Selection of the Wavelength

Gives detailed experimental information about the selection of the wavelength and the calculations for the determination of the amount of iodine that should be used. 

Furthermore, as discussed above (see section 3.6), the easy selection of the wavelength is only feasible when using a synchrotron x-ray source. 

Marsili, N.R., Sobrero, M.S., and Goicoechea, H.C. 2003. Spectrophotometric determination of sorbic and benzoic acids in fruit juices by a net analyte signal-based method with selection of the wavelength range to avoid non-modelled interferences. Analytical and Bioanalytical Chemistry 376 126-133. 

In the case of relative measurements, the selection of the wavelength is very crucial, since the reference values of are frequency dependent. Traditionally BK-7 glass has been used as reference material for THG. Heflin, Cai and Garito [58] report a value THG of = 5.8 x lO csu at frequency A = 1910nm. If one intends to measure of a liquid solution, chloroform is a more convenient reference. However, for liquid samples, the contribution of the container windows to x has to be taken into account. Kajzar and Messier report the following values of x and for fused silica (window material) and chloroform (reference material) at frequency A = 1064nm [59] ... 

Because THG only measures the electronic contribution to the pulse width it is not as relevant as in other type of experiments. Usually a Q-switched pulsed Nd + Yag laser with nanosecond pulses is used, at low repetition rate (10-30 Hz). The selection of the wavelength is important in THG, especially when organic materials have to be characterized since organic materials generally absorb in the UV spectral range. For this reason, the fundamental output of the Nd + Yag laser is usually shifted to a longer wavelength. 

The detailed, slow photolysis of azides by UV- or X-irradiation is described in Chapter 7, Volume 1. Direct ignition or initiation of azides by light flashes has normally been interpreted in terms of a thermal mechanism, perhaps preceded by a photochemical step. More sophisticated approaches involving the careful selection of the wavelength and the application of an electric field are described in Chapter 9, Volume 1. These indicate much lower thresholds for ignition than those predicated on a thermal mechanism. 

Dispersive Instruments. In dispersive instruments monochromators are employed for selection of the wavelength. When a line-like radiation source is employed, a monochromator of low resolution is adequate, but for a continuum radiation source a high resolution monochromator is required. In dispersive equipment the exit slit width is narrower than that in non-dispersive equipment. In this way, thermal background emission and stray light originating from the atomizer can be considerably decreased, but at the same time the optical transmission also decreases. The schematic construction of a dispersive AFS instrument is shown in Figure 144. 

Similar to STXM, the selection of the wavelength of the x-ray light can be used to gain element-specific information or to optimize the contrast between different components in a multiphase system. In addition to absorption mapping, the acquisition of phase contrast images has been established, for example, based on grating interferometry [28]. 

Wavelength selection was one of the most difficult conundrums to solve during the days when MLR was the only method for calibration model development. PLS regression was heralded as the answer to this question. But PLS uses variance in the same wavelength areas as MLR (107), and selection of the wavelength range most suitable for the task in hand is stiU essential to reliable model development. The results... 

In this chapter we describe the three most important types of optical spectroscopy ultraviolet (UV) and visible, fluorescence, and infrared. UV and visible spectra can be obtained through the same spectrometer. They differ only in the selection of the wavelength of the incident light UV at 180-400 nm and visible at 400-760 nm. Both UV (and visible) and fluorescence spectra describe the phenomenon of electron excitation namely, a valence electron of a molecule is... 

A unique stopped-FIA system for simultaneous synchronous spectrofluorometric online dissolution monitoring of multicomponent solid preparations that makes use of a fiberoptic sensor was presented by Li et al. [3]. A new means of in vitro therapeutic drug monitoring was developed by hyphenating the fiberoptic sensor technique and a chemometric method. An artificial neural network method was applied to construct the mathematical model for the simultaneous analysis of the mixture of vitamins Bj, B2, and Bg by synchronous spectrofluorometry. The selection of the wavelength interval, the pFI of the carrier solution, and other experimental conditions were evaluated. The proposed method has been applied to the dissolution monitoring of vitamin B tablets with satisfactory results. The recovery was 97.8%-105%, and the relative standard deviation (RSD) was 1.1-7.5. 

A poly crystalline sample of the optically pure monomer (I) was irradiated at 5°. There were formed dimers, trimers, and CHCI3-soluble and -insoluble polymers. Some isomerization about the OC(CN)COOEt double bond also occurred. By suitable selection of the wavelength of the exciting light it was possible to maximize the yields of dimers and trimers, which could then be separated from other products. 

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