Microdegree polarimetric measurement of glucose concentrations for biotechnology applications

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.