Multielement arrays

G. M. Levy, A. Quaglia, R, E. Lazure, and S. W. McGeorge. Spect. Acta. 42B, 341, 1987. Describes the diode array-based spectrally segmented spectrometer for simultaneous multielement analysis. 

Solid-state metal-matrix composite processing, 16 169-173 Solid-state multielement detector arrays, 23 141... 

L. Ebdon, M. Foulkes and K. O Hanlon, Optimised simultaneous multielement analysis of environmental slurry samples by inductively coupled plasma atomic emission spectrometry using a segmented array charge-coupled device detector. Anal. Chim. Acta, 311, 1995, 123-134. 

The first detectors to be used in OMA systems were standard TV image tubes. These were silicon vidicons or the more sensitive Silicon Intensified Target (SIT) detectors, which both employed silicon targets to convert optical information into electronic form. More recently, the use of solid state detectors in the form of a diode array (Reticon) has been found to have some advantages over the vidicons and SIT tubes. Current developments in the field of charge coupled devices (CCD) will probably soon provide an even better multielement detector for use in OMA systems. 

The most common detector for AES is the photomultiplier tube (see p. 174). An alternative approach for the detection of multielement (multiwavelength) information is the charged-coupled device (CCD). A CCD is essentially an array of closely spaced metal-insulator emiconductor diodes formed on a wafer of semiconductor material. Incident light striking the CCD is converted into an electrical signal. 

In a system for coherent forward scattering, the radiation of a primary source is led through the atom reservoir (a flame or a furnace), across which a magnetic field is applied. When the atom reservoir is placed between crossed polarizers scattered signals for the atomic species occur on a zero-background. When a line source such as a hollow cathode lamp or a laser is used, determinations of the respective elements can be performed. In the case of a continuous source, such as a xenon lamp, and a multichannel spectrometer simultaneous multielement determinations can also be performed. The method is known as coherent forward scattering atomic spectrometry [309, 310]. This approach has become particularly interesting since flexible multichannel diode array spectrometers have became available. 

Dynamic ranges of 3 to 6 orders of magnitude for simultaneous multielement analysis can be attained on performing AAS with a continuum source using a diode array UVV detector LOD 2 pgL 1 for the 328 nm Ag absorption line50. 

A sensor array may be a set of sensors with different sensitivities and limited selectivities. Multielement sensor arrays can provide multiple data points per sample and can discriminate against interferences. The pattern of response, which is distinct for different agents, can be used to identify an unknown component using... 

The piezoceramics can be fabricated in a number of ways to perform B-mode imaging. In its simplest form, the B-mode transducer is a circular single-element transducer with a fixed geometric focus. To a large degree this type of a transducer has been replaced today by more sophisticated multielement transducers however, there are still commercial systems where single-element transducers are used. The next more complicated designs are annular arrays, which are also circular but. 

The optical detection systems used in MIPs are the same as those used for other atomic spectrometers and can be either single or multichannel. Fourier transform-based spectrometers have also been used. Conventional optical systems are best designed if the plasma is viewed from the exit of the discharge tube, as is possible with the TMqio type cavity, rather than through the walls of the discharge tube, which become etched. The commercially available AED uses a computer-controlled silicon photodiode array detector which has multielement detection capability over segments of spectra. In recent years, MIP sources have also been investigated as ion sources for mass spectrometry. 

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