Fluorometric methods

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

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. 

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. 

Automated colorimetric and fluorometric methods for aldehydes were proposed by Afghan et al. [134], The colorimetric method used chromatotropic acid, while the fluorometric method was based on the reaction between formaldehyde, 2,4-pentadione, and ammonia. The sensitivities of these methods were about the same as that of the Kamata method they could be employed usefully in fresh water, but were marginal for seawater. A more sensitive version of the fluorometric method for formaldehyde was developed by Zika [ 135] using the reaction as described by Belman [136]. This version had a sensitivity of 1 x 10 7 M in sea water. 

As a general rule, fluorometric methods are considerably more sensitive than spectrophotometric methods, although standardisation is more difficult. Direct fluorometric procedures for lignin and lignin sulfonates have been described [441-443]. 

For a rough estimation of the relative amounts of humic and fulvic acids, the fluorometric method has much to recommend it, not the least being its simplicity. Also, the ability of the method to measure short-range variability might be quite valuable. It is not possible to be certain of the value of any more detailed or more exact information until a great deal more is known about the nature of the compounds in each of these fractions. 

Although the equations are complex, in most cases the minor terms are such that many can he neglected. Further simplification is often possible when one considers that, in most offshore seawater samples, the only primary pigments found are chlorophylls a and c, along with phaeophytin a. Chlorophyll b and phaeophytins b and c are either absent or present in minor amounts. Phaeophorbides are also commonly found. However, these would probably have very similar fluorometric properties to the phaeophytins, and hence could not be separately determined by any fluorometric method. 

Spectrophotometric determination with 4-hexylresorcinol and a fluorometric method with m-aminophenol are the most commonly used procedures for the determination of acrolein. However, gas chromatography and high-performance liquid chromatography procedures are also used (USEPA 1980 Kissel etal. 1981 Nishikawa and Hayakawa 1986). Acrolein concentrations in rainwater between 4 and 200 pg/L can be measured rapidly (less than 80 min) without interference from related compounds the method involves acrolein bromination and analysis by gas chromatography with electron capture detection (Nishikawa and Hayakawa 1986). Kissel etal. (1981) emphasize that water samples from potential acrolein treatment systems require the use of water from that system in preparing blanks, controls, and standards and that acrolein measurements should be made at the anticipated use concentrations. 

Determination of 58.3 jg of boron by the spectrophotometric method and 2.38pg of boron by the fluorometric method... 

Tolerated limit (M) as the concentration level at which the interfered causes an error of not more than 2% (spectrophotometric method) or 3% (fluorometric method)... 

Electrochemical and fluorometric methods of determining alkyl tin compounds have been discussed [104, 105]. 

At the present time, two methods are in common use for the determination of time-resolved anisotropy parameters—the single-photon counting or pulse method 55-56 and the frequency-domain or phase fluorometric methods. 57 59) These are described elsewhere in this series. Recently, both of these techniques have undergone considerable development, and there are a number of commercially available instruments which include analysis software. The question of which technique would be better for the study of membranes is therefore difficult to answer. Certainly, however, the multifrequency phase instruments are now fully comparable with the time-domain instruments, a situation which was not the case only a few years ago. Time-resolved measurements are generally rather more difficult to perform and may take considerably longer than the steady-state anisotropy measurements, and this should be borne in mind when samples are unstable or if information of kinetics is required. It is therefore important to evaluate the need to take such measurements in studies of membranes. Steady-state instruments are of course much less expensive, and considerable information can be extracted, although polarization optics are not usually supplied as standard. 

Rogers and Staruszkiewicz (1997). Collaborative study-GLC determination of cada-verine and putrescine in seafood fluorometric method for histamine in tuna and mahimahi, J. AO AC, 80, 591. 

Argauer, R. J. and M. Gilliam. 1974. A fluorometric method for determining oxytetracycline in treated colonies of the honey bee. Apis mellifera. J. Invertebr. Pathol. 23 51-4. 

Since the PSP toxins lack native fluorescence, useful UV absorption or adequate volatility, more traditional analytical procedures such as gas chromatography or spectrometry have proven ineffective in assaying for the toxins. A number of chemical assays for the toxins have been developed though with the fluorometric method of Bates and Rapoport (3 ) proving to be the most useful to date. This assay is based on oxidation of the PSP toxins under alkaline conditions to fluorescent derivatives. The assay is highly sensitive, fairly specific for the PSP toxins and was incorporated into a detection method in the column chromatographic separation of the toxins described by Buckley et al (4 ). 

