Spectrophotometer prism

Optical Applications. Vitreous siUca is ideal for many optical appHcations because of its excellent ultraviolet transmission, resistance to radiation darkening, optical polishing properties, and physical and chemical stabiUty. It is used for prisms, lenses, cells, wiadows, and other optical components where ultraviolet transmission is critical. Cuvettes used ia scatter and spectrophotometer cells are manufactured from fused siUca and fused quart2 because of the transmissive properties and high purity (222). 

Quartz also has modest but important uses in optical appHcations, primarily as prisms. Its dispersion makes it useful in monochromators for spectrophotometers in the region of 0.16—3.5 m. Specially prepared optical-quality synthetic quartz is requited because ordinary synthetic quartz is usually not of good enough quality for such uses, mainly owing to scattering and absorption at 2.6 p.m associated with hydroxide in the lattice. 

Traditional infrared spectrophotometers were constructed with mono-chromation being carried out using sodium chloride or potassium bromide prisms, but these had the disadvantage that the prisms are hygroscopic and the middle-infrared region normally necessitated the use of two different prisms in order to obtain adequate dispersion over the whole range. 

In a simple flame (emission) photometer an interference filter (Section 17.7) can be used. In more sophisticated flame emission spectrophotometers which require better isolation of the emitted frequency, a prism or a grating monochromator is employed. 

Spectrophotometer grating prism with 10 nm band width xenon lamp [G] [LD ] [L-ns]12 Phototaxigraph. Rate photoaccumulation. Spectrum is of relative efficiency (as a function of incident intensity) to produce constant response Diehn23)... 

This layer is then analysed directly by internal reflectance infra-red spectroscopy. Since there is no handling of the sample, contamination is reduced to a minimum. However, only infra-red spectral analysis is possible with this system since the material absorbed on the germanium prism is always a mixture of compounds, and since the spectrophotometer used for the production of the spectra is not a high-precision unit, the information coming from this technique is limited. While identification of specific compounds is not usually possible, changes in spectra, which can be related to the time of day, season, or to singular events, can be observed. 

Flame photometer or spectrophotometer incorporating nebulizer and burner, filters, prism or grating monochromator, photocell or photomultiplier detection system. 

Filter-photometer or spectrophotometer incorporating prism or grating monochromator, phototube photomultiplier or diode array, glass, quartz or plastic cells. 

For visible region the lenses and prisms of ordinary glass can be used but since glass is opaque to radiation of shorter wave lengths in ultraviolet spectrophotometers they are made of quartz. In infra red spectrophotometers they are made of large crystals of NaCl, CsF or KBr. 

Let us dwell on Figure 6.4 for a moment. The standards and sample solutions are introduced to the instrument in a variety of ways. In the case of a pH meter and other electroanalytical instruments, the tips of one or two probes are immersed in the solution. In the case of an automatic digital Abbe refractometer (Chapter 15), a small quantity of the solution is placed on a prism at the bottom of a sample well inside the instrument. In an ordinary spectrophotometer (Chapters 7 and 8), the solution is held in a round (like a test tube) or square container called a cuvette, which fits in a holder inside the instrument. In an atomic absorption spectrophotometer (Chapter 9), or in instruments utilizing an autosampler, the solution is sucked or aspirated into the instrument from an external container. In a chromatograph (Chapters 12 and 13), the solution is injected into the instrument with the use of a small-volume syringe. Once inside, or otherwise in contact with the instrument, the instrument is designed to act on the solution. We now address the processes that occur inside the instrument in order to produce the electrical signal that is seen at the readout. 

A spectrophotometer is an instrument which is capable of isolating monochromatic radiation or that which specifically contains a dispersing element a prism or a grating. 

The important uses of lithium fluoride are as flux in glasses, vitreous enamels and glazes in soldering and welding aluminum and its prisms in infrared spectrophotometers. The compound also is used for storing solar energy. 

Spectra were obtained with a Perkin-Elmer Model 13 spectrophotometer (double beam) modified to scan and record linearly in frequency [9]. A calibrated LiF prism was used with estimated frequency accuracy rh 4 cm"1. The spectral slit- width was about 9 cm "1 at 3600 cm"1 and 6 cm"1 at 3000 cm 1v Transmission accuracy is estimated at 0 5% in the region 30-50% T, where most measurements were made. The zero and 100% transmission values were measured for each spectrum, and a correction was applied for false energy. 

For the study of the first overtones of the O—H, N—H, and C—H bonds, situated in the range from 8000 to 5500 cm-1 we used a double beam recording autocollimating spectrophotometer with glass prisms, similar to that described before [19, 22] and constructed in the laboratory. The recording was photographic. The spectral slit width was 15 cm-1 at 7000 cm-1. 

Differential thermal analysis was performed with the DuPont 900 differential thermal analyzer the heating rate was usually 10°C. per minute. To determine heats of reaction, the calorimeter attachment to the Du Pont instrument was employed. Planimeter determinations of peak areas were converted to heat values by using standard calibration curves. For the infrared spectra either a Beckman IR5A instrument or a Perkin Elmer 521 spectrophotometer with a Barnes Engineering temperature-controlled chamber, maintained dry, was used. Specimens for infrared were examined, respectively, as Nujol mulls on a NaCl prism or as finely divided powders, sandwiched between two AgCl plates. For x-ray diffraction studies, the acid-soap samples were enclosed in a fine capillary. Exposures were 1.5 hours in standard Norelco equipment with Cu Ko radiation. For powder patterns the specimen-to-film distance was 57.3 mm. and, for long-spacing determinations, 156 mm. 

The infrared spectrophotometer is the principal instrument used by scientists for ihcse measurements. Most laboratory spectrophotometers are of a dispersive design, i.e.. a prism or grating is used to separate the spectral components in the source radiation. Modern infrared spectrophotometers base it wide wavelength range from 2 to 50 micrometers. They lind use in research, quality control, and analytical service laboratories. 

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