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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.



(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.

References in periodicals archive ?
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.
The company plans other physical configurations, such as automated fluorometers using FiBIR cartridges for nanolitre samples as well as multi-sample cartridges for high-throughput analysis.
The first fluorometers were developed with red light (LEDs, Light-Emitting Diodes) as measuring or actinic light, i.
Chl a fluorescence was measured using a pulse amplitude modulation (PAM) fluorometer (Schreiber et al.
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.
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.
Changes in seston concentration are revealed in the field by the fluorometers, and the sampled water can be analyzed in the laboratory for various seston parameters.
VICAM makes single-use test kits for detecting the presence of mycotoxin and microbiological organisms in food products as well as immunoaffinity columns for the isolation of contaminants for measurement by fluorometers, HPLC or LC/MS.
The output signal from the indicator organism can be adapted to match existing instruments such as fluorometers, colorimeters, or luminometers.
Fluorometers that utilize optical filters to select excitation and emission wavelengths are called filter fluorometers.