A fluorescence sensing technique that relies on the human eye to determine polarization can detect submicromolar concentration of rhodamine 800 and indocyanine green, dyes that could be used for monitoring drugs in patients with chronic diseases. Developed by scientists at the Center for Fluorescence Spectroscopy at the University of Maryland School of Medicine, the technology was detailed in the April 1 issue of Analytical Chemistry. But to our knowledge, no such device has been used up to now. Our goal was to develop a simple method, easy to use by any individual, and relatively inexpensive. The idea is indeed a simple one.
Incident light fluoresces a transparent reference material, and the fluorescent light is polarized.
The transmitted incident light then fluoresces the sample, whose fluorescent light is not polarized. Next, a filter removes the incident light and selects the wavelengths needed for analysis. Light then passes through a dual polarizer, half polarized vertically and half horizontally. The eye views the light through an adjustable polarizer, which is rotated until both sides of view are of equal brightness. The angle of rotation is related by a calibration curve to the concentration of the analyte.