Multichannel array detector

Adaptability the possibility of outfitting with certain ionization techniques and other ancillary devices, such as multichannel array detectors and chromatographic devices. Coupling a high-resolution separation device to a mass spectrometer helps in the analysis of real-world complex mixtures of samples. 

Figure 3.32. Conceptual diagram of a multichannel array detector. (Reproduced from C. Dass, in D. M. Desiderio, ed., Mass Spectrometry Clinical and Biomedical Applications, VoL 2, by permission of Plenum Press, copyright 1994.)...

PMTs and linear PDA detectors are discussed in detail in Chapter 5. This section will cover the 2D array detectors used in arc/spark and plasma emission spectrometers. In order to take advantage of the 2D dispersion of wavelengths from an echelle spectrometer, a 2D detector is required. The detector should consist of multiple individual detectors positioned (arrayed) so that different wavelengths fall on each individual detector. Such an array detector is called a multichannel detector. 

Electron Multiplier Photo multiplier Faraday Cap Array Detectors Multichannel Plate... 

Another approach to multielemental analysis is to use a multichannel instrument that allows for the simultaneous monitoring of many analytes. A simple design for a multichannel spectrometer consists of a standard diffraction grating and 48-60 separate exit slits and detectors positioned in a semicircular array around the diffraction grating at positions corresponding to the desired wavelengths (Figure 10.50). 

An optical detector with appropriate electronics and readout. Photomultiplier tubes supply good sensitivity for wavelengths in the visible range, and Ge, Si, or other photodiodes can be used in the near infrared range. Multichannel detectors like CCD or photodiode arrays can reduce measurement times, and a streak camera or nonlinear optical techniques can be used to record ps or sub-ps transients. 

No account of UV detectors would be complete without mention of the diode array (multichannel) detector, in which polychromatic light is passed through the flow cell. The emerging radiation is diffracted by a grating and then falls on to an array of photodiodes, each photodiode receiving a different narrow-wavelength band. A microprocessor scans the array of diodes many times a... 

The main detectors used in AES today are photomultiplier tubes (PMTs), photodiode arrays (PDAs), charge-coupled devices (CCDs), and vidicons, image dissectors, and charge-injection detectors (CIDs). An innovative CCD detector for AES has been described [147]. New developments are the array detector AES. With modem multichannel echelle spectral analysers it is possible to analyse any luminous event (flash, spark, laser-induced plasma, discharge) instantly. Considering the complexity of emission spectra, the importance of spectral resolution cannot be overemphasised. Table 8.25 shows some typical spectral emission lines of some common elements. Atomic plasma emission sources can act as chromatographic detectors, e.g. GC-AED (see Chapter 4). 

Topics which will be presented in this chapter include the hardware, software, automation, valve and column configurations, and integration used in comprehensive 2DLC. Aspects of the 2DLC experiment in conjunction with multichannel detectors such as UV diode array optical detectors and mass spectrometers are discussed along with the handling of the data, which is expected to expand in scope in the future as chemometric methods are more widely used for data analysis. 

The multichannel coulometric detection system serves as a highly sensitive tool for the characterization of antioxidant phenolic compounds because they are electroactive substances that usually oxidize at low potential. The coulometric efficiency of each element of the array allows a complete voltammetric resolution of analytes as a function of their oxidation potential. Some of the peaks may be resolved by the detector even if they coelute (Floridi and others 2003). 

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