Following the incorporation of a number of modifications, the fluorometric method was utilized in a post column reaction system (PCRS) with separation of the toxins by high pressure liquid chromatography (HPLC) (, ). While this system proved quite useful... 

The inability of the fluorometric method to directly assess the presence of the neo-STX group (neo-STX, GTXl, and GTX4), due to the presence of an OH group at position presents problems in... 

The administration of spironolactone (Aldactone) interferes in the determination of 11-hydroxy corticosteroid by methods that depend on formation of fluorescence in strong sulfuric acid (W15). In 5 patients, the administration of the drug produced as much as a 5-fold increase in the apparent plasma cortisol levels. Aspirin interferes in the determinations of homovanillic acid (HVA) by a fluorometric method. The HVA fluorophore occurs at 320 nm and 420 nm, and acetylsalicylic acid produces fluorescence at 305 to 405 nm (H12). 

Fluorometric methods have been developed for determining the concentrations of more than 50 elements in the periodic table. These methods depend on the measurement of changes in the fluorescence intensity of a fluorescent dye on interaction with the species to be analysed. The concentration of the substance being analysed is proportional to the fluorescence intensity, determined from calibration curves. The interactions can take the form of ionic associates between a dye cation and a metal complex anion, e.g. AgBrj with a rhodamine cation, or alternatively with a fluorescent dye anion, e.g. fluorescein and a complex cation. In another method, the changes... 

A fluorometric method was developed for determination of atmospheric H2O2 simultaneously with other species present at ppbv or lower levels, avoiding chromatographic separation. H2O2 is selectively collected by diffusion through a Nafion membrane, and is carried by a water stream into a reactor where it oxidizes thiamine hydrochloride (117) to a fluorescent ionic form of thiochrome (118), catalyzed by bovine hematin (75b) in alkaline solution, as shown in equation 40. The end solution containing 118 is passed through... 

Lazrus, A. L., G. L. Kok, S. N. Gitlin, and J. A. Lind, Automated Fluorometric Method for Hydrogen Peroxide in Atmospheric Precipitation, Anal. Chem., 57, 9f7-922 (f985). 

Phosphorimetric methods have been used to determine such substances as nucleic acids, amino acids, and enzymes. However, this is not a widely used method since it cannot be run at room temperature. Measurements are usually performed with liquid nitrogen to prevent degradation due to collision deactivation. Fluorometric methods are used to determine both inorganic and organic species. Instruments used for measuring fluorescence and phosphorescence are fluorometers and spectrofluorometers, respectively. These instruments are similar to ultraviolet and visible spectrometers,... 

Although tetracyclines possess the inherent ability to fluoresce, few methods exploiting this property have been reported (300, 306, 309). Instead, fluorometric methods based on the reaction of tetracyclines with suitable derivatizing agents have been developed. The use, for example, of zirconyl chloride as a fluorescence label in the postcolumn derivation of tetracyclines, has allowed highly selective and sensitive detection of these antibiotics in animal tissues (294, 295). 

Tsutsui, T., Li-Chan, E and Nakai, S. 1986. A simple fluorometric method for fat-binding capacity as an index of hydrophobicity of proteins. J. Food Sci. 51 1268-1272. 

A recent interlaboratory comparison of HPLC and fluorometric methods reported good agreement between laboratories for vitamin C in green beans (42). 

This is one vitamin that most laboratories can measure. There are a number of old-fashioned approaches that use 2,6-dichloroindophenol in a titrimetric method such as AOAC 985.33. This works well in some systems but can give rise to false positive results if there are other reducing substances present. It will not detect dehydroascorbic acid (DHA) and so it may well underestimate the actual vitamin C activity if a product contains a significant level of DHA. However, even with for these shortcomings, it is often used as a quick and rough method. In the AOAC there is also a fluorometric method (AOAC 984.26) where ascorbic acid is oxidised to DHA and this is reacted with o-phenylenediamine to give a fluorometric compound which can be detected. This is a robust method that has general applicability. 

Land, D. B., and S. M. Edmonds A Fluorometric Method for Determining Trace Quantities of Phosphate. Mikrochim. Acta 1966, 1013. 

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