Operation and Calibration of Polarimeter

  1. Objective

To lay down a procedure for operating and calibration of Polarimeter. It is used to determine the optical rotation of material.

  • Scope

This SOP is applicable for operation and calibration of Polarimeter (Make: Rajdhani, Model RSP-3)  in Quality Control.  

  • Responsibility

QC Chemist / Officer : Follow the procedure and maintain record as applicable.   

  • Accountability

Head Quality Control  : System Compliance

  • Procedure:  
    • Operation:
      • Ensure that equipment & tube is clean.
      • Check the calibration due date.
      • Set up the instrument on the bench with the analyzer head facing the operator, an illuminated sodium lamp is attached with equipment through a bracket.
      • Switch ON the mains.
      • Switch ON the Sodium vapour lamp by pushing the switch of transformer downward. The red indicator will glow on transformer.
      • Wait for five minutes so that Sodium vapour lamp gets illuminated completely.
      • The position of Sodium vapour lamp is such that the field can be seen clearly while viewing through lower eyepiece.
      • Adjust the lower & upper eye piece & focus it by sliding it towards your eye or away from your eye to view the clearly.
      • After focusing the upper eye piece you will see the scale graduation & a vertical line called reference line.
      • Rinse the tube with the solvent used and fill the tube with the solvent in such a manner that there should not be any air bubble.
      • Place the tube in the cabinet and close it.
      • Now see through the lower eye piece and match the colour shade to similar in both section by rotating the knob placed on the opposite to eye piece.
      • Take the reading by viewing through upper eye piece.
      • If the reference line do not concide with the scale then adjust with micrometer drum knob.
      • Take the five readings.
      • Now rinse the tube with the solution and fill the tube with the liquid / prescribed solution and take reading following the procedure given above.
      • Take the reading in + or  -.
      • Deduct the reading of solvent from reading of liquid/sample and calculate the specific optical rotation.
      • After completion of work open the cabinet, remove the tube and  clean it thoroughly.
      • Switch off the Sodium vapor lamp.
      • Enter the details in Instrument log. 
    • Calibration:
      • Operate the equipment.
      • Weight accurately 50 g sucrose (previously dried) and transfer in 100 ml volumetric flask. Add 50 ml water (milli Q), shake well to dissolve and make up the volume with water (milli Q) (solution A).
      • Rinse the tube (1-dm) with water (milli Q) and filled the tube with water (milli Q) after maintaining the temperature 25 ±1ºC.
      • Set the null point with the help of knob adjustment and note the reading up to two decimal place with the help of linear and outer side.
      • Rinse the tube with sucrose solution (A) and follow the steps and measure the angle of rotation.
      • Similarly prepare solution of 40, 30, 20 and 10g/ 100 ml by diluting 20.0 ml, 15.0 ml, 10.0 ml, and 5.0 ml of solution (A) to 25.0 ml with water (milli Q).
      • Measure the angle of rotation following steps 5.4 & 5.5 and record the observation Annexure I.
      • Take average of five readings for each concentration.
      • Acceptance criteria:

Concentration (g/100ml)                  Angle of rotation (+) at 25ºC

10                                                        6.66° ± 0.5

20                                                        13.30°± 0.5

30                                                        19.93° ± 0.5

40                                                        26.53°± 0.5

50                                                        33.11° ± 0.5

  • Enter the details in Annexure I.
    • Prepare the calibration tag and affix it on the equipment.
    • Enclose the old calibration tag with the record and don’t throw it.  
    • If the variation is not within the specified tolerance limits:
      • Label the equipment with a tag, “OUT OF CALIBRATION”.
      • Inform the Department Head.
      • Do not use equipment until all errors are rectified. After rectification, again calibrate the equipment & record the observation.
      • Frequency: 6 Months ± 3 days.
    • Important:
      • Fill the tube in such a manner that there should not be any air bubble.
      • The temperature of solvent / solution should be 25°C ±1°C.
      • Ensure that the solution is clear.
      • Take five readings for each operation.
      • For any deviation in equipment inform to service engineer.
      • For more details refer instruction manual.
  • Annexure(s)


  • Reference(s)

Manufacturer manual

Chapter No. 2.4.22 of IP 2014

  • Glossary           

SOP                :  Standard Operating Procedure

QC                  :  Quality Control

QA                   :  Quality Assurance

°C                    : Degree Centigrade

g                      : Gram

ml                    : Milliliter         

  • Revision History
Rev. No. Details of changes Reason for change

Bhanu Pratap Singh


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