Operation and Calibration of Refractometer SOP (Make-Rajdhani)

SOP for Refractometer Calibration as per Indian Pharmacopoeia.

• SOP Covers below points:
  • Precautions
  • Operation of Refractometer
  • Calibration of Refractometer
  • Refractometer Calibration format

1.0 OBJECTIVE :

• To provide a procedure for Operation and Calibration of Refractometer.

2.0 SCOPE :

• This procedure is applicable to RAJDHANI make Refractometer Instrument.

3.0 RESPONSIBILITY :

• Quality control Chemist and above

4.0 ACCOUNTABILITY:

• Quality Control Head

5.0 PROCEDURE :

Refractometer is a laboratory device which measure the degree to which the light changes direction, called the angle of refraction/ Refractive index. 

The instrument is used for checking of Refractive Index of transparent liquid having Refractive Index between 1.300 to 1.700.

5.1 PRECAUTION

• Clean all parts of Refractometer including eye lens, prism and mirror before and after use with the help of tissue paper.
• Keep the instrument in its wooden box after use.
• The temperature should be carefully adjusted and maintained since the refractive index varies significantly with temperature.

5.2 OPERATION

• Open the wooden box and carefully remove the instrument from box.
• Place the instrument on table where adequate light can be reflected through mirror.
• Open the prism lock and place 2-3 drops of sample onto the lower prism using a clean pipette, making sure that you do not touch the prism with the pipette.
• Allow the liquid to smear on lower prism surface quickly, close the prism lock.
• Adjust the eye piece cross wire with the knob by rotating it in a clockwise or anticlockwise direction so that the sharp demarcation line passes through center.
• In case of any difficulties for making these adjustments or uneven interfaces or blobs of black colour is seen, that is probably because enough sample on the PRISM is not available.
• If a rainbow of colours is observed, turn the Fine Adjust knob until a sharp interface is obtained.
• If observation is close to the index of refraction of sample, the view in the eyepiece shows a dark region on the bottom and a lighter region on the top.
• Once a crisp demarcation between the light and dark regions is reached, turn the handwheel on side to place the borderline exactly on the center of the crosshairs as shown below,

• Sharp demarcation is produced in the form of circle having half light and half dark portion.
• A knob provided just above the prism can do fine adjustment.
• Note down the reading from the scale with the help of magnified lens of the instrument as below,
  • The left side of scale indicate Refractive Index Range of scale is 1.300 to 1.700.
  • The right side scale (sugar at 20° 1996) is not used here as it indicate the concentration of sugar in water.
  • View the scale and read your R.I. where the horizontal line crosses the right scale.
  • The example shown here has a refractive index of 1.342 .
  • The refractive index is unit less number.

• Open the prism and wipe the upper and lower plates with a tissue moistened with acetone. Leave open to dry.

5.3 CALIBRATION

• Observe the refractive index of the following liquids which is as per Indian Pharmacopoeia.

Reference Liquid	Temperature of liquid	Standard Refractive Index	Limits
Distilled Water	25°C	1.3325	1.332 – 1.334
Toluene (Extra Pure grade)	20°C	1.4969	1.495 – 1.497
Carbon Tetrachloride (Analytical Reagent grade)	20°C	1.4603	1.459 – 1.461

• FREQUENCY : Quarterly

 6.0 ABBREVIATIONS:

Abbreviation	Expanded form
°C	Degree Celsius
R.I.	Refractive index

7.0 ANNEXURES:

Annex. No.	Title
01	Calibration of Refractometer

8.0 SOP REFERENCES

• Manual of Refractometer
• Indian Pharmacopoeia

END OF THE SOP

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ANNEXURES :

Annex. No. 01 Calibration of Refractometer

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