Election capture detector

The 2-bromoethanol produced in this reaction is analysed by gas chromatography using an election capture detector. At the 10 mg/kg level in soil a standard deviation of 0.34 mg/kg was obtained, i.e., a coefficient of variation of 3%. Recoveries from soil were 81-94%. 

The selectivity of the election capture detector, coupled with its extreme sensitivity (down to 1 pg), makes it very useful for compounds such as tiie benzodiazepines or halogenated pesticides. Alternatively, the great sensitivity of the detector may be utilised by preparing derivatives with reagents such as heptafluorobutjric anhyctiide. For some compounds the sensitivity of tiiis detector may exceed that of the mass spectrometer. 

A study to explore the effect of the sample matrix in SFE was done with a set of polychlorinated biphenyl (PCBs) and a river sediment matrix. Figure 12 shows the on-line SFE/GC characterization of a PCB standard ranging from monochloro to decachlorolbiphenyl compounds present at concentration levels from 5 to 100 microgram per milliliter. An election capture GC detector (ECD) was used for the determination of these PCB s. Since this PCB standard was made up in liquid... 

Ar. Ns This detector employs a source of P radiation (usually 6JNi-cf. helium ionisation detector). The 1000-10.000 velocities of the high energy electrons are reduced to thermal velocities by coOisioo with atoms of inert gas with which the detector chamber is purged. When a sample of a gas with a greater election affinity than the inert gas is introduced into the ccC some of the electrons are captured and form negative ioas. 

---