SOP for Calibration of Polarimeter

1.0 OBJECTIVE

To describe the procedure for Operation and Calibration of Polarimeter.

2.0 SCOPE

This SOP is applicable for Operation and Calibration of Polarimeter.

3.0 RESPONSIBILITY

Officer/ Executive - Quality Control.

4.0 ACCOUNTABILITY

Manager - Quality Control.

5.0 PROCEDURE

5.1 Operation

5.1.1 Switch ‘ON’ the mains.
5.1.2 Wait till the sodium lamp glass with the full intensity of yellow light.
5.1.3 Adjust vernier scale to zero dial scale to zero.
5.1.4 View through the piece, if there is the difference in intensity of light adjust it without disturbing the dial reading by adjusting, the knurled screw of the polarizing prism.
5.1.5 It is different to adjust with the knurled screw, adjust the dividing line by rating dial and vernier scale. Note down the reading, which is Dextro or Levo and will be taken as zero error for the calculation of the optical rotation.
5.1.6 Rinse the polarimeter tube with the blank solution.
5.1.7 Fill the tube with the blank solution at the specified temperature.
5.1.8 Clean the sides of the tube with tissue paper.
5.1.9 If any air bubble comes then it must be trapped in the center of polarimeter tube.
5.1.10 Keep the polarimeter tube in its place in the polarimeter.
5.1.11 Adjust the zero on the upper scale with the help of control wheel.
5.1.12 Focus circular disc of the light with the help of field telescope.
5.1.13 By means of the control wheel, move the scale from its first position.
5.1.14 Observe the field, which is divided into two valves, light and dark.
5.1.15 Adjust the control wheel to get the equal intensity of the two halves.
5.1.16 If the index line between two scales division, therefore rotate the knurled wheel to bring the index line coincident with a scale line.
5.1.17 Note the reading in the degree of rotation.
5.1.18 Repeat the operation five times.
5.1.19 Consider the average reading.
5.1.20 Mark it as + (plus) reading if it is left to the zero and – (minus) reading if it is right to the zero.
5.1.21 Remove the polarimeter tube from the polarimeter.
5.1.22 Discard the solution from the polarimeter tube.
5.1.23 Rinse the polarimeter tube twice with the test solution.
5.1.24 Fill the test solution in the polarimeter tube at the temperature specified in the monograph/ specification.
5.1.25 Clean the tube and the sides of the glass with tissue paper
5.1.26 If any air bubbles come then it must be trapped in the center of polarimeter tube.
5.1.27 Keep the tube in its place in the polarimeter.
5.1.28 Adjust the control wheel to obtain same field condition as with the blank and note down the reading.
5.1.29 Repeat the operation at least five times.
5.1.30 Take the average of the reading.
5.1.31 Discard the test solution from the polarimeter tube.
5.1.32 Switch ‘Off’ the mains.
5.1.33 Clean the polarimeter tube with distilled water if solutions are prepared in polar solution or clean the polarimeter tube with methanol or ether if the solvent is non-polar.
5.1.34 Keep the tube in the tube box.
5.1.35 Enter the details in the logbook.
Related: Optical Activity in Pharmaceutical Analysis

5.2 Calibration

5.2.1 Switch ‘On’ the mains.
5.2.2 Wait till sodium lamp glows with the full intensity of yellow light.
5.2.3 Rinse the Polarimeter tube with distilled water.
5.2.4 Adjust the vernier scale and main dial scale to zero.
5.2.5 If two halves intensity is not metering then adjust it by turning the knurled screw of the prism box slightly. If not possible then adjust the field by rotating milled knob and vernier scale note the reading (+) or (-) side as a zero and to be considered while calibrating.
5.2.6 Fill the distilled water in Polarimeter tube.
5.2.7 Clean the sides of the tube with tissue paper.
5.2.8 Entrap any air bubble in space at the center of the tube.
5.2.9 Keep the Polarimeter tube in the place provided in the Polarimeter.
5.2.10 Adjust the zero with the help of control wheel.
5.2.11 Focus circular disc of light with the help of field telescope.
5.2.12 Observe the fields, which is divided into two halves, light and dark.
5.2.13 Adjust the control wheel to get the equal intensity of the two halves.
5.2.14 Measure optical rotation of the blank solution.
5.2.15 Note the +ve or –ve reading in the degree of rotation.
5.2.16 Repeat the step no. 5.2.5 to 5.2.15 for five times.
5.2.17 Take an average of the 5 readings.
5.2.18 Remove the Polarimeter tube from Polarimeter & discard the distilled water from the tube.
5.2.19 Prepare 10%, 20%, 30% 40% & 50% solution in distilled water of standard refined sucrose previously dried at 105ºC for 3 hours.
5.2.20 Rinse the tube with 10% solution and fill the solution in Polarimeter tube.
5.2.21 Clean the sides of the tube with tissue paper.
5.2.22 Entrap any air bubble in the space at the center of the tube.
5.2.23 Keep the Polarimeter tube in the space provided in the Polarimeter and measure the optical rotation of sample solution.
5.2.24 Note the reading in the degree of rotation.
5.2.25 Repeat the operation five times and record the readings.
5.2.26 Remove the tube from Polarimeter & discard the solution from the tube.
5.2.27 Repeat the operation with 20%, 30%, 40% and 50% solution after rinsing with the same solutions.
5.2.28 Note the readings of each concentration.
5.2.29 Remove the tube from Polarimeter and discard the solution from the tube.
5.2.30 Wash the tube with distilled water and rinse with acetone and keep in Polarimeter tube box.
5.2.31 Switch ‘Off’ the mains.
5.2.32 Enter the calculated readings in calibration record.
5.2.33 Affix calibration label.
5.2.34 Acceptance Criteria (if any):-
Difference between Std. Value and calculated value must not be more than 0.05º for 10% and 20% and not more than 0.1º for 30%, 40% and 50% solution.
5.2.35 If the value doesn't meet the acceptance criteria, inform the QA/QC Manager for further action.
Frequency of Calibration: - Monthly or after any maintenance.

5.3 Precautions

5.3.1 Polarimeter tube should be filled in such a way so as to avoid air bubbles.
5.3.2 Before taking the reading clean the Polarimeter tube with tissue paper.
5.3.3 Set the field telescope for better observation.
5.3.4 The optical elements must be cleaned and at exact alignment.
5.3.5 Tighten the end plate with caps and seal so as to make it leak proof.

6.0 ABBREVIATIONS

6.1 SOP - Standard Operating Procedure
6.2 +ve - Dextro Rotatory
6.3 – ve - Levo Rotatory

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