Fluorescence, test for

In addition, in our hands in the most sensitive fluorescence test for malonaldehyde (acidified, moist p aminobenzoic acid,PABA 26) authentic malonaldehyde from the tetraethoxypropane produces a characteristic intense yellowish-green fluorescence with excitation at 360 nm and emission at 450-460 nm. Oxidizing lipids of the type used in our system show the same fluorescence with PABA. 

The presumptive tests for LSD involve a fluorescence test and a chemical test. 3.23.1 Fluorescence Testing for LSD... 

A new cyanide dye for derivatizing thiols has been reported (65). This thiol label can be used with a visible diode laser and provide a detection limit of 8 X 10 M of the tested thiol. A highly sensitive laser-induced fluorescence detector for analysis of biogenic amines has been developed that employs a He—Cd laser (66). The amines are derivatized by naphthalenedicarboxaldehyde in the presence of cyanide ion to produce a cyanobenz[ isoindole which absorbs radiation at the output of He—Cd laser (441.6 nm). Optimization of the detection system yielded a detection limit of 2 x 10 M. 

In the known absence of bromoform, iodoform, chloral, and other halogenated methanes, the formation of phenyhsonitrile with aniline provides a simple and faidy sensitive but nonspecific test for the presence of chloroform, the carbylamine test. Phenyhsonitrile formation is the identification test given in the British Pharmacopoeia. A small quantity of resorcinol and caustic soda solution (10% concentration) added to chloroform results in the appearance of a yellowish red color, fluorescing yeUow-green. When 0.5 mL of a 5% thymol solution is boiled with a drop of chloroform and a small quantity of potassium hydroxide solution, a yellow color with a reddish sheen develops the addition of sulfuric acid causes a change to brilliant violet, which, diluted with water, finally changes to blue (33). 

A preliminary test for the biodegradability of the 3-phenyl- and 3-carbamoyl-2(lH)pyridones was conducted in a barnyard humus suspension. The analysis by HPLC showed some loss, and the fluorescent compounds seemed to be adsorbed onto the solid. The 3-carbamoyl-2(lH)pyridone (II) also hydrolyzed to 3-carboxylic acid-2(lH)pyridone both in the slurry test and in water solutions that had been left standing 1-2 weeks. In preliminary tests both the 3-phenyl- and the 3-carbamoyl-2(lH)pyridones apparently adsorbed to some extent on silica sand columns. In addition, the solubility of both 1-H compounds was somewhat low, 1.3 x 10 M for II, and 1.0 x 10 M for IV. 

Analyses for the Saxitoxins. Early methods for analysis of the saxitoxins evolved from those used for toxin isolation and purification. The principal landmarks in the development of preparative separation techniques for the saxitoxins were 1) the employment of carboxylate cation exchange resins by Schantz et al. (82) 2) the use of the polyacrylamide gel Bio-Gel P2 by Buckley and by Shimizu (5,78) and 3) the development by Buckley of an effective TLC system, including a new solvent mixture and a new visualization technique (83). The solvent mixture, designated by Buckley as "E", remains the best for general resolution of the saxitoxins. The visualization method, oxidation of the saxitoxins on silica gel TLC plates to fluorescent degradation products with hydrogen peroxide and heat, is an adaptation of the Bates and Rapoport fluorescence assay for saxitoxin in solution. Curiously, while peroxide oxidation in solution provides little or no response for the N-l-hydroxy saxitoxins, peroxide spray on TLC plates is a sensitive test for all saxitoxin derivatives with the C-12 gemdiol intact. 

By a strict definition, these electrical and electronic wastes are hazardous. Fluorescent lamps contain mercury, and almost all fluorescents fail the U.S. Environmental Protection Agency (U.S. EPA) toxicity test for hazardous wastes. Fluorescent lamp ballasts manufactured in the mid-1980s contain polychorinated biphenyls (PCBs), a carcinogen most of these ballasts are still in service. Batteries can contain any of a number of hazardous materials, including cadmium (nickel-cadmium... 

