Improved Spectrometer for Long Path Length Absorbance



Absorbance Spectroscopy, Chemical And Analytical Lab Research Tools, Flow Injection, Gas Chromatography, Liquid Chromatography/HPLC, and Capillary Electrophoresis.

Target Problems

  • Conventional spectrometer configuration has narrow range of measurable concentrations
  • Limited path length that limits the sample range

Key Features

  • Wide Sample Concentrations – Allows for measurement of extremely dilute samples, and adjustable path length also allows for measurement of high concentration samples.
  • Low Cost – Design uses standard optics and off-the-shelf spectrometer components.
  • Flexible Design and Variable Path Length – The dove prism configuration allows for liquid flow-through spectroscopy and evanescent wave measurements of condensed phase samples.


A technology that improves the optical configuration of spectrometers for long path length absorbance measurements for gas and condensed phase. The current technology uses a compact optical cavity with a rotating mirror to control the beam path length as shown in the diagram. For example, HPLC is a technique that could benefit from this unprecedented capability in measuring a wide range of concentrations, i.e., samples containing both ultra-trace as well as relatively high levels could be measured in the same chromatographic run.

Intellectual Property


Joseph H. Aldstadt III, Ph.D.
Assoc. Prof. & Chair, Department of Chemistry- Analytical
University of Wisconsin – Milwaukee