Ultraviolet-visible spectrophotometers applications

Some commercially available instruments, in addition to visible spectrophotometers, can also perform measurements in the ultraviolet and near IR regions of the spectmm. These have not yet found extensive application in the field of water analysis. 

See for example E. I. Stearns, Applications of ultraviolet and visible spectrophotomet-ric data, in M.G. Mellon (ed.), Analytical Absorption Spectroscopy Ahsorptimetry and Colorimetry (New York Wiley, 1950), 306-438. For Barnes and the American... 

The selective absorption of ultraviolet, visible and infrared radiation by molecules is explained in a descriptive manner that stresses how the noncontinuous energy requirements of chemical substances can only be satisfied by photons that have energy values equivalent to that of the differences in energy levels of the molecule in question. The meaning and quantitative significance of Beer s Law is briefly discussed. The components of a simple spectrophotometer are illustrated, accompanied by a demonstration of the operation of a spectrophotometer in the laboratory. Actual applications of the techniques of spectrophotometry are described during the presentation of relevent topics, for example, in drug identification. 

Ultraviolet spectrophotometers cont.), single-beam, 225 standardisation, 226 Ultraviolet spectrophotometry, 221-232 absorption cells, 226 colorimetry, 228 derivative, 230 difference method, 229 dual-wavelength, 229 identification by, 231 influence of pH, 224 influence of solvent, 224 laws of absorption, 222 quantitative applications, 227 stray-light effects, 224 Ultraviolet-visible detector, 202 multiwavelength, 211 Unicontin, 1011 Unidiarea, 474 Unidone, 356 Uniflu, 557, 893 Unilobin, 709 Unimycin, 846 Uniphyllin, 1011 Uniprofen, 677 Unisom, 576... 

Table 16-1 gives the rough limits of each of the three regions. Measurements in the near-lR region are often made with photometers and spectrophotometers similar in design and components to the instruments described in earlier chapters for ultraviolet-visible spectrometry. The most important applications of this spectral region have been to the quantitative analvsis of industrial and agricultural materials and for process control. Applications of near-IR spectrometry are discussed in Section 17D. 

Absorption spectrophotometry in the ultraviolet, visible, and near-infrared spectral regions has become an extremely important analytical tool in the last two decades, its progress having been greatly accelerated by the development of commercially available recording spectrophotometers. This paper briefly discusses its history, describes laboratory techniques, and cites many practical applications from the chemical literature. It is intended both to introduce the novice to the field and to acquaint the specialist with the versatility of these techniques. 

This is primarily engaged in analysis of boiler water treatment matters and involves on-site studies of various problems and the chemical examination of corrosion products, boiler scales, etc. It can also carry out certain types of metallurgical, fuel and inorganic analysis. Normal wet methods of analysis coupled with a visible ultraviolet and atomic absorption spectrophotometer are used for a wide range of analytical applications. Equipment in use by the engineering insurers providing these services can include an ion chromatograph, spectrometer equipment, atomic... 

Diphenyldiazine, more commonly known as azobenzene, exists in two isomers, the cis and the trans. The more stable trans isomer can be converted to the cis form by the application of ultraviolet radiation. Reagent grade azobenzene normally has about 1 % of the cis isomer present. However, if a solution of this compound is exposed to uv radiation, the concentration of the cis isomer can be increased. Both compounds are highly colored and easy to measure with a visible region spectrophotometer. The trans isomer is quite nonpolar and will not be retained on a polar alumina column. The cis isomer is quite polar and will be retained at the top of the column. 

---