Off-line sorption systems

This type of system is most commonly used in the collection and preconcentration of toxic substances from the atmosphere by means of withdrawal pumps fitted to small columns located at strategic points and connected to an automatic programmed thermal desorption instrument coupied to a gas chromatograph. A detailed description of these systems is given in Chapter 12. 

Lapeza et al. [7] recently reported an automatic system (Fig. 4.12) for pretreatment (sorption and preconcentration) of 2,3,7,8-tetrachlorodlbenzo-p-dioxln in human adipose tissue for Its subsequent determination at the parts per 101 level by hlgh-resolutlon gas chromatography-mass spectrometry. The microprocessor used allows the control of the functioning of the pump and a series of valves (a six-position rotary, a four-way rotary and a tandem six- 

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