Fluorescence variable

Boehme, J., and Wells, M. (2006). Fluorescence variability of marine and terrestrial colloids Examining size fractions of chromophoric dissolved organic matter in the Damariscotta River estuary. Mar. Chem. 101, 95-103. 

Table 32.1 Orthogonality (sinO) calculated between fluorescence variables (Ex, Em,X) ofeach pairoftwodififerentfluorescentdyes.

Boehme, J., Coble, P, Conmy, R., and Stovall-Leonard, A. (2004). Examining CDOM fluorescence variability using principal component analysis Seasonal and regional modeling of three-dimensional fluorescence in the Gulf of Mexico. Mar. Chem., 89, 3-14. 

Note that in liquid phase chromatography there are no detectors that are both sensitive and universal, that is, which respond linearly to solute concentration regardless of its chemical nature. In fact, the refractometer detects all solutes but it is not very sensitive its response depends evidently on the difference in refractive indices between solvent and solute whereas absorption and UV fluorescence methods respond only to aromatics, an advantage in numerous applications. Unfortunately, their coefficient of response (in ultraviolet, absorptivity is the term used) is highly variable among individual components. 

The different techniques of NDT were applied to evaluate the method allowing to give an optimal spectrum so that the interpretation can be done easily. In addition, and for the purpose of the defects quantification, we have done an optimization on the magnetic powders, colored and fluorescent, by applying magnetic powders of variable dimensions. This will enable us to estimate defects with a high precision. 

Measuring process parameters on full-scale plants is notoriously difficult, but is needea for control. Usually few of the important variables are accessible to measurement. Recycle of material makes it difficult to isolate the effects of changes to individual process units in the circuit. Newer plants have more instrumentation, including on-line viscosimeters [Kawatra and Eisele, International ]. Mineral Processing, 22, 251-259 (1988)], mineral composition by on-line X-ray fluorescence, belt feeder weighers, etc., but the information is always incomplete. Therefore it is helpful to have models to predict quantities that cannot be measured while measuring those that can. 

Even the fact that some species do not fluoresce may be used as a selectivity tool. Computers and modem electronics have made multidimensional measurements possible on a hitherto unprecedented scale and this approach has been one of the most effective ways to achieve high selectivity in luminescence measurements. Many ingenious techniques have recently become available for utilizing the multiple luminescence variables and these have made luminescence measurements a routine and valuable tool in almost all areas of experimental science. 

McDermott F, Mattey DP, Hawkesworth CJ (2001) Centennial-scale Holocene climate variability revealed by a high-resolntion speleotherm record from SW Ireland. Science 294 1328-1331 McGarry SF, Baker A (2000) Organic acid fluorescence applications to speleothem paleoenvironmental reconstraction. Qnat Sci Rev 19 1087-1101... 

The variable delay can be as simple as an RC network. Often the variable delay line is calibrated directly in terms of lifetime units (nanoseconds). When the reference and comparison signals are in phase the fluorescence lifetimes can simply be read off the calibrated variable delay. 

The same considerations will apply to other nonspecific methods of detection, such as fluorescence or UV absorbance determinations. Particularly with these methods, it must be appreciated that many of the cells used to form mono-layers secrete a variety of products such as lipids and proteins into both the donor and receiver compartments. These substances can result in a variable background in solutions and may interfere with solute quantitation. Even if a chromatographic method is used with fluorescence or UV detection, these products can still interfere with the separation unless specifically accounted for. 

---