Microdegree polarimetric measurement of glucose concentrations for biotechnology applications

Abstract

It has long been known that certain organic molecules in solution, e.g. glucose, possess the property of optical activity, rotating the E vector of linearly-polarized light passed through the solution. A Gilham-based polarimeter uses crossed polarizers and E vector modulation to measure the amount of rotation of polarized light caused by a solution of a known path length. In the past, such systems have required the use of an expensive Faraday rotator and a high-voltage photomultiplier tube (PMT) to obtain resolutions down to the microdegree range. We have developed a modified low-cost Gilham polarimeter with microdegree resolution using a coil wound around the solution-under-test instead of a Faraday rotator, and a silicon photo-diode instead of a PMT.