Spectrofluorometer components

A variety of commercial instruments are available for PL measurements. These include spectrofluorometers intended primarily for use with liquids in a standard configuration, and simple filter-based systems for monitoring PL at a single wavelength. For use with opaque samples and surfaces, a few complete commercial systems are available or may be appropriately modified with special attachments, but due to the wide range of possible configuration requirements it is common to assemble a custom system from commercial optical components. 

Dyads (1 - 4) were synthesized by the method described previously. Fluorescence spectra were measured in degassed acetonitrile solutions at 2S °C with a Hitachi 8S0 spectrofluorometer. The excitation wavelength was the Soret maximum. Fluorescence lifetimes were measured at 25 °C using a Horiba NAES-500 ns-fluorometer interfaced to an NEC PC-9801 RX personal computer. The excitation light below 420 nm was cut off with a glass filter. The fluorescence was detected by a single-photon counting system and analyzed as the sum of two exponential components after deconvolution of the instrument response function. NMR spectra were recorded on a JEOL JNM GX-270 NMR spectrometer. 

Basic components of fluorometers and spectrofluorometers include (1) an excitation source, (2) an excitation monochromator, (3) a cuvet, (4) an emission monochromator, and (5) a detector. In Figure 3-17, these components are shown as they would be configured in a 90° optical system. 

FIGURE 15-8 Components of a fluorometoror spectrofluorometer. Source radiation is split tnlo two beams. The sample beam passes through the excitation wavelength selector to the sample. The emitted fluorescence is isolated by the emission wavelength selector before striking the transducer. The reference beam is attenuated before striking the transducer, The electronics and computer system compute the ratio of the fluorescence intensity to the reference beam intensity, which cancels the effect of source intensity fluctuations. 

Figure 9.3. Schematic diagram (top view) of the components of a fluorometer (filter fluorometer or spectrofluorometer). The source is a mercury-arc or xenon-arc lamp. The excitation grating or primary filter transmits only a portion of the radiation emitted by the source. Most of the exciting radiation passes through the sample cell without being absorbed. The radiation absorbed causes the sample to fluoresce in all directions, but only the emission that passes through the aperture or slit and through the secondary filter or fluorescence grating is measured by the phototube, or photomultiplier. The output of the detector is either measured on a meter or plotted on a recorder. From G. H. Schenk, Absorption of Light and Ultraviolet Radiation, Boston Allyn and Bacon, 1973, p 260, by permission of the publisher.

Components of an Uncorrected Spectrofluorometer. The design of filter fluorometers and spectrofluorometers has already been discussed here, we shall describe in more detail the components of an uncorrected spectrofluorometer (see Fig. 9.7). 

Uncorrected Spectrofluorometers for Research. This category of instrument is adaptable to all kinds of research, and is generally much more expensive than the medium-priced spectrofluorometers. The best known example is the Aminco-Bowman SPF instrument. The latter can be used as a spectrofluorometer, but with the attachment of an Aminco-Keirs phosphoroscope, it can also be used as a spectrophosphorimeter. When used as a spectrofluorometer, it consists of essentially the same components as those shown in Figure 9.7,... 

We now describe the individual components of a spec-trofluorometer. The general characteristics of these components are considered, along with the reason for choosing specific components. Understanding the characteristics of these components allows one to understand the cq>abilities and limitations of spectrofluorometers. We will first consider light sources. 

The components of fluorometers and spectrofluorometers are quite similar to those we have discussed for absorption photometers and spectrophotometers. However, several differences are discussed here.-... 

The intensity of fluorescence is directly proportional to the concentration of the fluorescent compound. If the target compound is not fluorescent, then it is converted into a fluorescent derivative by reaction with a suitable (nonfluorescent) reagent. The fluorescence emitted by the fluorescent compound is measured using a spectrofluorometer [6]. Most of the modem spectrofluorometers employ diffraction grating monochromators to select the appropriate wavelengths for maximum excitation and emission. The basic components of a fluorometer are a light source, an excitation monochromator, a sample holder, an emission monochromator, and a fluorescence detector as shown in Fig. 6.6. 

Figure 12.1 Schematic diagram of the configuration of the excitation and emission components in a spectrofluorometer.

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