Flow detection

Fig. 2.6.7 General principle of time-of-flight flow detection, (a) Schematic of a set-up for TOF experiments. An object of interest is placed inside an environment optimized for encoding (field gradients not shown). As the sensor medium flows out of the analyte object, its magnetization is recorded with a second coil with a smaller volume, which is placed as close to the encoding volume as possible, (b) Generic pulse sequence used for TOF experiments. Encoding along one dimension can be done by inverting the magnetization of a slice...

Key Words Training Material, Temperature Detection, Pressure Detection, Level Detection, Flow Detection, Position Indication, Radiation Detection, Process Control... 

The signal intensity and line shape can be significantly affected in continuous-flow detection and, in the case of CE, additional broadening is produced by the electrophoretic current. The amount of time that a nucleus spends in the NMR flow cell or the residence time, t, is related to the observe volume and the applied flow rate, F,... 

An example of a causal factor chart for a relatively simple incident is shown in Figure 9-8. In this example, there are two redundant pumps, one of which is required to supply feed to a reactor downstream. The operator is requested to change-over operation from Pump A, which is running, to Pump B, which was previously shutdown. Instead of opening Pump B suction valve, the operator opens the wrong valve, causing the Reactor to trip on low flow detection. 

Figure 2.11—(a) FID detector (b) NPD detector and (c) effect of flow rate on detector signal and difference between the mass flow detector and concentration dependent detector. 1, normal situation (constant flow) 2, mass flow detection (i.e. FID) with an interruption in the flow rate (the area remains constant) 3, TCD detection with an interruption in the flow rate (the area does not represent the mass of the compound flowing through the detector). 

Umemoto [36] used external generation, followed by stopped-flow detection, to study the protonation of anthracene, anthraquinone, and benzophenone anions in dimethylformamide-water solutions using an apparatus similar to Figure 29.20c. The measured half-lives were about 1.5 min or more. In the case of anthracene, the decomposition rates agreed with those obtained from polaro-graphic measurements and the following scheme was proposed. 

De Maio, W., Hoffmann, M., Carbonara, M., Moore, R., Mutlib, A., and Talaat, R. E. (2008). Identification of drug metabolites by UPLC-MS with isotope pattern directed mass chromatograms and UPLC with radioactivity flow detection. In Proceedings of the 56th ASMS Conference on Mass Spectrometry and Allied Topics. ASMS, Denver, CO. 

Aliquat 336 TEVA-Resin "Tc determination in SI system using stopped-flow detection for nuclear waste On-line liquid scintillation 44... 

The simplest of these is continuous-flow detection, but this is usually only practical when using H or 19F NMR for detection unless isotopically enriched compounds are available. However, there are examples of HPLC-NMR studies using 2H and 31P NMR detection in the drug metabolism field. Where continuous-flow NMR detection is used for gradient elution, the NMR resonance positions of the solvent peaks shift with the changing solvent composition. For effective solvent suppression, these solvent resonance frequencies must be determined as the chromatographic run proceeds. 

The H NMR on-flow detected separation is shown in Figure 3.1. This is a contour plot with H NMR chemical shift on the horizontal axis and retention... 

In this study, the retention times of the parent compound, the TV-glucoside and the 0-malonylglucoside were identified by using 19F NMR spectroscopy and on-flow detected HPLC-NMR, with this being followed by stop-flow HPLC-NMR-MS. 

The simplest method of operation is continuous-flow detection. This mode of operation is generally only practical when using H or 19F NMR for detection... 

Magnuson, M.L., Creed, J.T. and Brockhoffl C.A. (1997) Speciation of arsenic compounds in drinking water by capillary electrophoresis with hydrodynamically modified electro-osmotic flow detected through hydride generation inductively coupled plasma mass spectrometry with a membrane gas-liquid separator./. Anal. At. Spectrom., 12, 689-695. 

Figure 9 Simple Mass Flow Detection System 14...

Figure 11 Differential Pressure Flow Detection Block Diagram 17...

Given a block diagram of a typical flow detection device, STATE the purpose of the following blocks ... 

The orifice plate is the simplest of the flowpath restrictions used in flow detection, as well as the most economical. Orifice plates are flat plates 1/16 to 1/4 inch thick. 

The inlet section decreases the area of the fluid stream, causing the velocity to increase and the pressure to decrease. The low pressure is measured in the center of the cylindrical throat since the pressure will be at its lowest value, and neither the pressure nor the velocity is changing. The recovery cone allows for the recovery of pressure such that total pressure loss is only 10% to 25%. The high pressure is measured upstream of the entrance cone. The major disadvantages of this type of flow detection are the high initial costs for installation and difficulty in installation and inspection. 

The pitot tube, illustrated in Figure 5, is another primary flow element used to produce a differential pressure for flow detection. In its simplest form, it consists of a tube with an opening at the end. The small hole in the end is positioned such that it faces the flowing fluid. The velocity of the fluid at the opening of the tube decreases to zero. This provides for the high pressure input to a differential pressure detector. A pressure tap provides the low pressure input. 

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