Visible spectrophotometry

The evaluation of instrumentation for molecular UV/Vis spectroscopy is reviewed in the following pair of papers. Altermose, 1. R. Evolution of Instrumentation for UV-Visible Spectrophotometry Parti, /. Chem. Educ. 1986, 63, A216-A223. 

Hydantoin derivatives show weak absorption in the uv-visible region, unless a part of the molecule other than the imidazohdinedione ring behaves as a chromophore (13) however, piC values have been determined by spectrophotometry in favorable cases (14). Absorption of uvby thiohydantoins is more intense, and the two bands observed have been attributed to n — tt and n — tr transitions of the thiocarbonyl group (15,16). Several piC values of thiohydantoins have been determined by uv-visible spectrophotometry (16). 

S. Gitritg, Ultraviolet—Visible Spectrophotometry in Pharmaceutical Analysis, CRC Press, Boca Raton, Fla., 1995. 

There is a large amount of Hterature on the analysis of dyes and the most comprehensive treatment of the analytical chemistry of dyestuffs is found in Reference 271. Earlier papers dealing with the analytical chemistry of dyes in the environment mainly used paper, thin-layer, column, and high pressure hquid chromatography and ultraviolet and visible spectrophotometry (255,272—275). 

Optical methods of analysis are dependent either upon (i) measurement of the amount of radiant energy of a particular wavelength absorbed by the sample, or (ii) the emission of radiant energy and measurement of the amount of energy of a particular wavelength emitted. Absorption methods are usually classified according to the wavelength involved as (a) visible spectrophotometry (colorimetry), (b) ultraviolet spectrophotometry, and (e) infrared spectrophotometry. 

Fig. 17.8 Reproduced with permission from J. E. Steward (Ed.), Introduction to Ultraviolet and Visible Spectrophotometry, 2nd edn, Philips/Pye Unicam, Cambridge, 1985.

UV-visible spectrophotometry and fluorescence spectrophotometry are also used for the direct observation of radical species and their reactions in some... 

Some preliminary laboratory work is in order, if the information is not otherwise known. First, we ask what the time scale of the reaction is surely our approach will be different if the reaction reaches completion in 10 ms, 10 s, 10 min, or 10 h. Then, one must consider what quantitative analytical techniques can be used to monitor it progress. Sometimes individual samples, either withdrawn aliquots or individual ampoules, are taken. More often a nondestructive analysis is performed, the progress of the reaction being monitored continuously or intermittently by a technique such as ultraviolet-visible spectrophotometry or nuclear magnetic resonance. The fact that both reactants and products might contribute to the instrument reading will not prove to be a problem, as explained in the next chapter. 

Other methods reported for the determination of beryllium include UV-visible spectrophotometry [80,81,83], gas chromatography (GC) [82], flame atomic absorption spectrometry (AAS) [84-88] and graphite furnace (GF) AAS [89-96]. The ligand acetylacetone (acac) reacts with beryllium to form a beryllium-acac complex, and has been extensively used as an extracting reagent of beryllium. Indeed, the solvent extraction of beryllium as the acety-lacetonate complex in the presence of EDTA has been used as a pretreatment method prior to atomic absorption spectrometry [85-87]. Less than 1 p,g of beryllium can be separated from milligram levels of iron, aluminium, chromium, zinc, copper, manganese, silver, selenium, and uranium by this method. See also Sect. 5.74.9. 

The complex of Sn(IV) ions and pyrocatechol violet (2) in a flow system is concentrated on Sephadex QAE A-25 gel and subsequently determined by visible spectrophotometry at 576 nm. The linear range of the method is 2-40 pg/L with LOD 0.3 pg/L27a. 

It therefore became more convenient to monitor the reaction progress with UV/Visible spectrophotometry, because all the pyridine N-oxides have strong absorption bands near 330 nm, with e 103Lmol 1cm 1. Two approaches for the analysis of the kinetic data were used. In the first but much less precise method, the initial reaction rates were calculated from the objective method of fitting the experimental values of [PyOL to this function (30) ... 

Figure 7.5 Schematic diagram of a high performance liquid chromatography (HPLC) system. The solvent(s) are pumped through the system, and the sample injected just before the column where separation occurs. Detection is often by UV/visible spectrophotometry at a fixed wavelength.

Can cuvettes used for visible spectrophotometry be made of plastic Explain. 

Cuvettes for visible spectrophotometry can be made of clear, colorless plastic. The only requirement is that none of the visible fight wavelengths be absorbed, which is the reason that they must be colorless. 

Chapter 1 is an introduction to the field of molecular fluorescence, starting with a short history of fluorescence. In Chapter 2, the various aspects of light absorption (electronic transitions, UV-visible spectrophotometry) are reviewed. 

The study of molecular complexation was then extended to other aromatic nitro derivatives125. Although, as was described before, one of the more frequent methods of studying the formation of molecular complexes is by UV-visible spectrophotometry, the author did not observe detectable differences in the UV-visible absorbance spectra between the 2-hydroxypyridine-l-fluoro-2,4-dinitrobenzene (FDNB) mixtures and the sum of their separate components. The author observed that the signals of the 1II NMR spectra of FDNB in apolar solvents were shifted downward by the addition of 2-hydroxypyridine from solutions where [2-hydroxypyridine] [FDNB] he calculated the apparent stability constants, which are shown in Table 13. 

A new water-soluble calix[4]arene-triacid-monoquinone (99) has been synthesized and its ion-binding properties in aqueous solution were investigated by means of voltammetry and UV-visible spectrophotometry. The electrochemical behaviour of (99) is dependent on the concentration of Ca + ion rather than that of other alkaline... 

After s)mthesis it is important to determine the drug s exact chemical structure. This will involve a variety of techniques such as mass spectrometry, nuclear magnetic resonance (H and C ), infrared and ultraviolet/visible spectrophotometry along with elemental analysis. This will confirm the medicinal chemist s proposed... 

Because various swinging bucket centrifuges behave differently with respect to acceleration and braking, some optimization of centrifugation conditions may be advisable. This can be readily accomplished by UV and visible spectrophotometry if one uses BSA (or some other inexpensive protein sample) along with a small amount of dichromate as a yellow colored metal ion species. 

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