Caturla, F., Enjo, J., Bemabeu, M. C. and Le Serre, S. (2004). New fluorescent probes for testing combinatorial catalysts with phosphodiesterase and esterase activities. Tetrahedron 60, 1903-1911. 

The first intravascular sensor for simultaneous and continuous monitoring of the pH, pC>2, and pCC>2 was developed by CDI-3M Health Care (Tustin CA)14 based on a system designed and tested by Gehrich et al.15. Three optical fibres (core diameter = 125 pm) are encapsulated in a polymer enclosure, along with a thermocouple embedded for temperature monitoring (Figure 3). pH measurement is carried out by means of a fluorophore, hydroxypyrene trisulfonic acid (HTPS), covalently bonded to a matrix of cellulose, attached to the fibre tip. Both the acidic ( eXc=410 nm) and alkaline ( exc=460 nm) excitation bands of the fluorophore are used, since their emission bands are centred on the same wavelength (/-cm 520 nm). The ratio of the fluorescence intensity for the two excitations is measured, to render the sensor relatively insensitive to fluctuations of optical intensity. 

A later paper65 reported a fluorescence maximum for leucovorin at 365 nm when excited at 314 nm in a pH 7 solution the concentration was 5 x 10-5 M. Variation between these data and other values was attributed to sample impurity, pH of solution, and quenching. The authors made an attempt to correlate structure and fluorescence of reduced folates. Similarity between tested compounds and jj-aminobenzoyl-glutamate lead them to conclude that this portion of the molecule is responsible for maxima at 360-425 nm when excited at 300-320 nm. They suggested that intensity differences may arise from various substitutions on the tetra-hydropteridine moiety. 

Cross-reactive sensing arrays were developed to detect odors and vapors in an artificial nose manner. Solvatochromic dyes such as Nile Red are adsorbed on the surface or embedded into various polymeric or porous silica beads. The beads respond to analyte vapor by a change in fluorescence maxima or/and intensity due to changes of polarity inside the bead. A portable instrument and preliminary field test for the detection of petroleum products was recently described [106]. 

None of the involved species are fluorescent. Therefore, for fluorescence signaling of citrate recognition, carboxyfluorescein is first added to the medium because binding to the receptor in the absence of citrate is possible and causes deprotonation of carboxyfluorescein, which results in high fluorescence. Citrate is then added, and because it has a better affinity for the receptor than carboxyfluorescein, it replaces the latter, which emits less fluorescence in the bulk solvent as a result of protonation. Note that this molecular sensor operates in a similar fashion to antibody-based biosensors in immunoassays. It was succes-fully tested on a variety of soft drinks. 

In the past ten years, numerous applications of fluorescence methods for monitoring homogeneous and heterogeneous immunoassays have been reported. Advances in the design of fluorescent labels have prompted the development of various fluorescent immunoassay schemes such as the substrate-labeled fluorescent immunoassay and the fluorescence excitation transfer immunoassay. As sophisticated fluorescence instrumentation for lifetime measurement became available, the phase-resolved and time-resolved fluorescent immunoassays have also developed. With the current emphasis on satellite and physician s office testing, future innovations in fluorescence immunoassay development will be expected to center on the simplification of assay protocol and the development of solid-state miniaturized fluorescence readers for on-site testing. 

Figure 6. Semi quantitative evaluation of spontaneous adsorption of collagen IV conjugated with a fluorescence marker Oregon Green 488 (A) to polyethylene foils iradiated with ions (energy 30 keV, dose from lO to lO ions/cm ), and its correlation with the number of rat aortic smooth muscle cells initially adhering to the polymer on day 1 after seeding (B). Collagen was diluted in phosphate-buffered saline to the concentration of 0.02 mg/ml (10 pg/cm ) and incubated with the foils for 24 h at room temperature. Mean+SEM from 4-9 experiments. Student t-test for unpaired data [43].

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