Thermistor bead element

Thermistor bead element. A thermal conductivity detection device in which a small glass-coated semiconductor sphere is used as the variable resistive element in the cell chamber. 

Thermal conductivity detectors in PGC are universal detectors in that they can be used to measure any component (Figure 2). Typically, TCDs are used to measure percent level components, but because it is a concentration-sensitive detector, the TCD can be designed for lower level analyses by optimizing the detector volume and sensing elements. TCDs used in PGC utilize either filaments or thermistor beads as their sensing elements. Filaments have the advantage that they can be operated at higher temperatures, but they are more prone to failure than are thermistors. The sensitivity is mainly dependent on the detector temperature and the thermal conductivity difference between the carrier gas and the component of interest. 

Whole cells were employed [55] as the monitoring element in which Pseudomonas capacia capable of metabolizing aromatic compounds were immobilized in Ca+2-alginate beads and their response to aromatic substances, e.g., salicylate, was monitored with an enzyme thermistor. 

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