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 Beekman Instruments Optima XL-A Analytical Ultracentrifuge. A thermochromic solution of CoCl2 . 6H(2)0 was used as the temperature sensing material. The dehydration of CoCl2 . 6H(2)O is temperature dependent resulting a highly temperature dependent absorption peak at 660 nm. Spectra of 0.1 M CoC1(2) . 6H(2)O in an alcohol-water mixture were measured at different temperature settings of the XL-A. The spectra of the same CoC1(2) 6H(2)O 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. (C) 1995 Academic Press, Inc.