Photo ionisation detector

As GC techniques became more refined and were generally accepted, due to the superior separation and resolution potential of modern capillary columns, they took preference, especially in the analysis of PAH in car exhaust emissions and air particulates. In combination with an FID-detector, which, in contrast to the UV-detectors used frequently in HPLC analysis, has a nearly uniform response factor for hydrocarbons, or coupled to mass spectrometry, this technique must now be considered the method of first choice for a reliable and reproducible determination of PAH traces in a wide range of matrices. The introduction of more sensitive (photo-ionisation detector - PID) and specific detectors, such as the nitrogen-phosphorus (NPD)... 

Lanthanum hexaboride (LaBe) thin films exposed to air show reasonable work function values that makes them suitable for photoelectron applications that finally may employ LED instead of discharge lamps. Various thin films are investigated and compared with ceramic references. The low work function values associated with a moderate surface reoxidation of the films which, of course sets some limits for thin film processing in MEMS systems. As an example for the apphcations feasible a nano ioniser suitable for ambient conditions is presented, which exceeds the actual physical limits and parameterisation of conventional photo ionisation detectors. 

Keen visual observation is the most important task during a site reconnaissance. Flowever, some basic in-held chemical testing equipment is useful. Commercial kits are available, mainly based on colorimetric reactions. These kits can be used to check for the presence or absence of common contaminants and to measure soil pH. However, the results obtained using these test kits should only be regarded as qualitative, not least because samples taken at the surface may not represent the bulk of materials on the site. For site reconnaissance, the use of in-held instrumental testing is not justihed. An exception is hand-held equipment to test for the presence of gaseous and volatile contamination—photo-ionisation and other detectors are useful where such contaminants are anticipated. While a Phase la study does not normally include intrusive investigation, a small number of samples may be taken for laboratory analysis. These can be important when waste and other potentially contaminated materials of unknown composition have been spread, deposited or are stored on the site. 

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