Go with the Flow

improve sensitivity fivefold

(This is a slightly revised version of the article which appeared in the print edition of The Scientist)

The LightPipe Flowcell from ThermoQuest is one of the critical components of the company's new UV6000LP Photodiode Array Detector. The flowcell resolves a longstanding problem in optoelectric devices: When the pathlength of a conventional flowcell is increased, both the signal and the background noise are increased in a relationship expressed by the Lambert-Beer law (A=ebc). The basic design for dealing with this problem has been to develop a slit aperture that decreases the signal to the photodiode array while increasing stray light noise. This has the effect of essentially cropping the incoming beam of light before it has a chance to get picked up by the array. Although this technique has been applied successfully in a...