Detectors typical characteristics

To preserve the good background characteristics of the detectors (typically about 0.4 count/1000 min in the 239,24op qj. region),... 

An evaluation of gas chromatographic detectors typically involves a study of dynamic range, mimimum detectable level and selectivity. Dynamic range is one of the major response characteristics of detectors. It is the range of sample... 

The most common selective detectors in use generally respond to the presence of a characteristic element or group in the eluted compound. This is well illustrated by the thermionic ionisation detector (TID) which is essentially a flame ionisation detector giving a selective response to phosphorus- and/or nitrogen-containing compounds. Typically the TID contains an electrically heated rubidium silicate bead situated a few millimetres above the detector jet tip and below the collector electrode. The temperature of the bead is maintained... 

In summary, the NFS investigation of FC/DBP reveals three temperature ranges in which the detector molecule FC exhibits different relaxation behavior. Up to 150 K, it follows harmonic Debye relaxation ( exp(—t/x) ). Such a distribution of relaxation times is characteristic of the glassy state. The broader the distribution of relaxation times x, the smaller will be. In the present case, takes values close to 0.5 [31] which is typical of polymers and many molecular glasses. Above the glass-to-liquid transition at = 202 K, the msd of iron becomes so large that the/factor drops practically to zero. 

Principles and Characteristics The main reasons for hyphenating MS to CE are the almost universal nature of the detector, its sensitivity and the structural information obtainable, including assessment of peak purity and identity. As CE is a liquid-phase separation technique, coupling to the mass spectrometer can be achieved by means of (modified) LC-MS interfaces. Because of the low flow-rates applied in CE, i.e. typically below lOOnLmin-1, a special coupling device is required to couple CE and the LC-MS interface. Three such devices have been developed, namely a... 

Energy-dispersive spectrometry (EDS) is a technique of X-ray spectroscopy that is based on the simultaneous collection and energy dispersion of characteristic X-rays. Typical ED detectors are thermoelectrically cooled semiconductors (usually operated at 77 K), PIN diodes,... 

The instruments used in X-ray emission spectrometry reflect the principles set out in Chapter 7. Radiation characteristic of the specimen is produced by electron or radiation bombardment. Monochromatic radiation is then presented to the detector by a diffraction device or by use of a series of narrow bandpass filters. Alternatively pulse height analysis (p. 465) can be applied to a series of pulses which have been generated with a size proportional to the radiation energy. Typical X-ray spectrometry arrangements are shown in Figures 8.40 and 8.41. 

---