An optical thermometer for direct measurement of cell temperature in the Beckman instruments XL-A analytical ultracentrifuge.

An optical thermometer has been evaluated for use in the Beckman Instruments Optima XL-A Analytical Ultracentrifuge. A thermochromic solution of CoCl2.6H2O was used as the temperature sensing material. The dehydration of CoCl2.6H2O is temperature dependent resulting a highly temperature dependent absorption peak at 660 nm. Spectra of 0.1 M CoCl2.6H2O in an alcohol-water mixture were measured at different temperature settings of the XL-A. The spectra of the same CoCl2.6H2O solutions were measured on a Beckman Instruments DU-650 spectrophotometer with a calibrated thermocouple attached to the cuvette. A standard curve was constructed by plotting the area under the spectrum from 450 to 750 nm as a function of the thermocouple temperature. Spectra were obtained on the XL-A at various temperature settings and integrated over the same range. This method allows direct comparison of the cell temperature to the value displayed on the console panel of the XL-A.