(redirected from fluorimetric)
Also found in: Dictionary, Medical.


An instrument that measures the fluorescent radiation emitted by a sample which is exposed to monochromatic radiation, usually radiation from a mercury-arc lamp or a tungsten or molybdenum x-ray source that has passed through a filter; used in chemical analysis, or to determine the intensity of the radiation producing fluorescence. Also spelled fluorimeter.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



(also fluorimeter), an instrument used for measuring the decay time τ of fluorescence, which is approximately 10–8–10–9 sec. A fluorometer operates on the following principle. During high-frequency modulated excitation of luminescence, the luminescence is modulated at the same frequency as the excitation; however, because of the finite duration of the luminescence emission, the phase of the luminescence modulation lags behind that of the excitation modulation. In the case of excitation that is sinusoidally modulated at a frequency ω and fluorescence that decays exponentially, the phase angle φ = tan–1 (ωτ). The relation between the amplitude A0 of the excitation modulation and the amplitude A of the luminescence modulation is Fluorometer. Thus, to determine τ either φ or the ratio A0/A must be measured. If the decay is not exponential, the same method may be used to establish the mean lifetime of the excited state and to estimate the extent to which the decay is not exponential.

Figure 1. Schematic diagram of a phase fluorometer

The most widely used fluorometers are phase fluorometers, which measure φ (Figure 1). In an optical-excitation phase fluorometer, a light beam from a source (1) is focused on a modulator (2). A portion of the modulated flux is deflected by a semi-transparent plate (3) and enters a photomultiplier (5). The remainder of the flux is focused on a specimen (4) to excite fluorescence, which is deflected to another photomultiplier (6). The phase difference φ between the photoelectric currents from (5) and (6) is measured by means of a phase meter (7). A cathode-ray tube or phase detector (8) serves as the phase indicator. Fluorometers based on electron-beam and X-ray excitation have also been developed.

In an instrument that is more advanced than a fluorometer, luminescence is excited by short light pulses, and the decay curve is recorded directly.

Instruments that are used for luminescence analysis are also called fluorometers, or fluorimeters. Such instruments measure the intensity of luminescence and contain both a source for exciting the luminescence and a photometer.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
fluorimetric determination of thiamine by the thiochrome method," Journal of Pharmaceutical and Biomedical Analysis, vol.
Efstathiou, "Flow-injection fluorimetric determination of 1,4-benzodiazepines in pharmaceutical formulations after acid hydrolysis," Journal of Pharmaceutical and Biomedical Analysis, vol.
Molina-Diaz, "Fluorimetric SIA optosensing in pharmaceutical analysis: determination of paracetamol," Journal of Pharmaceutical and Biomedical Analysis, vol.
Tyrosine was assayed by a fluorimetric method as previously described (16).
ACE activity was measured by the hydrolysis of two synthetic substrates (Z-FHL and HHL) in a sensitive fluorimetric assay, as described previously.
Fluorimetric titrations of the SULT:PAP complexes with PCP show cooperative fluorescence quenching as previously reported, which suggests normal subunit interactions.
The caspase 3 activity in renal tissue was measured by caspase 3 fluorimetric assay kit (Sigma Chemicals, USA) as per manufacturer's instruction.
All 3 enzymatic activities were measured with a plate-reader fluorimeter using the fluorimetric substrate 4-methylumbelliferyl-a-glucoside.
High-pressure-liquid-chromatographic and fluorimetric methods for the determination of adenine released from ribosomes by ricin and gelonin.
Analyses of PAHs are generally performed by high performance liquid chromatography (HPLC) coupled with UV-visible or fluorimetric detector (FLD) and gas chromatography (GC) with mass spectrophotometer (MS).
Wu, "Determination of rutin with UV-Vis spectrophotometric and laserinduced fluorimetric detections using a non-scanning spectrometer," Analytical Letters, vol.
[13.] Clemmesen C, Kiel DW (1990) Improvements in the fluorimetric determination of the RNA and DNA content in individual marine fish larvae.