• OBJECTIVE : This SOP gives the procedure of operation and calibration of polarimeter.

 

  • SCOPE : The operation and calibration of Polarimeter instrument to determine the specific optical rotation of given test sample.

 

  • RESPONSIBILITY : QC Chemist, QC officer, QC Executive, QC In charge.

 

4.0    REQUIREMENTS : Sucrose solution, Volumetric flask, Pipette, Washing bottle, Tissue paper etc,

 

5.1       PRECAUTIONS

5.1.1    Handle the instrument and polarimeter tube carefully.

5.1.2    Do not keep polar meter’s tube without cleaning after use. It should be clean after each use.

5.1.3   Keep Switch off the instrument when not in use.

5.1.4   Specific optical rotation to be measure sample should be clear.

5.1.5 Avoid air bubbles in sample tube, and if any small air bubble observed, than should be adjusted in the middle portion of the tube.

 

5.2    OPERATING PROCEDURE

5.2.1 Switch On the electric supply and within 10 minutes, the sodium lamp to glow optimally.

5.2.2 Check the polarimeter tube and its cabinet. It should be clean.

5.1.1 Position the incoming light source, polarimeter tube and cabinet in a line by rotating the revolving stand of sodium lamp.

5.1.2 For clear vision of colour shade, adjust the upper and lower eyepiece to anterior and posterior side.

5.1.3 Fill the polarimeter tube with water / blank in which the substance is dissolved and place this in cabinet. (determine at Temperature 25°C, unless & otherwise specified in the procedure/monograph)

5.1.4 Rotate the knob at the anterior right and match the colour shade in both sections by observing in lower eyepiece.

5.1.5 Take the reading in upper eyepiece, it should be about zero. Rotate the vernier scale at the left anterior head of instrument.  Add the reading of main scale and vernier scale, and find the reading of rotation.

5.1.6 Fill the polarimeter tube with the liquid / prescribed solution. Solution / liquid should be clear and free from air-bubble.

5.1.7 Rotate the knob for matching the colour shade similarly as step 5.1.4.

5.1.8 Take the reading in + or – in upper eyepiece and note it. (Take three concurrent readings of blank as well as sample and consider the mean value).

5.1.9 Deduce the reading of blank from the reading of sample, and calculate as follows-

[µ] 25D  =(100 x µ ) /(l  x  C)

 

Where: –

µ = Observed rotation in degree at 250c.

l = Length of polarimeter tube in decimetre.

C = Concentration of substance in % w/v.

D = The line of sodium light.

 

5.1.10 After completion of reading, take out the polarimeter tube from its cabinet & clean. Keep it in its box.  Then switch off the instrument.

5.1.11 Do analysis activity entry in instrument log book.

 

5.2  CALIBRATION PROCEDURE

5.2.1 Dry the sucrose at 105°c for 4.0 hours and prepare the 10.0%, 20% w/v, 30% w/v, 40% w/v, and 50% w/v in distilled water.

5.2.2 Fill the polarimeter tube with water / blank in which the substance is dissolved and place this in cabinet. (Temperature should be 25oc.)

5.2.3 Rotate the knob at the anterior right and match the colour shade in both sections by observing in lower eyepiece.

5.2.4 Take the reading in upper eyepiece it should be about zero. Rotate the vernier scale at the left anterior head of instrument.  Add the reading of main scale and vernier scale, and find the reading of rotation.

5.2.5 Rinse the Polarimeter tube with 10%w/v sucrose solution and fill it with 10%w/v sucrose solution and note down the rive readings and calculate the observed optical rotation by following formula: –

 

Optical Rotation  =   (Observed angle of rotation   X  10) ⁄ Sample weight in grams

 

5.2.6 Repeat above procedure for 20% w/v, 30% w/v, 40% w/v, and 50% w/v sucrose solution and record the data in format calibration of polarimeter & affixed Calibration label.

5.2.7   Calibration frequency: Quarterly.

5.2.8 Action to be taken upon failures: Contact the service engineer immediately.

 

Concentration Observed Reading Standard Range of Rotation
10 g/100ml   + 13.280 to +13.380
20 g/100ml   + 26.560 to  + 26.660
30 g/100ml   + 39.810 to  + 39.910
40 g/100ml   + 53.010   to  + 53.110
50 g/100ml   + 66.180 to  + 66.280

Find more at…

Reference links

 

https://qcequipment.wordpress.com/category/polarimeter-polarimeter-principle-polarimeter-experiment-polarimeter-theory-polarimeter-calibration/

 

http://www.gradadm.ifsc.usp.br/dados/20112/FCM0185-3/SITechPolar.pdf