Page 183 - Tandem Techniques

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developed, e.g the jet concentrator invented by Ryhage [2], and the helium diffuser developed by
Bieman [3] later known as the Bieman concentrator.

The Ryhage Concentrator

A diagram of the Ryhage concentrator is shown in Figure 5.1. The concentrator consists of a succession
of jets that are aligned in series but separated from each other by carefully adjusted gaps (usually a
double jet combination is used but sometimes three or more can be employed). Each subsequent jet has
a smaller aperture than the previous one. The helium passes through the center channel and diffuses
away in the gaps between the jets. The helium that has left the main stream is removed by appropriate
vacuum pumps (usually one for each jet). In contrast, the solute vapor, having greater momentum,
continues into the next jet and finally into the mass spectrometer.

Figure 5.1
The Ryhage Concentrator
Despite first impressions to the contrary, the device proved to be very effective. The concentration
factor is a little greater than an order of magnitude depending on the jet arrangement. Perhaps even
more surprising, the sample recovery is usually well in excess of 25%. This