processes, the time dependence of the CPL intensity would be exactly equal to that measured for the total luminescence intensity. Time-resolved CPL (TRCPL) is, therefore, an experiment suited for the study of excited state processes that result in optical activity changes. We will summarize here the theoretical formalism for two such processes, namely, excited state racemization, and excited state enantioselective quenching. 

If only one emitting species contributed to the observed luminescence from this sample, then the lineshape of the total luminescence (TL) and the CPL should be independent of excitation polarization. That this is not the case for this system is most evident in examination of the CPL in the two figures. Obviously, in this system, preparation of solutions with a 1 2 1.5 ratio of metal DPA L-Mal do not yield complexes solely with this stoichiometry. 

Sometimes the fluorescence and phosphorescence spectra of a compound in solution overlap. They may be separated as follows. If a suitable triplet energy acceptor is added, this will quench the phosphorescence, leaving the fluorescence unaffected, while a suitable triplet donor will sensitize the phosphorescence in the absence of any fluorescence. Back-strom and Sandros have analyzed the total luminescence spectra of biacetyl, benzil, and anisil in this way, using pyrene as the triplet acceptor and benzophenone as triplet donor.3... 

The total luminescence intensity is the product of the number of excited electron-hole pairs and the recombination rate, N /x. If tIl is the luminescence quantum efficiency and G is the excitation intensity, then by definition, t i, G is the luminescence intensity. is the density of states which are occupied by electron-hole pairs. Since cannot be greater than the available density of states at the emission energy, then it follows from Eq. (8.30) that... 

Marhaba et al. (2000) have measured the total luminescence spectra of the six fractions of DOM that can be obtained using the fractionation procedure of Leenheer and Huffman (1976), which is described in Section 5.10.4.2.1. 

Fluorescence-detected circular dichroism (FDCD) is a chiroptical technique in which the spectrum is obtained by measuring the difference in total luminescence obtained after the sample is excited by left- and right-circularly polarized light. For the FDCD spectrum of a given molecular species to match its CD spectrum, the luminescence excitation spectrum must be identical to the absorption spectrum. 

Molecular fluorescence spectroscopy is a commonly employed analytical method that is sensitive to certain chemical properties of FA (9-13). Fulvic acid s molecular fluorescence is principally due to conjugated unsaturated segments and aromatic moieties present in the macromolecule (14). Several types of fluorescence spectra can be measured, including an excitation emission matrix or total luminescence spectrum, constant offset synchronous fluorescence, excitation spectra, and emission spectra, furnishing the researcher with useful data. The ability to resolve and select multiple fluorescent species makes these approaches extremely useful for studying FA relative to its chemical reactivity. 

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