LimsPulse
Polarimeter · Calibration procedure

Temperature

Compares the sample cell temperature shown by the polarimeter with a calibrated reference thermometer at the working temperatures.

Photo of a Polarimeter
Photo: Gingkoaceae, CC BY-SA 4.0 (cropped), via Wikimedia Commons
PURPOSE

Why this is checked

Optical rotation changes with temperature, and monographs state the temperature (usually 20 °C or 25 °C). A wrong cell temperature gives a wrong [α] even if the angle scale is perfect.

Frequency

Typically every 6 or 12 months and after repair, as defined in your calibration SOP.

Learn how the Polarimeter works
YOU WILL NEED

Standards & tools

  • Calibrated reference thermometer or probe with traceable certificate, small enough to fit the sample tube
BEFORE YOU START

Prerequisites

  • Instrument warmed up
  • Tube filled with water or the probe fitted as the manufacturer describes
PROCEDURE

Step by step

  1. 1Set the cell temperature to 20.0 °C.
  2. 2Insert the reference probe into the tube filled with water, and place it in the instrument.
  3. 3Wait until both readings are stable (often 10–15 minutes).
  4. 4Record the instrument display and the reference reading.
  5. 5Repeat at 25.0 °C and at any other temperature you use.
RECORD

Example observation table

Set point (°C)Instrument display (°C)Reference probe (°C)Error (°C)Result
20.020.020.1−0.1Pass
25.025.024.9+0.1Pass
CALCULATION

How to calculate the result

Error = Instrument display − Reference reading
  1. At 20 °C: 20.0 − 20.1 = −0.1 °C
  2. At 25 °C: 25.0 − 24.9 = +0.1 °C
ACCEPTANCE CRITERIA

Pass if

  • Error within the limit in your SOP, commonly ±0.5 °C or tighter as the manufacturer specifies.
IF IT FAILS

What to do

  • Allow more time for stabilisation and repeat.
  • If it still fails, adjust the temperature offset (if permitted) or call service.
  • Assess optical rotation results since the last passing check.
MORE

Other Polarimeter calibrations

In LimsPulse · Calibration Management

LimsPulse schedules this calibration, records the result against limits, and blocks the instrument everywhere if it fails or goes overdue.

See how