Spectrometer reflection

Flexible data management enables the new Reflotron system to perform the following tasks  

The aim was to achieve the same results with the Reflotron system as would have been obtained by employing a wet process. A certain concentration c of the substance to be analysed yields a certain reflection R when reacting with carrier-bound reagents. This relationship can be expressed by the functional curve 

The fundamental functional relationship between the concentration of the substance to be analysed, with respect to its formed dye on the dry reagent carrier, and the measured light reflection, can be expressed by the theory of Kubelka and Munk  

Obviously, this is mainly a mathematical description of a hyperbola, the first member of the equation being a constant, the second member a straight line and the third a hyperbola. Based on the examinations carried out, the formula was generalised as follows  

The exponential function introduced here serves as a correcting member if n 0, it equalises irregularities in the hyperbolic course, whereas for m 0 (and for Aj 0), it determines the sigmoidal course of the functional curve. 

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Fig. 1 Schematic diagram of the integrating sphere portion of a diffuse reflectance spectrometer, illustrating the key elements of the optical train. Although the detecto has been placed in the plane of the sample and reference materials, in common practice it would be mounted orthogonal to the plane created by the intersection of the optica beams.

An application of ultrasound that is becoming increasingly popular in the food industry is the determination of creaming and sedimentation profiles in emulsions and suspensions (Basaran et al., 1998). Acoustic techniques can also assess nondestructively the texture of aerated food products such as crackers and wafers. Air cells, which are critical to consumer appreciation of baked product quality, are readily probed due to their inherent compressibility (Elmehdi et al., 2003). Kulmyrzaev et al. (2000) developed an ultrasonic reflectance spectrometer to relate ultrasonic reflectance spectra to bubble characteristics of aerated foods. Experiments were carried out using foams with different bubble concentration and the results showed that ultrasonic reflectance spectrometry is sensitive to changes in bubble size and concentration of aerated foods. 

Nichols MG, Hull EL, Foster TH. Design and testing of a white-light, steady-state diffuse reflectance spectrometer for determination of optical properties of highly scattering systems. Applied Optics 1997, 36, 93-104. 

Reflectance Spectroscopy. Spectra were taken from 600 -2500 nm using a Mark II 6250 Diffuse Reflectance Spectrometer obtained from Pacific Scientific. This... 

The Infrared spectra were recorded with a specially constructed evacuable infrared reflection spectrometer using conventional optics and a grating monochromator. 

Drennen, J.K. Near-Infrared Reflectance Spectrometer System and Related Sample Cell and Sample Support. US Patent 898,454, May 25, 1993. 

A reflection spectrometer (Fig. 46) is used for measuring on the moist reagent carrier the dye that has been formed. The instrument requires an Ulbricht sphere (spheric integrator) to measure the light reflected by the test area. A... 

Fig. 46. Seralyzer reflection spectrometer (cross-section) 1 microprocessor, 2 xenon flashlight, 3 detector, 4 test module, 5 keyboard, 6 reagent slide, 7 test strip, 8 Ulbricht s sphere.

Y. Ozaki, A. Mizuno, T. Hayashi, K. Tashibu, S. Maraishi, and K. Kawauchi, Nondestructive and Noninvasive Monitoring of Deoxyhemoglobin in the Vein by Use of a Near-Infrared Reflectance Spectrometer with a Fiber-Optic Probe, Appl. Spectrosc., 46(1), 180 (1992). 

Diffuse reflectance spectrometers offer a tool to examine on-line photoprocesses on diffuse reflecting substances or to control the photostability of coloured materials as pigment or car lacquer. Either the set-up using fibre optics (see Hg. 4.11) or modified thin-layer equipment (Fig. 4.25) can be used. 

The schematic setup of a diffuse reflectance spectrometer which is obtained by supplying a normal UV-VIS spectrometer with a diffuse reflectance accessory is shown in Fig. 18. The core is an integrating sphere coated with a highly reflective material that collects the scattered radiation and leads it to the detector. The light remitted by the sample is compared with that of a white standard as the reference. Zeolite layers of ca. 5 mm depth are generally sufficient to meet the condition of infinite thickness. A typical sample cell furnished with an evacuated Infrasil double window and designed for temperature control and evacuation is depicted in the lower part of Fig. 18 [32]. Other cell constructions have been reported by Klier [31] and Schoonheydt [34]. 

Fig. 18. A Schematic representation of a diffuse reflectance spectrometer. For (i) nondiffuse dispersed illumination the source at the left and the detector at the integrating sphere are used. For (ii) diffuse nondisperse illumination (in the case of fluorescent samples) a source directly attached to the sphere and the detectors on the left upper side are applied. B Temperature-regulated and evacuable diffuse reflectance sample cell according to [32]. Reprinted from [32] with permission of Academic Press, Inc...

NIR spectroscopy is an important method for rapid on-line monitoring of oil and petrol production processes. It has become an essential component in hydrocarbon processing. NIR reflection spectrometers are also used to analyze oil sand in the petroleum industry. NIR spectroscopy is used for in-situ quantification of liquid natural gas. Feed streams can also be monitored. Finally, NIR reflection spectroscopy is also used to determine pollution and contamination of oil and other petrochemical products in sand, and earth [28] (see Reference Data Table 2 on page 114/115). 

The differential reflection spectrometer (also called the differential reflectometer) measures the normalized difference between the reflectivities of two specimens (or two slightly different parts of a specimen) as a function of photon energy. Unpolarized, monochromatic light (having the possibility to vary the wavelength continuously) is alternately deflected to one or the other sample by means of a vibrating... 

Figure 12 Schematic diagram of the differential reflection spectrometer. For clarity, the angles of the incident and reflected light beams on the sample are shown larger than they are in reality,...

M. C. Pasikatan, E. Haque, J. L. Steele, C. K. Spillman, G. A. MUUken. Evaluation of a near-infrared reflectance spectrometer as a granulation sensor for first-break ground wheats Studies with six wheat classes. Cereal Chem 78 730-736, 2001. 

Table 1.4 opposes double-beam UVA IS spectrophotometry in solution to the use of a reflectance sphere (standard for industry). Recently also handheld reflection spectrometers have been introduced. 

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