Pulsed Discharge Detector PDD

The pulsed discharge detector (PDD) is a universal and highly sensitive nonra-dioactive and non-destructive detector, also known as a helium photoionization detector. It is based on the principle of the photoionization by radiation 

The discharge and carrier gas flow out together from the bottom of the cell where it is possible to measure the sum of both at the outlet on the back of the instrument. 

The FDD chromatograms show a great similarity to the classical FID detector and offers comparable performance without the use of a flame, radioactive emitter or combustible gases. The FDD in helium photoionization mode is an excellent replacement for FIDs in petrochemical or refinery environments, where the flame and use of hydrogen can be problematic. In addition, when the helium discharge gas is doped with a suitable noble gas, such as argon, krypton or xenon (depending on the desired cut-off point), the FDD can function as a specific photoionization detector for selective determination of aliphatics, aromatics, amines, as well as other species. 

Some FDD detectors also offer an electron capture mode being selective for monitoring high electron affinity compounds such as freons, chlorinated pesticides and other halogen compounds. For such type of compounds, the minimum detectable quantity (MDQ) is at the femtogram or low picogram level. The FDD is similar in sensitivity and response characteristics to a conventional radioactive ECD, and can be operated at temperatures up to 400 °C. For operation in this mode. He and CH are introduced just upstream from the column exit. 

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Pulsatile drug delivery systems, 9 57-61 Pulsating heat pipes (PHP), 13 235-236 Pulse combustion heat sources, 9 104-105 Pulse cycles, 9 778 Pulsed baffle reactors, 15 709-710 Pulsed discharge detector (PDD) gas chromatography, 4 614 Pulsed dye lasers, 23 144 Pulsed electrochemical machining (PECM), 9 604-605... 

Forsyth, D.S., Taylor, J. Detection of organotin, organomercury, and organolead compounds with a pulsed discharge detector (PDD). Anal. Bioanal. Chem. 374, 344-347 (2002)... 

Detection systems for GC are chosen for their sensitivity and selectivity for a particular class of VOCs. Detectors for GC include FID, the BCD, the photoionization detector (PID), the pulsed discharge detector (PDD), and the reduction gas detector (RGD). A variety of mass spectrometers can also be interfaced with a GC for confirmation of molecular structure and quantitation. Singlewavelength ultraviolet-visible detectors (190 to 600 nm) and diode array detectors are used to detect carbonyls as their 2,4-dinitrophenylhydrazone derivatives. The absorption maxima for aliphatic carbonyls, aromatic carbonyls, and dicarbonyls are near 360 nm, 385 to 390 nm, and 415 to 430 nm, respectively. Formic, acetic, and pyruvic acid are detected by ion conductivity. 

Figure 2.149 Pulsed discharge detector (PDD) in cutaway view (Thermo Scientific).

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