The Distek Opt-Diss 405 fiber-optic UV spectrophotometer utilizes the patented Arch probes in order to acquire absorbance-data in-situ. Other fiber-optic systems use a different style probe called dip probes. The Distek Arch probes have several advantages over the dip probes, thereby ensuring better results for in-situ UV analysis:
1) With a dip probe, the UV light has to reflect through a horizontally placed prism in order to be retransmitted back to the detector. These horizontal surfaces allow either particulate matter to collect on the bottom surface of the prism, or air bubbles to be trapped underneath the top surface (shown above).
2) The profile of an Arch probe is smaller and thinner than a dip probe, so there are less hydrodynamic effects from the Arch probe as it resides in the vessel.
3) The Arch probe has a wide-range of pathlengths, from 0.25mm to 10mm. The shortest pathlength that a dip probe can be made in is 1mm.