Ultraviolet measurements

Samuelsen [345] has reported an HPLC method for the determination of trichlorfos and dichlorvos in seawater. A methyl cyanide phosphate buffer was used and detection was achieved by ultraviolet measurements at 205 nm. 

Spectrophotometric measurements of nalidixic acid have been reported. Gafari et aJL(41) used an extraction with ultraviolet measurement at 255 or 327 nm for blood and tissue samples. Takasugi and co-workers extracted buffered tissue homogenate with chloroform and measured the optical density at 334 nm.(13)... 

Spectral data (Amax and AE, and e x 10 3) for the pyrimidine bases investigated in a few representative papers are collected in Table XXVIII. The absorption bands are denoted by the capital letters A, B, C, etc. In Table XXVIII we have listed the results of the vacuum ultraviolet measurements by Yamada and Fukutome428 (cf. also ref. 429), who measured the spectra of sublimed films of cytosine, thymine, uracil (and also of guanine and adenine) down to 120 nm at room temperature. Several remarkable absorption peaks were found below 190 nm in addition to the already known ones near 260 and 200 nm. A weak absorption at 230-240 nm in cytosine was not indicated in the sublimed films of the molecule,428 but was visible in the stretched polyvinyl alcohol film spectrum.432 Crewe et al.i3° studied the interactions of fast electrons with the five nucleic acid bases and measured the energy-loss spectra of 20 keV electrons transmitted through thin films of these bases. These last data are also listed in Table XXVIII for comparison with the other spectral findings. 

Torres O. And Bhartia P.K., Impact of tropospheric aerosol absorption on ozone retrival from backscattered ultraviolet measurements, J. Geophys. Res., 104, 21569-21577, 1999. 

Joiner, J. and Bhartia, P.K. (1995) The Determination of Cloud Pressures from Rotational-Raman Scattering in Satellite Backscatter Ultraviolet Measurements, J. Geophys. Res., 100, pp. 23,019-23,026. 

Joiner, J., Bhartia, P.K., Cebu la, R.P., Hilsenrath, E McPeters, R.D., and Park, H. (1995) Rotational-Raman Scattering (Ring Effect) in Satellite Backscatter Ultraviolet Measurements, Appl. Opt., 34, pp. 4513-4525. 

A short column packed with an amine bonded polymer (weak anion exchange material) connected prior to the anion separation column was found to be very effective for the selective removal of humic substances prior to anion separation by ion chromatography. About 500 sample injections could be performed before breakthrough of humic substances occurred as indicated by ultraviolet measurements made on the eluate at 225nm. 

Since many atmospheric pollutants such as ozone have absorption bands in the ultraviolet, measurements have also been performed in this spectral region. Recently, it was shown that phase locking within the filaments results in enhanced third harmonic generation [46]. Then, the build-up of the ultraviolet supercontinuum was characterized over both the laboratory and the atmospheric scales. The UV-visible part of the continuum measured in the laboratory with a single filament is presented in Fig. 15.7. At the beginning of filamentation, a third harmonic band with 20 nm bandwidth is generated around 270 nm. Two meters further, the intensity of the third harmonic is reduced and a plateau appears in the UV-Visible region be-... 

Pyrazines with hydroxyl groups are generally in the oxo form however, substituents like chlorine may profoundly influence the position of the tautomeric equilibria. Ultraviolet measurements indicate that in ethanol solution 2-chloro-6-hydroxypyrazine (125a) exists predominantly in the hydroxy rather than in the oxo form (125b) 272 trifluorohydroxypyrazine also does not tautomerize appreciably to a pyrazinone.279... 

Although we must anticipate the discussion of optical rotatory dispersion as applied to proteins, it is relevant to mention here the ultraviolet measurements upon myoglobin which have already been described in connection with the issue of helical sense (see Section III, D). The agreement of these measurements upon myoglobin in solution with helical content in the crys-... 

The absorption of ozone in the visible spectrum is especially useful and has been used in analyzing some of the Smithsonian data, which are extensive but do not extend to include an appreciable amount of the ultraviolet region. Wulf (61) and others (14, 25) have made considerable use of these data, deducing ozone concentrations which are in fairly good agreement with those obtained through the use of ultraviolet measurements. 

The limitations of early instrumentation were extreme. Engineers were first able to get on-line measurements for only the simplest process parameters - initially only temperature and pressure. As interest in on-line measurements grew, various manufacturers developed instrumentation for chemical process streams. Soon, instrumentation was available for simple infrared measurements, water determination, simple ultraviolet measurements, density, and viscosity. The spectroscopic instruments (1R, UV, etc) of this era were simplistic devices similar to colorimeters that used filters to provide the appropriate frequency or range of frequencies to quantitate one or more components of the process stream. 

By ultraviolet measurement this value was found to be quite similar, 87°C, for a 0.004 % solution. 

Ultraviolet measurements (250 - 450 nm) are carried out on the following four solutions ... 

In the study of the biogenesis and the transformation of steroids by the adrenal gland, the technique of paper chromatography applied to steroids by Zaffaroni and co-workers - has proved an invaluable aid to research, particularly where minute quantities of material were involved. Other ultramicro techniques for measuring adrenocortical hormones, such as the ultraviolet scanner and the automatic ultraviolet measuring fraction collector, have likewise been of considerable assistance. A variety of color reactions and similar analytical determinations have been widely employed in the study of the hormones and their metabolic transformation products. - ... 

Styrenated fatty acids and alkyd resins spectrophoto-metric analysis using a modified Kappelmeier procedure, with ultraviolet determination of polymerized styrene Styrene and fumerate in esters and resins 0.1-2% styrene in polystyrene at 250-260 m/i direct determination polystyrene in a copolymer in chloroform solution at 269 mu partial separation, nitration, and determination as neutralized p-nitrobenzoic acid, of bound styrene in raw and cured polymers, using a three-wavelength ultraviolet measurement to check for unexpected interfer-... 

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