Single point detectors

In general, single-point detectors, such as the catalytic, infrared, solid-state, and electrochemical types, can be put in locations up to 3,000 feet from the control room.14 Sampling systems are more limited because of the length of the tubing needed to bring the sample to the detector. 

Both homodyne and heterodyne detection can use normal detectors with subsequent electronic mixers [82, 83]. Alternatively, mixing can be performed directly in the detector by modulating its gain [73, 470]. Frequency-domain techniques with single-point detectors make frill use of the depth resolution capability of confocal and two-photon imaging but do not work well at extremely high scan rates. 

Since general purpose CE instruments are only equipped with a single point on-column detector, which is usually located close to one end of the capillary column as shown in Figure 19.1c, these stationary protein zones within the column have to be mobilized past the detection point of the single point detector. For cIEF performed on these CE instruments (conventional cIEF), a mobilization process is necessary following the focusing process [10,11]. There are three ways of performing the mobilization pressure-driven mobilization [11], salt mobilization [3], and EOF-driven mobilization [12]. These three methods can be used in any combination. 

In order to explore if the shear in the mini-Couette cell was in fact affecting phase transitions we made a twin cell compatible with SXRD and designed to fit the motor assembly used for prototype I. We modified the shaft, replacing its bottom part with Lexan of same dimensions as the Teflon shaft. The temperature control was the same used for the NMR modified probe. The cell was successfully tested at the ExxonMobil beamline XIOA of the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory (Upton, NY). The x-ray beam was sent perpendicular to the cell and the diffraction pattern was captured with a single point detector moving in the 20 angle. 

In order to measure the 3D velocity distributions, ideally one would like to have a 3D spherical TOF detector. However, commonly, TOF devices for atomic and molecular ion (or electron) analysis are ID single-point detectors. This means that the charged particle is transported from the (point) location, where it was generated, through a drift tube to... 

Figure 2.8 Infrared signal intensity recorded using a confocal IR microscope with a single-point detector through various apertures using a synchrotron or globar source. Copyright 2005, with permission from Elsevier.

Infrared signal measured through various aperture sizes using a synchrotron source versus a Globar source. Data collected with a confocal IR microscope and a single-point detector. (Reprinted from ref. 72.)... 

EELS, as early systems had a single point detector, requiring the spectrum to be scanned. In any case, scanning the spot or line over the sample can form a 3D image in x, y and energy, which is usually called a spectrum image. 

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