Instruments, UV-visible

Instrumentation. UV/Visible spectra were collected on a Perkin-Elmer Lambda 4 spectrophotometer. IR spectra were collected on a Perkin-Elmer 1640 spectrophotometer. NMR spectra were taken on a Nicolet NT-200 spectrometer. Differential scanning calorimetry was run on a Perkin-Elmer DSC-4 unit, equipped with a system 4 microprocessor controller and a 3600 data station. Elemental analyses were run by the Purdue microanalysis laboratory in the Department of Chemistry at Purdue University and by Huffman Labs (Golden, CO). Lignin group analysis techniques are described in references 19-21. 

Forward biasing, of semiconductor diodes, 45-46 Fourier transform instruments, UV-visible, 259,... 

Far-infrared instrumentation development will continue and a universal instrument (UV-visible-NIR-IR-FIR) is a good possibility. The smaller, less expensive instrument will be continually improved, particularly in the grating field. Sources, detectors, electronics, etc., are continually being developed and improved. 

See also Atomic Absorption, Theory Atomic Absorption, Methods and Instrumentation Atomic Emission, Methods and Instrumentation Atomic Fluorescence, Methods and Instrumentation UV-VIsIble Absorption and Fluorescence Spectrometers. 

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. 

In one instrument, ions produced from an atmospheric-pressure ion source can be measured. If these are molecular ions, their relative molecular mass is obtained and often their elemental compositions. Fragment ions can be produced by suitable operation of an APCI inlet to obtain a full mass spectrum for each eluting substrate. The system can be used with the effluent from an LC column or with a solution from a static solution supply. When used with an LC column, any detectors generally used with the LC instrument itself can still be included, as with a UV/visible diode array detector sited in front of the mass spectrometer inlet. 

Most of the experimental information concerning copolymer microstructure has been obtained by physical methods based on modern instrumental methods. Techniques such as ultraviolet (UV), visible, and infrared (IR) spectroscopy, NMR spectroscopy, and mass spectroscopy have all been used to good advantage in this type of research. Advances in instrumentation and computer interfacing combine to make these physical methods particularly suitable to answer the question we pose With what frequency do particular sequences of repeat units occur in a copolymer. 

Electronic spectroscopy, often referred to as UV/visible spectroscopy, is a useful instrumental technique for characterising the colours of dyes and pigments. These spectra may be obtained from appropriate samples either in transmission (absorption) or reflection mode. UY/visible absorption spectra of dyes in solution, such as that illustrated in Figure 2.3, provide important information to enable relationships between the colour and the molecular structure of the dyes to be developed. 

Differential photocalorimetry (DPC) is included here since the instrument used is essentially an adaptation of DSC instrumentation. The photocalorimeter comprises a DSC instrument with a UV/visible source mounted on top, such that light of appropriate wavelength or wavelength region from the source is focused onto the measuring head (both reference and sample pans). The most frequent use of DPC is in the study of polymer cure reactions, but it may also be used to follow such as UV degradation. 

The technique is currently not used as widely as UV, visible and infrared spectrometry partly due to the high cost of instrumentation. However, it is a powerful technique for the characterization of a wide range of natural products, raw materials, intermediates and manufactured items especially if used in conjunction with other spectrometric methods. Its ability to identify major molecular structural features is useful in following synthetic routes and to help establish the nature of competitive products, especially for manufacturers of polymers, paints, organic chemicals and pharmaceuticals. An important clinical application is NMR imaging where a three-dimensional picture of the whole or parts of a patient s body can be built up through the accumulation of proton spectra recorded over many different angles. The technique involves costly instrumentation but is preferable to... 

Selecting an approach If available, a CO-Oximeter, an instrument used to test human blood by measuring its UV-Visible light spectrum, would be ideal. If unavailable, a standard UV-Vis will be used. 

Like much instrumentation working in the IR/visible/UV region of the spectrum, most modern UV/visible spectrometers are of the dual-beam type, since this eliminates fluctuations in the radiation source. The principle of this has been described in detail in Section 3.2. Radiation from the source is split into two by a beam splitter, and one beam is passed through the sample cell (as in a single beam instrument). The other beam passes through a reference cell, which is identical to the sample cell, but contains none of the analyte... 

UV/visible 190-900 Cecil Instruments CE 2292 (digital) Single High... 

UV/visible 200-750 Cecil Instruments CE 594 (microcomputer controlled) Double High... 

Fluorescence spectrometers are equivalent in their performance to singlebeam UV-visible spectrometers in that the spectra they produce are affected by solvent background and the optical characteristics of the instrument. These effects can be overcome by using software built into the Perkin-Elmer LS-5B instrument or by using application software for use with the Perkin-Elmer models 3700 and 7700 computers. 

UV, visible and near infrared PU 8620 basic instrument Optional PU 8700 scanner for colour graphics PU 8800 research applications... 

The phenomenon of fluorescence has been synonymous with ultraviolet (UV) and visible spectroscopy rather than near-infrared (near-IR) spectroscopy from the beginning of the subject. This fact is evidenced in definitive texts which also provide useful background information for this volume (see, e.g., Refs. 1-6). Consequently, our understanding of the many molecular phenomena which can be studied with fluorescence techniques, e.g., excimer formation, energy transfer, diffusion, and rotation, is based on measurements made in the UV/visible. Historically, this emphasis was undoubtedly due to the spectral response of the eye and the availability of suitable sources and detectors for the UV/visible in contrast to the lack of equivalent instrumentation for the IR. Nevertheless, there are a few notable exceptions to the prevalence of UV/visible techniques in fluorescence such as the near-IR study of chlorophyll(7) and singlet oxygen,<8) which have been ongoing for some years. 

In this chapter, we review the instrumentation presently available for studying near-IR fluorescence. This includes modern semiconductor devices such as diode lasers and photodiode detectors and also more conventional devices such as discharge lamps and photomultipliers which are traditionally more usually associated with the study of UV/visible fluorescence. Throughout the chapter emphasis will be placed on the novel red/near-IR aspects of instrumentation and we will assume that the reader has a knowledge of the basics of steady-state and time-resolved techniques to the level consistent with Volume 1 of this series. 

Instruments for studying UV-visible absorbance, i.e., spectrophotometers are available in many biomedical laboratories and most investigators are familiar with the basic components ... 

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