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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 It might be outdated or ideologically biased.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 ?
San Jose, CA, September 09, 2016 --(PR.com)-- Turner Designs is very excited to partner with Wilhelmsen Ship Services (WSS) to supply the ballast water community with Ballast-Check 2, a small, hand-held fluorometer which enables quick, indicative checks of ballast water samples.
On the other hand, the measurements of fluorescence intensity used to assign ERF values were performed in fluorometers using suspensions of URB microspheres which included all populations of microspheres.
The other end was split into two branches connected to the excitation output and emission input slits of the fluorometer monochromators, respectively.
The first fluorometers were developed with red light (LEDs, Light-Emitting Diodes) as measuring or actinic light, i.e., PAM 2000 substituted by PAM 2500 and later fluorometers with broad band blue light (LEDs) were introduced i.e., Mini PAM, Water PAM, Junior PAM and Monitoring PAM (Walz GmbH, Effeltrich, Germany) and Pocket PAM (Gademann Instruments Wurzburg, Germany) or with narrow wavelengths as measuring and actinic light as Phyto PAM and Multicolor PAM (Walz GmbH, Effeltrich, Germany) (Table 2).
Chl a fluorescence was measured using a pulse amplitude modulation (PAM) fluorometer (Schreiber et al..
WET Laboratories FLRHB submersible fluorometers (WET Laboratories Inc., Philomath, OR) positioned at the 4 station locations recorded fluorescence once every 5 min, at 1-sec intervals, for a duration of 1 min.
Thus, in most current field fluorometers, in which the light flashes utilized induce multiple turnovers of PSII, one can consider the PQ pool as the terminal sink for the electrons extracted from water at PSII.
Pairing scientists with engineers, the 40-employee company makes fluorometers, transmissometers, scattering sensors and spectrophotometers, all of which collect data from the ocean and beam the information back to the surface, helping scientists learn about important changes in the food chain.
Ashjian's team used nets to sample plankton; instruments called CTDs to measure water temperatures, salinities, and depth; and a variety of sensors, including backscatter sensors to measure particles and fluorometers to measure amounts of plant pigment in the water.
Next, there are five chapters related to photosynthesis, including a discussion of photosynthetic pigments, gas exchange using infra red gas analyzers and oxygen electrodes, and chlorophyll fluorescence using fluorometers with and without the capability to do modulated fluorescence.
The Turner Designs Ballast-Check 2 is one of three fluorometers included in the validation study.
Boris Rotman, said that FiBIR technology will propel the development of next-generation fluorometers to be used across the life science industry in applications ranging from live cell imaging, to PCR, ELISA and Next Generation Sequencing.