Application of Newton’s Zero Order Caustic for Analysis and Measurement: Part II Fluorescence

Abstract

An oblate spheroid-shaped liquid solution acts as a lens through the phenomenon of Newton’s zero order caustic resulting in the focusing of a low power source into high intensity light within the sample to detect and measure fluorescence. Microwatt LED sources can be used to measure fluorescence in two ways, depending on the properties of the solute. For a weakly fluorescing solute, emitted light can be detected as a beam emanating from the spheroid sample along the path of illumination. For strongly fluorescing solutes, emitted light can be detected radiating from the surface orthogonal to the excitation source. Three fluorescent molecules (tartrazine, SYBR Green I, and BBT anion) were studied using photodiode excitation sources of 430 and 470 nm maximum wavelengths respectively. Image capture for strongly fluorescent molecules was performed with a digital phone camera, followed by image analysis in order to calibrate light detected as a function of fluorescent molecule or complex concentration.