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Understanding Polarimeter Temperature Correction

Overview

Temperature Correction allows the user to select the type of temperature correction applied when making measurements.

A temperature-corrected measurement mathematically compensates for changes in optical rotation caused by differences between the sample temperature and a reference temperature. The AutoPol uses 20°C as the reference temperature.

When temperature correction is enabled, the measured optical rotation is corrected to the value expected at the 20°C reference temperature based on the selected temperature coefficient.

Temperature Correction Formula

AutoPol temperature correction is applied to the directly measured Observed Rotation (°Arc) using a linear temperature correction equation:

αTr = αT [1 − Co(T − Tr)]

Where:

  • αTr = Optical rotation (°Arc) corrected to the reference temperature, Tr
  • αT = Uncorrected optical rotation (°Arc) measured at sample temperature T
  • Co = Temperature coefficient of the sample
  • T = Sample temperature (°C)
  • Tr = Reference temperature (°C); AutoPol uses 20°C

 

Temperature Correction Options

The Temperature Correction menu provides three options: Off, Quartz, and Sucrose.

Off:  Disables temperature correction. The displayed result is not corrected for sample temperature.

Quartz:  Applies the temperature correction coefficient for quartz.

AutoPol uses the following equation:

α20 = αT [1 − 0.000143(TQ − 20)]

Where:

  • α20 = Optical rotation (°Arc) of the quartz sample corrected to 20°C
  • αT = Uncorrected optical rotation (°Arc) of the quartz sample
  • TQ = Temperature of the quartz sample (°C)

Sucrose:  Applies the temperature correction coefficient for sucrose.

AutoPol uses the following equation:

α20 = αT [1 + 0.000155(TS − 20)]

Where:

  • α20 = Optical rotation (°Arc) of the sucrose sample corrected to 20°C
  • αT = Uncorrected optical rotation (°Arc) of the sucrose sample
  • TS = Temperature of the sucrose sample (°C)

Important Note

Temperature correction is applied to the directly measured Observed Rotation (°Arc). Any additional calculated or displayed measurement scales are derived from the temperature-corrected observed rotation when temperature correction is enabled.