Fluorescent indicator adsorption method

This analysis, abbreviated as FIA for Fluorescent Indicator Adsorption, is standardized as ASTM D 1319 and AFNOR M 07-024. It is limited to fractions whose final boiling points are lower than 315°C, i.e., applicable to gasolines and kerosenes. We mention it here because it is still the generally accepted method for the determination of olefins. 

Liquid chromatography (also called adsorption chromatography) has helped to characterize the group composition of crude oils and hydrocarbon products since the beginning of this century. The type and relative amount of certain hydrocarbon classes in the matrix can have a profound effect on the quality and performance of the hydrocarbon product. The fluorescent indicator adsorption (FIA) method (ASTM D-1319) has been used to measure the paraffinic, olefinic, and aromatic content of gasoline, jet fuel, and liquid products in general (Suatoni and Garber, 1975 Miller et al., 1983 Norris and Rawdon, 1984). 

In 1948, a procedure was described by A. L. Conrad and later refined by D. W. Ciidle and R. L. LeToumeau for determining olefins, aromatics, and saturates in cracked gasoline. This procedure evolved into ASTM Test Method D1319, Hydrocarbon Types in Liquid Petroleum Products by Fluorescent Indicator Adsorption, often abbreviated as "FIA. ... 

The first level of compositional information is group-type totals. ASTM Test Method D1319, Hydrocarbon Types in Liquid Petroleum Products by Fluorescent Indicator Adsorption, gives volume percent saturates, olefins, and aromatics in materials that boil below 315 C (600 F). This covers jet fuels but not all diesel fuels, most of which have an end point above 315°C. Despite this limitation, the method has been used widely for diesel fuel due to the lack of a suitable alternative. 

D1319 Test Method for Hydrocarbon Types in Liquid Petroleum Products by Fluorescent Indicator Adsorption ... 

Sensor fabrication occurs in two steps. The first step is the immobilization of GOx on the surface of the nanotube. This is accomplished by adding GOx to a solution of surfactant stabilized nanotubes and dialyzing away the surfactant. Dialysis is an ideal method for assembling enzymes on a nanotube surface, because the method allows retention of enzyme activity while simultaneously maintaining nanotube colloidal stability. The resulting GOx-S WNT solution exhibits a shift in the nanotube fluorescence indicative of the enzyme layer being less tightly packed around the nanotube than the surfactant layer. The second step is addition of ferricyanide to the GOx-SWNT solution. Adsorption of ferricyanide to the nanotube surface... 

Nonaqueous methods include the use of amine titration and adsorption of indicators for visual measurement of acid strength. This procedure allows both the determination of the total amount of acid sites and also the acid strength distribution. A disadvantage is that bulky molecules (amines and indicators) arc used and these may be excluded from entering small pores. With zeolites, the slow rate of diffusion and equilibration has to be taken into account. Spectroscopic measurement of acid strength may also be performed using amine titration and indicator adsorption. Ultraviolet or fluorescent indicators may be used. 

Titrimetric luminescence methods record changes in the indicator emission of radiation during titration. This change is noted visually or by instruments normally used in luminescence analysis. Most luminescence indicators are complex organic compounds which are classified into fluorescent and chemiluminescent, compounds according to the type of emission of radiation. As in titrimetry with adsorption of colored indicators, luminescence titration makes use of acid-base, precipitation, redox, and complexation reactions. Unlike color reactions, luminescence indicators enable the determination of ions in turbid or colored media and permit the detection limit to be lowered by a factor of nearly one thousand. In comparison with direct luminescence determination, the luminescence titrimetric method is more precise. 

In indirect methods of influx measurement, a color reaction, fluorescence reaction, enzyme reaction, or density change of the compartments indicate the translocation of the substrate. The indicator molecules are generally inside the compartments, but not in the outer medium. If the substrate enters the vesicles, it reacts with the indicator molecule, the indicator molecule changes its properties, and this change is measured. The reaction with the indicator generally happens quickly, so that with adsorption or fluorescence measurements the substrate intake or loss can be traced continuously. 

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