Fluorometric

One otlier common source of nonlinear response, singlet-triplet annihilation, is often tire reason for a discrepancy between fluorometric and absorjDtion kinetic measurements [27, 28 and 29]. 

Selected Chelating Agents for the Fluorometric Analysis of Inorganic Metal Ions... 

Riboflavin can be assayed by chemical, en2ymatic, and microbiological methods. The most commonly used chemical method is fluorometry, which involves the measurement of intense yeUow-green fluorescence with a maximum at 565 nm in neutral aqueous solutions. The fluorometric deterrninations of flavins can be carried out by measuring the intensity of either the natural fluorescence of flavins or the fluorescence of lumiflavin formed by the irradiation of flavin in alkaline solution (68). The later development of a laser—fluorescence technique has extended the limits of detection for riboflavin by two orders of magnitude (69,70). 

Spectrophotometric and fluorometric reagents, once used extensively for deterrnination of beryUium (26,27), are seldom employed. Reviews of beryUium analysis are avaUable (15—17,24—30). 

En2ymatic methods have been described (34) as well as gc, Ic, radiochemical, and fluorometric procedures for ch oline analysis (32). 

In the search for new fluorometric reagents for trace metal determinations, ferroin-type compounds, namely 2-(2-pyridyl)-2//- and 2-(3-isoquinolyl)-3//-imidazo[4,5-/i]quinolines, and their silver, lead, and zinc chelates were tested for luminiscence in aqueous ethanol solutions at various pH values (80TAL1021). 

F D Snell, Photometric and Fluorometric Methods of Analysis, Parts 1/2, Metals Part 3, Non-metals, Wiley, New York, 1978-1981... 

Measured end points are photosynthesis as the incorporation of radiolabelled H C03 ( C) and bacterial activity as the incorporation of radiolabelled thymidine (thym) fluorometric measurements basal fluorescence (Fo) and photon yield (Y) chlorophyll-a concentration (chl-a) species composition (spp) and the biovolume of algae obtained after algal counting (biovolume)... 

Hence, pseudosimultaneous spectroscopic and flow-cytometric measurements suggest that actin polymerization may be functionally related to aggregation, possibly by reorganization of adhesive molecules on the cell surface. Simultaneous spectroscopic and fluorometric measurements suggest that the signal Ca may be related to oxidant production and degranulation. 

Reagents. Perylene was obtained from Sigma Chemical Company (St. Louis, Missouri). All other PAHs were supplied by Aldrich Chemical Company (Milwaukee, Wisconsin) and were reported to contain less that 3% impurities. All PAHs were used without further purification. Isopropyl ether (99%) for extraction work was also purchased from Aldrich. Hydroquinone, a fluorescent stabilizer present in the ether, was removed prior to solution preparation by rotary evaporation. Fluorometric-grade 1-butanol was supplied by Fisher Scientific Company (Fair Lawn, New Jersey). All solutions for extractions of PAHs were prepared by evaporating portions of a stock cyclohexane solution and diluting to the appropriate volume with isopropyl ether. Fluorescence measurements were performed on 1 10 dilutions of the stock and final organic phase solutions. The effect of dissolved CDx on the fluorescence intensity of the organic phase PAH was minimized by dilution with isopropyl ether. 

Martin EA. 1972. [Fluorometric determination of some pesticides]. Can J Pharmacol Sci 7 21-22. (French)... 

Vol. 109. Fluorometric Analysis in Biomedical Chemistry Trends and Techniques Including HPLC Applications. By Norio Ichinose, George Schwedt, Frank Michael Schnepel, and Kyoko Adochi... 

Assays of ciguatoxin. Determination of ciguatoxin levels in fish was carried out in many laboratories by mouse assays. Enzyme immunoassay to screen inedible fish has been proposed by Hokama (9). No specific chemical assay has been developed, as information on functional groups suitable for fluorescence labeling is not available. Analyses conducted in the authors laboratory on remnant fish retrieved from patients meals indicated that ciguatoxin content as low level as 1 ppb could cause intoxication in adults. An extremely high sensitivity and a sophisticated pretreatment method will be required for designing a fluorometric determination method for the toxin. 

Figure 6. Fluorometric HPLC of diarrhetic shellfish toxins A, AM (9-anthrylmethyl) esters of constituents which have a carboxylic acid column, Develosil ODS (Nomura Chem.) solvents, CH3CN-CH3OH-H2O (8 1 1) monitor ex. 365, em. 412 nm and B, AN (anthroyl) esters of PTXl and PTX4 column and solvents were the same as those in A monitor x. 365, em. 465.

If the fluorometric procedure is used, with protein precipitation, then bilirubin will not interfere with the hexokinase procedure. Even if protein precipitation is not resorted to, the interference from bilirubin does not become significant until one is dealing with an infant in severe jaundice. This can be seen in Table III. 

If the fluorometric method is used after protein precipitation then the glucose can be readily assayed on 1 pi of plasma with the hexokinase procedure. 

Effect of bilirubin on the glucose fluorometric hexokinase procedure with and without protein precipitation, ... 

Tomisek, A. J. and Natelson, S. Fluorometric assay of ultramicro quantities of glucose with Somogyi filtrate and hexokinase. Micro-chem. J. (1974),... 

Navas-Diaz, A. and Ramos-Peinado, M.C., Fluorometric determination of curcumin in yogurt and mustard, J. Agric. Food Chem., 40, 56, 1992. 

Because a chlorophyll molecule contains a closed circuit of ten conjugated double bounds to absorb light, spectrophotometric (UV-Vis) and fluorometric measurements are satisfactory to identify and estimate amounts of chlorophyll a and chlorophyll b, usually the only ones present in fresh plant extracts. The basis of numerous spectrophotometric determinations reported in literature is that chlorophylls strongly absorb at 500 to 700 nm in the visible region and show a large typical band around 400 nm. 

However, since fluorometric methods require sophisticated instrumentation, their applicabihty is limited because of cost. In conclusion, spectroscopic methods usually enable crude estimates of chlorophylls in an extract, but in most cases accurate and detailed analysis of a specific composition requires separation of the mixture into individual compounds using methods such as HPLC. 

---