Visible light spectrophotometry

H Hirashima and M Sumimoto. Fundamental Properties of Mechanical Pulp Lignins. I. Visible Light Spectrophotometry and Nitrobenzene Oxidation. J. Japan Wood Res. Soc. 32 705-712, 1986. 

NIOSH method 6015, Colorimetric determination of indophenol by visible light spectrophotometry... 

Cuvettes used for UV-VIS spectrophotometry must be transparent to all wavelengths of light for which it is used. If visible light is used, the material must ideally be completely clear and colorless, which means that inexpensive materials, such as colorless plastic and ordinary colorless glass, are perfectly suitable. A case of 500 plastic 1-cm-square cuvettes may cost as little as 50. However, ordinary colorless glass and plastic are not transparent to light in the ultraviolet region. For ultraviolet spectrophotometry, the cuvettes must be made of quartz, which is more expensive. A matched set of two cuvettes to be used in a doublebeam spectrophotometer may cost as much as 400. 

Quantitative analysis is also possible. The spot representing the component of interest can be cut (in the case of paper chromatography) or scraped from the surface (TLC), dissolved, and quantitated by some other technique, such as spectrophotometry. Alternatively, modern scanning densitometers, which utilize the measurement of the absorbance or reflectance of ultraviolet or visible light at the spot location, may be used to measure quantity. 

Spectrophotometry is any technique that uses light to measure chemical concentrations. A procedure based on absorption of visible light is called colorimetry. The most-cited article in the journal Analytical Chemistry from 1945 to 1999 describes a colorimetric method by which biochemists measure sugars.4... 

Developments in traditional forms of spectrophotometry, as well as new methods, could find greater use in ocean measurements. Spectroscopy based on absorption of visible light may have reached a limit in its traditional form, however. Spectrophotometry will remain in wide use due to its ease, low cost, and great versatility. In many ways it remains the first choice for analysis, but its low sensitivity makes it useful for a rather limited spectrum of analytes. 

A water soluble activated ester of methoprene (Figure 5, Structure 16) was also prepared from sodium l-hydroxy-2-nitro-4-benzene sulfonate (16). The amount of compund 16 in crude preparations which contained both compound 16 and the free dianion (Figure 5, Structure 17) was determined by spectrophotometry in aqueous solution. Upon hydrolysis compound 16 yielded the dianion (Structure 17) which absorbed visible light at 406 nm in the presence of nucleophiles (Figure 5). Two absorbance readings were required to determine the amount of compound 16 present in the crude material. 

Upstone SL. Ultraviolet/visible light absorption spectrophotometry in clinical chemistry. In Meyers RA, ed. Encyclopedia of analytical chemistry Applications, theory, and instrumentation. New York John Wiley Sons, 2000 1699-713. 

The analytical methods used for testing the between-bottle homogeneity were visible light or UV spectrophotometry (Fe, Cl and P), ETAAS (AI and Mn), FAES (K and Na), FAAS (Ca and Mg) and flow injection turbidimetry measurement (S as sulphate). The results did not reveal any significant between-bottle variability and it was concluded that both batches were homogeneous. 

There are two commonly used sources of light in UV-visible absorption spectrophotometry, hydrogen or deuterium discharge lamps and incandescent filament... 

Solutions of Ni(n-butyl dtc)sBr in basic solvents are bleached by visible light to nickel (II) complexes and thiuramdisulfide. The reaction is reversible in CH3CN, and the rate of return to the nickel (IV) cations can be studied conveniently with spectrophotometry. The experimental data (26) are consistent with a rate law (Equation 11) in which thiuram disulfide-L2 and halide both play a role. 

Iodine in inert solvents such as hexane or carbon tetrachloride forms violet solutions containing I2 molecules which absorb in the visible. When such a solution is subjected to a microsecond flash, the absorbance decreases during the flash and afterwards returns to its original value at a rate that is easily monitored by microsecond flash spectrophotometry. Typical oscilloscope traces, representing optical intensity changes with time, are similar in form to that shown in Figure 4.9(b) above. The return follows second-order kinetics. The evidence indicates that iodine molecules are dissociated by the flash into atoms (which do not absorb visible light) and that the atoms subsequently combine ... 

The most commonly used method for the direct observation of mixtures of ionic species (i.e. anions and cations) and molecular species, at a known pH, is spectrophotometry (ultra-violet or visible). This is described in Chapter 4. Whereas potentiometry enables an ionization constant to be determined in about 20 minutes, spectrophotometry takes at least half a working day. Nevertheless, it is particularly suitable for sparingly soluble substances and also for work at high and low pH values which are beyond the range of the glass electrode. It can be used only for substances which absorb ultra-violet or visible light, and the relevant ionic and molecular species must have different spectra. This method is related to potentiometry in that the spectra are determined in buffers whose pH values are measured by potentionietry. Other spectromctric methods, available for specialized purposes, depend on the same principle. 

Upstone, S.L., 2000. In Meyers, R.A. (Ed.), Ultraviolet/Visible Light Absorption Spectrophotometry in Clinical Chemistry. Encyclopedia of Analytical Chemistry. John Wiley Sons Ltd, Chichester, pp. 1699-1714. 

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. 

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