Spectrofluorometer corrected

Fluorescence spectra of the novolac samples were measured on a Spex Fluorolog 212 spectrofluorometer with a 450 W xenon arc lamp and a Spex DM1B data station. Spectra were taken with front-face Illumination using a 343 or 348 nm excitation wavelength for solutions or films, respectively, which are near the maximum transmission region of this spectrometer. Spectra were corrected using a rhodamlne B reference. Monomer fluorescence was measured at 374 or 378 nm and exclmer fluorescence was measured at 470 nm. Monomer and exclmer peak heights were used In calculations of Ie/Im. The 1 monomer peak of pyrene was used to reduce overlap with the exclmer emission. 

Spectrofluorometers equipped with a photodiode instead of a quantum counter provide excitation spectra that should be further corrected because, in addition to the reasons explained above, the wavelength response of the photodiode is not strictly flat over the whole wavelength range available. 

Compounds 1,2,3,5,10,11,12,13,14 were dissolved in EPIP (diethyl ether, petroleum ether, isopropanol 5 5 2)whereas compounds 4,6,7,8,9,15 were dissolved in THF-DE (tetrahydrofurane, diethyl ether 1 1). These solvent mixtures can be frozen as glassy samples at 77 K. The absorption spectra were recorded on a standard spectrophotometer SF-10 or Beckman-5270. The measurements of fluorescence excitation and emission spectra were made with the aid of a spectrofluorometer SLM-4800 with automatic correction of spectral response. Fluorescence lifetimes were measured with the aid of a pulse fluorometer PRA-3000. Magnetic circular dichroism (MCD) measurements were carried out in a 8 kG magnetic field using a JASCO J-20 circular dichrometer. Triplet state formation was observed for investigated compounds at the experimental set up, whose detailed description can be found in our paper (27). The optical experiments were carried out with a porphyrin concentration of 4.10- - 4.10 mol.l". In NMR investigations (Bruker WM-360) we used higher concentrations ( 5.10" raol.l ) and dried solvents (CDCl, C 2 and toluene-d0). 

A quantum-corrected fluorescence spectrum of TC HC1 (11 mg/50 ml) in 0.05 N NaOH taken with a Perkin-Elmer spectrofluorometer LS 5 is given in Fig. 12. Various fluorimetric methods of determination of tetracycline antibiotics are reported in literature (116, 117, 118, 119, 120). TC can be dehydrated to ATC by heating in acid solutions and taking the advantage of the greater lipophilicity of ATC it is extracted at about pH 4 - 5 with chloroform and then the fluorescence of aluminium-chelate is measured (116, 121). 

All the spectral data presented in this chapter were taken in a spectrofluorometer that was spectrally corrected from 510 to 750 nm by a quantum counter containing tetra-f-butyl metal-ffee phthalocycanine in 1,1,2-tricholoroethan ( 1.2 x 10 M). Details of the procedures have been described in Ref. 29. 

The room temperature luminescent spectra of sintered ceramic were recorded by a spectrofluorometer (Fluorolog-3, Jobin Yvon, Edision, USA) equipped with Hamamatsu R928 photomultiplier and a 450 W Xenon lamp. The upconversion luminescent spectra were measured by the same equipment using a 980 nm continuous wave diode laser as excitation source. All the emission spectra were corrected for the setup characteristic. 

Figure 9.1. Spectra of uranyl nitrate. A The corrected emission spectrum of 10 M uranyl nitrate in 0.1 N ff2

Medium-priced uncorrected spectrofluorometers, inexpensive enough to be used for routine analytical work. (2) Uncorrected research spectrofluorometers, more expensive and adaptable for many different types of investigation one such instrument, for example, can be fitted with a phosphorescence attachment (including a rotating can) that converts it into a spectrophosphorimeter. (3) Corrected, or absolute, spectrofluorometers that directly record fluorescence excitation and emission... 

A xenon-arc lamp is used as the source in most spectrofluorometers, since it emits continuously over the range 200-700 nm (see Fig. 9.4C) and hence can be used to obtain fluorescence excitation spectra as well as emission spectra. (Emission spectra for many substances could be obtained with a mercury-arc source, but excitation spectra could not, because the emission is discontinuous and the frequency range is so limited.) However, in uncorrected instruments using a xenon-arc lamp, no correction is made for the variation in intensity of the source with changing wavelength. 

All spectrofluorometers are equipped with high-gain photomultipliers as detectors this partly compensates for the smaller amount of energy that gratings transmit compared to filters. However, uncorrected spectrofluorometers do not compensate for the variable response of the photomultiplier at varying wavelengths, so the measured relative intensities of two fluorescence-emission bands of a given species are not a correct indication of the true intensities. 

Corrected Spectrofluorometers. To obtain absolute spectra, the spectra obtained on uncorrected spectrofluorometers must be corrected point by point for instrumental parameters that vary with wavelength. Such corrections are tedious, and it is desirable to obtain spectra on a corrected spectrofluorometer if possible. These instruments correct for variations in the intensity of the xenon source so that the sample is excited at constant energy at all wavelengths, and for variations with wavelength in the response of the photomultiplier emission spectra are presented directly in quanta per unit bandwidth. 

Fluorescence excitation and emission spectra were recorded with an SLM 8000 spectrofluorometer. They are not corrected for instrumental effects. Absorption was measured with a Spectronic 200 spectrophotometer. An Orion 501 pH meter was used to determine pH. 

Steady-state and time-resolved fluorescence spectroscopy Absorption and fluorescence spectra were measured with a Hitachi 557 spectrophotometer and a Hitachi 850 spectrofluorometer, respectively. The time-resolved fluorescence spectra were measured with the apparatus reported previously [4,6] in principle, the time-correlated single photon counting system under a low excitation condition. The pulse intensity (540 nm, 6 ps (fwhm)) was in a range of 10 to 10 photons/cm. The time resolution of our optical set-up was 6 ps. Correction of spectral sensitivity and data treatment were carried out as reported previously [4,6]. 

Modern computerized spectrofluorometers often achieve a similar correction by storing the reference spectrum of the source in computer memory. After the sample spectrum is scanned, the correction is made by calculating the ratio of the sample spectrum to the reference spectrum. 

Determination of AGEs is based on the classic spectrofluorimetric detection 18-19. Fluorescence intensity was recorded at the emission maximum 440 nm upon excitation at 370 nm and at emission maximum 385 nm upon excitation at 335 nm for pentosidine fluorescence Fluorescence intensity is expressed in arbitrary units (AU) and corrected for dilutions. We employ a SPECTRAmax Gemini XPS spectrofluorometer with SOFTmax PRO software (Molecular Devices, Sunnyvale, CA). 

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