Detection using laser-induced fluorescence

A CZE experiment was performed using an open 50-pm diameter silica capillary, 50 cm long. A 5-mM carbonate buffer at pH 10 was used, with a separation voltage of 25 kV, following a 15 s, 1-kV electrokinetic injection of an FITC-derivatized amino acid mixture. Detection using laser-induced fluorescence showed that the mixture contained three main components, with elution times of 4.5, 6.3, and 10.2 min. How would these elution times be expected to... 

We have developed a new technique of laser pyrolysis/laser fluorescence, or LP/LF (J ), designed to furnish direct measurement of rate constants of reactions involving free radicals at elevated temperatures (800-1400K). A pulsed CO2 laser is used to heat a sample containing a precursor that pyrolyzes to form radicals. These radicals are then detected using laser-induced fluorescence (LIF). The measurement of the radical removal rates in the presence of added reactant then yields the rate constant for the selected conditions of temperature (T) and pressure (P). 

TUMOUR DETECTION USING LASER-INDUCED FLUORESCENCE... 

A stereoselective determination of enantiomers of 5, its A -oxide and N-desmethyl metabolites in human urine was developed by capillary electrophoresis using laser-induced fluorescence detection and sulfonated /1-cyclodextrin in the running buffer (01JC(B)169). 

Using the same PAbs an optical biosensor system has been developed for 2,4,6-TCP [224]. The principle is the detection of laser-induced fluorescence (LIF) in single microdroplets by a homogeneous quenching fluorescence immunoassay (QFIA). The competitive immunoassay occurs in microdroplets (d=58.4 mm) produced by a piezoelectric generator system. A continuous Ar ion laser (488 nm) excites the fluorescent tracer and its fluorescence is detected by a spectrometer attached to a cooled, charge-coupled device (CCD) camera... 

Concentrations of OH and HO2 were determined, in situ, using Laser Induced Fluorescence (LIF) at low pressure, (FAGE technique). HO2 cannot be detected directly by LIF, and was converted to OH by titration with NO directly below the sampling nozzle. The detection limit for the FAGE instrument during SOAPEX-2, determined by calibration in the field, was 1.4 xlO5 molecule cm-3 for OH and 5.4x 105 molecule cm-3 for HO2. A description of the instrument, as set up in previous field campaigns and dur-... 

The detection of HIV-related proteins is one of the most challenging tasks. This is especially true because AIDS should be diagnosed as early as possible to enable an early and effective therapy of this infection. Pavski and Le (57) used the aptamer strategy to detect reverse transcriptase (RT) of the type 1 human immunodeficiency virus (HIV-1). A direct and specific ACE method was proposed using laser-induced fluorescence (ACE/LIF) as detection principle. Single-stranded DNA aptamers as probes fluorescently labeled were synthesized. The resulting aptamer is specific for HIV-1 RT, and it exhibited no cross-reactivity with RTs of the enhanced avian myeloblastosis virus (AMV), the Moloney murine leukemia virus (MMLV), or denatured HIV-1 RT. An affinity complex of RT 26-HIV-l RT was stable, with calibration curves linear up to 50 nM (6 /xg/mL) HIV-1 RT concentration. Both... 

The extremely small cross sections for conventional Raman scattering, typically 10 111 to 10-25 cm2/molecule has in the past precluded the use of this technique for single-molecule detection and identification. Until recently, optical trace detection with single molecule sensitivity has been achieved mainly using laser-induced fluorescence [14], The fluorescence method provides ultrahigh sensitivity, but the amount of molecular information, particularly at room temperature, is very limited. Therefore, about 50 years after the discovery of the Raman effect, the novel phenomenon of dramatic Raman signal enhancement from molecules assembled on metallic nanostructures, known as surface-enhanced Raman spectroscopy or SERS, has led to ultrasensitive single-molecule detection. 

At York University, Toronto, microwave measurements have been revived by Storry and Hessels [9,10], that could benefit of lasers to excite the 23P level, instead of the lamps used by Hughes and coworkers. Also, the detection of laser-induced fluorescence from 23P levels makes another basic difference with respect to Hughes experiments, which, together with a microwave frequency scan, eliminated the lineshape asymmetries. In this experiment, a moderate magnetic field is also used to select the transitions between the desidered Mj sublevels. The... 

Energy disposal has been studied for the reactions F + IC1 [553] and I2 [554, 555] using laser-induced fluorescence detection of the IF product. For F + IC1, the results indicate a direct reaction with the IF vibrational product distribution being inverted with a peak at v — 7. As with the Cl and Br atom reactions, the majority of the reaction energy appears as IF internal energy ( 0.14). For F + I2, the IF product vibrational state distribution appears to be bimodal [554] with peak at v = 0 and a secondary peak at v = 18 with the distribution extending up to the limit imposed by the reaction exoergicity. Trajectory... 

Ulfelder KJ (1994) Quantitative capillary electrophoretic analysis of PCR products using laser-induced fluorescence detection. Applications Information Bulletin A-1774. Beckman Instruments, Inc., Fullerton, CA. 

Ultraviolet light is routinely used for detection however, laser-induced fluorescence of labeled DNA offers better results. For example, a PCR-amplifled DNA fragment comprised of 120-400 base pairs can be separated with a resolution up to four base pairs using 1% hydroxyethylcellulose and DB-17 capillary (60 cm effective length X 0.1 mm inner diameter with 0.1 jum phase thickness). Laser-induced fluorescence detection can yield a sensitivity of about 500 pg/mL of DNA (after staining with fluorescent intercalating dye YO-PRO-1) [14]. 

On the experimental side, the coupling of crossed molecular beam techniciues with sophisticated detection techniques (Laser Induced Fluorescence, CARS or REMPI spectroscopy, Rydberg tagging photoionisation using synchrotron radiation or U lasers) has improved considerably the detailed study of chemicid reactivity. It is now possible to prepare reactants in a well defined state and to analyze the reaction products at a fixed scattering angle for a. collision at a well defined kinetic energy [1]. 

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