Refining temperature measures in thermal/optical carbon analysis J. C. Chow1, J. G. Watson1, L.-W. A. Chen1, G. Paredes-Miranda1, M.-C. O. Chang1, D. Trimble1, K. K. Fung2, H. Zhang3, and J. Zhen Yu3 1Division of Atmospheric Sciences, Desert Research Institute, 2215 Raggio Parkway, Reno, NV 89512, USA 2Atmoslytic Inc., 24801 Alexandra Ct., Calabasas, CA 91302, USA 3Department of Chemistry, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China
Abstract. Thermal/optical methods have been widely used for quantifying total carbon
(TC), organic carbon (OC), and elemental carbon (EC) in ambient and source
particulate samples. Thermally defined carbon fractions have been used for
source identification. Temperature precision in thermal carbon analysis is
critical to the allocation of carbon fractions. The sample temperature is
determined by a thermocouple, which is usually located in the oven near the
sample. Sample and thermocouple temperature may differ owing to different
thermal properties between the sample filter punch and the thermocouple, or
inhomogeneities in the heating zone. Quick-drying temperature-indicating
liquids (Tempil Inc., South Plainfield, NJ) of different liquefying points
are used as temperature calibration standards. These consist of chemicals
that change their appearance at specific temperatures and can be optically
monitored to determine the sample temperature. Temperature measures were
evaluated for three different models of carbon analyzers. Sample
temperatures were found to differ from sensor temperatures by 10 to 50°C.
Temperature biases of 14 to 22°C during thermal analysis were found
to change carbon fraction measurements. The temperature indicators allow
calibration curves to be constructed that relate the sample temperature to
the temperature measured by a thermocouple.
Citation: Chow, J. C., Watson, J. G., Chen, L.-W. A., Paredes-Miranda, G., Chang, M.-C. O., Trimble, D., Fung, K. K., Zhang, H., and Zhen Yu, J.: Refining temperature measures in thermal/optical carbon analysis, Atmos. Chem. Phys., 5, 2961-2972, doi:10.5194/acp-5-2961-2005, 2005.