Scanning, rapid

A scan speed compensation calibration compensates for lag time in the system when the instrument is scanned rapidly. If only a scan speed compensation is performed (without a scanning calibration having been performed), the scan speed compensation is treated as a scanning calibration and the instrument is calibrated correctly only for scanning acquisitions over the same mass range and at the same scan speed as those used for the calibration. The scan speed recommended for the scan speed compensation is 1000 amu/s. 

Cyclic stationary-electrode voltammetry, usually called cyclic voltammetry (CV), is perhaps the most effective and versatile electroanalytical technique available for the mechanistic study of redox systems [37,39,41-44]. It enables the electrode potential to be scanned rapidly in search of redox couples. Once located, a couple can then be characterized from the potentials of peaks on the cyclic voltammogram and from changes caused by variation of the scan rate. CV is often the first experiment performed in an electrochemical study. Since cyclic voltammetry is a logical extension of stationary-electrode voltammetry (SEV), some important aspects of CV were treated in the preceding section. 

Li, A. C., Gohdes, M. A., and Shou, W. Z. (2007). N-in-one strategy for metabolite identification using a liquid chromatography/hybrid triple quadrupole linear ion trap instrument using multiple dependent product ion scans triggered with full mass scan. Rapid Commun. Mass Spectrom. 21 1421-1430. 

An impedance measurement can be made either by applying an electrical potential and monitoring the current response or, conversely, by passing current and monitoring the potential response. Several decades of frequencies can be scanned rapidly and accurately using a frequency response analyzer [4]. An alternative approach applies multiple frequencies simultaneously (white noise) and deconvolutes the response with a lock-in amplifier. The use of an... 

An Illustration is given in fig. 2.17, which concerns the adsorption of octa-decanol on graphite. A monolayer is formed with a herringbone-like structure, i.e. a real two-dimensional phase with well-defined domain boundaries. In the adsorption isotherms (not shown) this is reflected by an almost vertical ascent (see also fig. 2.28). An interesting aspect of this study is that information on the dynamics of the adsorbate is also obtainable. The adsorbed molecules can flip spontaneously between two different tilt angles and by scanning rapidly this process can be observed the arrow in fig. 2.17b marks the position of the scan when the flip occurred. From the scan rate the authors concluded that the switching time is much less than 10 s. 

Multi-wavelength detectors permit UV or UV-visible wavelength ran s to be scanned rapidly and therefore simultaneous plots at several wavelengths can be obtained and spectra of the analyte can be generated at very short time intervals during an entire chromatographic run. These detectors require a microcomputer for their operation and this allows all... 

Table I, shows the spectrometers recently developed by the authors. All are based on the principle of multichannel spectroscopy utilizing image devices as sensors (1). In these spectrometers, a spectrum is scanned rapidly electronically, typically in 10 ms. Spectral data can be readily available ina digitized form, the sensitivity of these image devices is generally better than...

The normal experimental technique is to scan rapidly through the velocity range and repeat this scan many times imtil data of the required accuracy has been accumulated. The Doppler motion is provided by an electromechanical drive system controlled by a servo -amplifier. Usually, the source is attached to the drive shaft and driven either in a saw-tooth or a triangular constant acceleration wave form. The transducer is coupled to a multichannel analyser operating in the multiscaler mode, and the servo-amplifier is controlled by the channel advance frequency. The dwell time in each channel, corresponding to a specific velocity increment, is 100 ps, and while the channel gate is open it accepts pulses from the detector. 

Unlike trapped ion spectrometers or sectors, oa-ToFs also have the advantage that they scan rapidly. This makes them ideal for carrying out accurate mass measurement with on-line separation systems such as GCs or HPLC [28]. A number of commercial instmments have been launched to do this. Accurate mass measurement requires good calibration and the stability of ToFs is such that an accurate mass can be obtained without adding calibrant. However, an electrospray system has been developed which allows stream switching between the LC effluent and a suitable calibration solution [29]. This has the advantage that the calibration sample need not be compatible with the analyte as it is being analysed independently. 

Peng, S., Edler, M., Ahhnann, N., Hoffmann, T., Franzke, J. (2005) A new interface to couple thin-layer chromatography with laser desorption/atmospheric pressure chemical ionization mass spectrometry for plate scanning. Rapid Communications in Mass Spectrometry RCM, 19, 2789-2793. 

The methods discussed for searching the literature use mainly printed materials. Modern search methods also make use of computerized databases and are discussed in Section 29.11. These are vast collections of data and bibliographic materials that can be scanned rapidly from remote computer terminals. Although computerized searching is widely available, it may not be readily accessible to undergraduate students. The following references provide excellent introductions to the literature of organic chemistry ... 

The NIR signal is delivered to the sample, which selectively absorbs and reflects or transmits the remainder to the detector. Several different detector types are available for FT-NIR spectrophotometers with advantages and disadvantages (see Table 5.1). Because FT-NIR spectrophotometers typically scan rapidly, detectors that can respond quickly are used. 

Williams, T.T.J. Perreault, H. Selective Detection of Nitrated Polycyclic Aromatic Hydrocarbons by Electrospray Ionization Mass Spectrometry and Constant Neutral Loss Scanning. Rapid Common. Mass Spectrom. 2000, 14. 1474-1481. 

The Bruker FT-IR imaging system (Bruker Optik GmbH, Ettlingen, Germany) used for the investigations described in this chapter is shown in Figure 8.3. The system consists of an IFS66/S step-scan/rapid-scan FT-IR spectrometer (left), which... 

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