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 50C. Temperature biases of 14 to 22C 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.
Abstract. Thermal/optical methods have been widely usedfor quantifying total carbon (TC), organic carbon (OC), andelemental carbon (EC) in ambient and source particulatesamples. Thermally defined carbon fractions have been usedfor source identification. Temperature precision in thermalcarbon 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 owingto different thermal properties between the sample filterpunch and the thermocouple, or inhomogeneities in the heatingzone. Quick-drying temperature-indicating liquids (TempilInc., South Plainfield, NJ) of different liquefying pointsare used as temperature calibration standards. These consistof chemicals that change their appearance at specific temperaturesand can be optically monitored to determine thesample temperature. Temperature measures were evaluatedfor three different models of carbon analyzers. Sample temperatureswere found to differ from sensor temperatures by10 to 50C. Temperature biases of 14 to 22C during thermalanalysis were found to change carbon fraction measurements.The temperature indicators allow calibration curvesto be constructed that relate the sample temperature to thetemperature measured by a thermocouple.
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