INDEX fluorescent

Which of the four HPLC detectors (UV absorbance, refractive index, fluorescence, or conductivity)... 

Other types of detection include refractive index, fluorescence, or mass selective detectors. The use of other types of detectors, such as those based on fluorescence, may be used for assaying compounds that can be specifically detected at low concentrations in the present of nonfluorescent species. However, as few compounds are naturally fluorescent, they require chemical modification, assuming they have a suitable reactive group, to give a fluorescent derivative. 

Several approaches are used to analyze and/or fractionate the rotor effluent. The simplest is to split the gradient into fractions according to volume. Alternatively, the effluent may be routed through one or more in-line flow cells to monitor a selected gradient property, e.g., density, absorbance, refractive index, fluorescence, etc. Automated fractionators that switch collection vessels according to effluent volume or to feedback from an in-line detector are available. 

LC provides good reproducibility and high-quality results the cost is reasonable for routine applications and it is fairly easy to operate the equipment. UV-visible detectors are most commonly used for routine impurity determinations by LC. Other detectors that are useful for the identification of impurities or for specialized purposes are refractive index, fluorescence, electrothermal detectors, polarimeters, Fourier transform infrared spectrometers, and mass spectrometers. 

The relatively simple study of fluorescence and phosphorescence (based on the action of colour centres) has nowadays extended to nonlinear optical crystals, in which the refractive index is sensitive to the light intensity or (in the photorefractive variety (Agullo-Lopez 1994) also to its spatial variation) a range of crystals, the stereotype of which is lithium niobate, is now used. 

The procedure utilises eriochrome blue black RC (also called pontachrome blue black R Colour Index No. 15705) at a pH of 4,8 in a buffer solution. Beryllium gives no fluorescence and does not interfere iron, chromium, copper, nickel, and cobalt mask the fluorescence fluoride must be removed if present. The method may be adapted for the determination of aluminium in steel. 

Detection of the these types of compounds are sometimes difficult as many components of cosmetic products are aliphatic, do not possess a UV chromophore and are not easily reacted to give fluorescent derivatives. Providing the concentration of the component of interest is sufficiently high, then a refractive index detector is often used. If... 

The choice of detector is often crucial to the success of a particular HPLC method. A number are in routine use, including the UV, fluorescence, electrochemical, conductivity and refractive index detectors, and each has particular advantages and disadvantages, details of which can be found elsewhere [2-4],... 

Griffiths, H.R, Lunec, J. and Blake, D.R. (1992). Oxygen radical-induced fluorescence in proteins identification of the fluorescent tryptophan metabolite N formyl kynurenine as a biological index of radical damage. Amino Acids 3, 183-194. 

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