Spark discharge detector

Spark. The chief characteristic of the spark discharge is its dependence upon short times and short-time processes. In routine use, the spark signal is time-integrated by a photographic emulsion or by the electronics associated with photoelectric detectors. The spark is typically produced by the discharge of a capacitor between the sample and counter electrodes Figure 11.5 is a simplified circuit diagram of 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). 

A related type of detector uses a spark to generate high energy photons that produce sample ionization. This detector is called a discharge ionization detector (DID). It finds application in the analysis of fixed gases at lower levels than can be determined with a TCD. 

Currently, the primary use of spark source emission spectroscopy is for the identification and analysis of metals and other conducting materials. Detection is often carried out with a polychromator equipped with photomultiplier tubes, but a number of vendors offer spectrometers with array detectors as well. In addition, several modern multichannel instruments arc now equipped with interchangeable sources that permit excitation by plasmas, arcs, sparks, glow discharge, and lasers. High-voltage sparks have also become... 

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