The micropreparative technique
The enrichment procedure is based on a repetitive adsorption of eluting compounds, after separation from a capillary column, by sucking them trough an adsorption tube mounted on the outlet splitter. Optimisation is easily performed during a supervised GC run in a semi automatic mode. Repetitive sample processing becomes possible today with the aid of computers. Using simple logical decisions, they are able to reliable supervise even complex systems. Based on the FID signal of a reference substance the system directs the column effluent at any given time (using the time events table of any Data Handling System) into the collecting system where the individual compounds of interest are adsorbed.
Principle of operation
The samples to be separated are filled into standard Autosampler Vials which are placed into a Automatic Sampler. The sample will be injected using the On-Column or splitless technique on conditioned 0.32 mm i.d. capillary columns.
Small glass tubes filled with an adsorbent are used for sample enrichment. They are placed on a special designed revolving carousel located at the end of the transfer line.
The column it connected to a Press-Fit, one branch going to the detector (FID), the other to the Prep. During normal run conditions the whole column effluent flows into the detector. On collection the effluent is directed through the adsorption tubes. This is accomplished by the following mechanism:
The other side of the adsorption tube placed at the end of the splitter branch is connected to vacuum circuit and isolated by a solenoid valve. The vacuum is activated by switching a solenoid valve opening the circuit to the vacuum pump. On collection the valve is opened, the whole effluent passed through the adsorption tube, so efficiently that the signal of the FID become negative. During normal operation (no collection) the solenoid valve is closed. Thus a standing gas volume, serving as a gas barrier, is obtained in the splitter branch leading the adsorption tube. Therefore, the column effluent is forced to flow through the splitter branch leading to the FID and does not contaminate the adsorption tube.
The Prep 9000 comes with Prep recovery software. This software helps you prredict the number of collection needed to achieve a specific amount as well as a the recovery factor of the overall process.
Simple to use, flexible, straight forward, it is a great tool for optimizing the collections.