High temperature differential refractometry apparatus

Abstract

A differential refractometry apparatus that maintains optimal optical alignment of components while accurately providing differential refractometry measurements at elevated temperatures. The differential refractometry apparatus has a first thermal zone, a thermal isolation zone and a second thermal zone. The first thermal zone is configured to be located in an oven and exposed to higher temperatures. The thermal isolation zone is located adjacent to the first thermal zone and acts as a barrier to the conduction of heat from the first thermal zone into the second thermal zone. The second thermal zone is at a relatively lower temperature than the first thermal zone and its temperature is regulated using a thermal electric cooler located at its base. A flow cell, a mirror which reflects the incoming light beam, and an imaging lens are located in the first thermal zone. An LED and a photodiode detector are located in the second thermal zone and are encased in thermally stable blocks with low coefficients of thermal expansion. The LED sends a light beam up through the thermal isolation zone and into the first thermal zone. The light beam passes through the sample and gets reflected by the mirror. The light beam passes through the sample a second time. The light beam then passes through an imaging lens before traveling back to the photodiode in the second thermal zone. In this manner the optimal optical geometry is preserved while allowing analyses to be conducted with the sample at elevated temperatures.