On-line sorption systems

In this alternative, the liquid eluted from the sorption system —generally a column— Is introduced directly into the analyser or instrument [8,9]- A scheme of the typical functioning of these systems is depicted in Fig. 4.13. The system operation consists of two stages. In the first, the sample is aspi- 

There are several commercially available instruments using sorption systems for sample pretreatment. A representative example of those working in a continuous fashion is the Varian AASP (Advanced Automated Sample Processor) [10]. This uses cassettes of ten sorbent cartridges, each of which is packed with 40-50 mg of a particular bonded silica gel. It features three essential differences from typical manual systems, namely the use of lower sample and solvent volumes, the utilization of pressure rather than vacuum and the fact that the liquid emerging from the cartridge is completely eluted to the HPLC system, thereby increasing the sensitivity. Analytical Biochemistry Laboratories (ABC) markets a module (GPC 1002 A) for automated clean-up of residues in extracts by use of a gel-permeation column. 

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Fig. 4.12 Automatic on-line sorption system for chemical clean-up used in the determination of TCDD in tissue samples. (Reproduced from [7] with permission of the American Chemical Society).

Fig. 4.13 Scheme of on-line sorption system for preconcentration of liquid samples prior to introduction into a liquid chromatograph. (A) Preconcentration stage (B) elution-determination stage. (Reproduced from [8] with permission of Elsevier). 

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