Detectors Robinson

The method relies on the ability to provide a vacuum differential across the objective aperture in the electron optical column. This is in principle possible in all SEMs, but in practice easier to achieve in some microscopes than others. Image formation requires a BSE detector rather than the more commonly used SE detector. While any backscattered electron detector can be used, the high resolution potential of the SEM can only be maintained by employing a high efficiency detector, such as the Robinson detector used here. 

J.K. Robinson, MJ. Bollinger, and J.W. Birks, Luminol/H202 chemiluminescence detector for the analysis of nitric oxide in exhaled breath. Anal. Chem. 71, 5131-5136 (1999). 

For a broadband r.f. amplifier of bandwidth Afi sending a signal to a square-law diode detector and thence to a low-frequency video amplifier of bandwidth A/j the noise power is (Dicke 1946 Robinson 1974)... 

J. K. Robinson, M. J. Bollinger, and J. W. Birks, Luminol/H202 Chemiluminescence Detector for the Analysis of NO in Exhaled Breath, Anal. Chem. 1999, 71, 5131. Many substances can be analyzed by coupling their chemistry to luminol oxidation. See, for example, O. V. Zui and J. W. Birks, Trace Analysis of Phosphorus in Water by Sorption Preconcentration and Luminol Chemiluminescence, Anal. Chem. 2000, 72, 1699. 

Compared with the ICP, other atomic spectrometric detectors are not widely coupled to HPLC. Several interfaces have been described for AAS detector. Methods include a rotating platinum spiral collection system (Ebdon et al., 1987) and a flow injection thermospray sample introduction system (Robinson and Choi, 1987). Post-column hydride generation is also popular with AAS detection as will be described later. Pedersen and Larsen (1997) used an anion-exchange column to separate selenomethionine, selenocysteine, selenite and selenate with both FAAS and ICP-MS. The detection limits for the FAAS system were lmg H1 compared with 1 fig l-1 for ICP-MS. HPLC-MIP systems have been described to an even lesser extent. These either use elaborate interfaces to overcome the problems of quenching the low-power plasma (Zhang and Carnahan, 1989) or use a modified argon/oxygen mixed gas plasma (Kollotzek et al., 1984). 

G.W. Robinson, T.A. Caughey, R.A. Auerbach and P.J, Harman, "Image Detectors in Chemistry", ACS Symposium Proceeding, June 1979, Editor, Y.Talmi... 

Robinson, J.L., Tsimidou, M. and Macrae, R. (1985) Evaluation of the mass detector for quantitative detection of triglycerides and fatty acid methyl esters. J. Chromatogr., 324, 35-51. 

Epifluorescence Microscope. The diagram shows the working of an upright epifluorescent microscope. The excitation beam (black ray) from the arc lamp passes through the excitation filter and dichroic mirror and directed toward the specimen. The return beam of emitted fluorescence wavelength (red, green and black rays) is reflected of the dichroic filter, emission filter, ocular and goes to the detector (eye or camera). Courtesy of Prof. J. Paul Robinson, Ph.D., Director of Purdue University Cytometry Laboratory, Purdue University, West Lafayette, IN, USA. 

Besides cell designs that employ metals or other electrode materials in disc shape for external reflection spectroscopy, Robinson and McCreery have successfully employed cylindrical carbon fibers of 12 pm diameter [58, 59]. The carbon fiber was illuminated with a tunable dye laser. Scattered light was collected with fiber optics and guided to a photomultiplier detector. Because no thin layer arrangement and consequently poor electrochemical cell response were involved, fast experiments on a microsecond time scale were possible. Studies of polyaniline films deposited on platinum discs have been described [60]. 

A PGAA instrument consists of a source of neutrons, a collimating beam tube to shape and direct a beam of neutrons onto a sample, a shutter to turn the beam on and off, a target assembly to position the sample reproducibly in the neutron beam, a gamma-ray detector, a beam stop to absorb the neutrons that are not absorbed by the sample, and shielding to protect the detector and personnel from neutron and gamma radiation. Each of these components will be considered in turn. The construction of a recent system illustrates clearly many of the choices involved (Robinson et al. 2009). More detailed information on the issues can be obtained in the PGAA Handbook (Molnar 2004). 

The three-phase Robinson-Mahoney reactor (a continuous gas and liquid flow) consisted of a fixed catalyst basket and a magnetic stirrer. The reactor system was automated to ensure reliable and reproducible experiments. Liquid samples of the product stream were taken by an automatic on-line valve and analysed by a gas chromatograph with fused silica capillary column and FI detector. Detailed information on the apparatus [11] and the hydrogenation procedure can be found elsewhere [10]. Gas-liquid and liquid-solid mass transfer resistance were avoided by adjusting the agitation and catalyst loading. An intraparticle mass transfer resistance could not be avoided and this was added to the reactor model in parameter estimation [11]. 

The application of ICP-AES has been pioneered since 1962 by the group of Albright and Wilson (e.g., Greenfield) and by Fassel (1978). The electronic equipment, the aerosol injection and the optical systems have been steadily improved to reduce sample amounts and to lower detection limits. The recently developed semiconductor array detectors in ICP technology, in combination with a powerful data processing system, offer the advantage of simultaneous detection and calibration of 30 or more elements. For details of the physics and equipment we refer to Atkins (1987) or Robinson (1996). 

FIGURE 9.2 (a) Flow injection system used for the generation of a double-pH gradient BRH, acid Britton-Robinson solution IV, injection valve R, reactor DAD, diode array detector W, waste q, 0.56 mL/min PP, peristaltic pump, (b) Scheme of the pH gradient profile. 

Continuous wave techniques CW NQR spectrometers are based on the use of oscillator-detectors, which are built around the circuits of a marginal oscillator or a limited oscillator (Robinson oscillator). Such an oscillator-detector includes a tank circuit with a coil, into which the studied sample is inserted. When the frequency of the oscillator-detector coincides with the NQR frequency in the sample, the... 

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