Photometers commercial

The commercial photometer (Figure 3-1) used in gaging the thickness of steel strip accomplished comparative absorptiometry by means of two beams from the same source with a detector for each beam. This scheme is well suited to this particular application. 

The easiest way to calibrate a light scattering photometer is to use a suitable standard as a reference. Although polymer solutions and dispersions of colloidal silica have been used for this purpose, commercial photometers are equipped with opal glass reference standards. 

In 1986, Foret et al.41 described an on-line UV absorbance detector that employed a commercial photometer and optical fibers in direct contact with the outer walls of the separation capillary. The optical fibers (200 (im I.D. fused silica core) conducted the light beam perpendicularly across the migrating zones one fiber was connected to a mercury lamp to serve as the illumination source, and the other directed light to a photomultiplier tube for detection. The detector was found to be linear in the range of 10"5 to 10 3 M (r = 0.994 for 10 measurements), with detection limits of 1 X 10 5 M for picric acid (S/N = 2). 

Figure 5.19. Progress in miniaturization of spectrophotometric flowthrough cells, (a) Hellma cuvette, which fits into most commercial photometers, b) Z-cell, where A are the transparent windows B, Teflon made body C, cell house, and CH, the inlet channel, (c) A fiber optic reflectance cell for optosensing at active surfaces [848], where CH is the channel of a microconduit, R is the chemically active reflecting material, OF is the optical fiber.

The apparatus is schematically presented in Fig. 10. It can be a suitabfy modified commercial scattering photometer in which the photodetector has a facility for recording both / and AT at various angles 6. A typical ceU, in which the field can be applied perpendicular to the plane containing the incident and scattered beams, is shown in Fig. 6 d. An alternative cell with electrodes of variable angle with respect to the direction of observation is also own. Ref. (26) demonstrates how commercial photometers can be modified to give the additional sensitivity required for the electric field measurements. 

Figure 10.9 Light-scattering photometers, (a) Schematic top view showing movable photodetector. (Reprinted from Ref. 2, p. 176.) (b) Cutaway photograph of commercial light-scattering instrument, the Brice-Phoenix Universal Scattering Photometer. (Photo courtesy of the Virtis Co., Gardiner, New York.)...

Commercial Hquid sodium alumiaates are normally analyzed for total alumiaa and for sodium oxide by titration with ethylene diaminetetraacetic acid [60-00-4] (EDTA) or hydrochloric acid. Further analysis iacludes the determiaation of soluble alumiaa, soluble siHca, total iasoluble material, sodium oxide content, and carbon dioxide. Aluminum and sodium can also be determiaed by emission spectroscopy. The total iasoluble material is determiaed by weighing the ignited residue after extraction of the soluble material with sodium hydroxide. The sodium oxide content is determiaed ia a flame photometer by comparison to proper standards. Carbon dioxide is usually determiaed by the amount evolved, as ia the Underwood method. 

To summarize, interfacing may involve cards in the PC connected to the CAM, perhaps using RS-232 or standalone boxes (like a photometer) connected to the PC using GPIB or a PC plus a VXI mainframe. For our reader unfamiliar with a commercial CAM, get someone to demonstrate the system, then label the cables. The most common cause of failure is an improperly connected cable. 

Critical reviews of LS photometers, especially those which are commercially available, have been made recently enough to render all but the main points and recent develop-... 

Implementing this level of automation intelligence has been the most difficult to realize within manufacturing industries. That is, while automation controls integration of simple univariate instruments (e.g., a hlter photometer) is seamless, it is much more problematic for multivariate or spectral instruments. This is due to the tower of babble problem with various process spectroscopic instraments across process instrument manufactures. That is, the communications protocols, wavelength units and hie formats are far from standardized across spectral instruments, even within a particular class of techniques such as vibrational spectroscopy. Several information technology (IT) and automation companies have recently attempted to develop commercialized solutions to address this complex problem, but the effectiveness of these solutions has yet to be determined and reported. 

Size exclusion chromatography has been greatly enriched recently by the advent of two commercial detectors, the real-time differential viscometer (DV) and the low angle laser light scattering (LALLS) photometer. The only DV detector currently available is offered by Viscotek in Porter, TX, as the model 100. 

The extinction of a light beam or incident radiation associated with a cloud of particles basically involves a measure of a moment of the particle number-size distribution roughly proportional to the surface concentration. The extinction of a light beam is well-developed basis for semi-quantitative measurement of particles suspended in gases. Devices for these purposes, including smoke photometers, have been available commercially for many years. They may take many forms, one of which is the transmissome-ter, or opacity instrument. 

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