operation and calibration of refractometer

1.0 Purpose
1.1 To describe a procedure for operation and calibration of Refractometer.

2.0 Scope
2.1 This standard operating procedure is applicable for operation and calibration

of Refractometer in Quality Control laboratory at ABC Pvt. Ltd.

3.0 Responsibility
Officer QC/ Executive QC Preparation of SOP and follow the procedure as per SOP
Assistant Manager Reviewing and Training of SOP
Manager QC Implementation of SOP
4.0 Accountability
4.1 Manager Quality Control is accountable for implementation and compliance with SOP.

5.0 Procedure
5.1 Operation
5.1.1 Ensure that the instrument is clean.
5.1.2 Insert the plug of illumination assembly box and attach the illumination tubes to the

inlet provided on the left side of the instrument and to the adjustable clamp beneath the prism box using the small pin.
5.1.3 Turn on the illumination using the switch provided on the illumination assembly box.
5.1.4 To check the liquid samples, simply open the prism box now place few drops of the samples on the bower prism.
5.1.5 Now looking in the eyepiece focus accordingly simply by rotating the eyepiece in either direction.
5.1.6 After the sample is placed in the prism box. The refraction creates a shade in the crosswire box.

The shade is to be brought in the center of the cross-wine (where they intersect) using the scales

know located on the left side of the instrument.
5.1.7 Rotating the dispersion scale located on the right side in either direction, eliminate the

colour bands visible on the edge of the shade to attain sharp borderline.
5.1.8 For examining plastic bodies such as resin detach the lower prism & soften the material by

heat and smear a little on the exposed surface of the upper prism. To examine crystals or

glasses a specimen must be prepared similar to the standard list piece.

5.2 Calibration (Frequency: after 6 Months)
5.2.1 Ensure that all the parts including eye lens and prisms are clean before operation.
5.2.2 Turn on the illumination using the switch provided on the illumination assembly box.
5.2.3 Use thermometer and water jacket with tubes to make the constant temperature of sample compartment.
5.2.4 Open the prism lock and place few drops of distilled water at the temperature 25°C.
5.2.5 Allow the distilled water to smear on the lower prism surface quickly close the prism lock.
5.2.6 Adjust the eyepiece cross wire with a knob by rotating it in a clock wise or anti-clock wise

direction so that the sharp demarcation line passes through its centre.
5.2.7 Sharp demarcation is produced in the form of a circle having half-light and half dark portion.
5.2.8 Fine adjustment can be done by a knob provided just above the prism.
5.2.9 Note down the reading from the scale with the help of the magnified lens of the instrument.
5.2.10 Clean the instrument and repeat the procedure for carbon tetra chloride and Toluene measure at 20º±0.5° C.
5.2.11 Document the activity in Calibration Record Format (Annexure I).
5.2.12 Report any discrepancy observed during calibration of instrument to Quality Control

Manager or his designee for corrective and preventive action.

5.3 Cleaning
5.3.1 Clean the instrument after listing sample applies a small amount of acetone to cotton swap

and gently clean the prism. Use dry cotton or tissue paper wipe the prism make sure not to scratch the prism.
5.3.2 After use the instrument Clean and keep under cover.
5.4 Precaution
5.4.1 Handle the instrument properly.
5.4.2 Temperature should be carefully adjusted and maintained since refractive

index varies significantly with temperature.
5.4.3 Quality Control Manager or his designee informs the defect to Maintenance Department service

engineer to rectify the defect. Affix ‘Under Maintenance’ label on the instrument.

6.0 Reference
In House Specification

7.0 Attachments
Annexure I : Refractometer Calibration Format

8.0 Distribution
Distribution of the controlled copy to concerned departments.
Additional copies may be issued for specific purpose.

9.0 ABBREVIATIONS
QA : Quality Assurance
QC : Quality Control
SOP : Standard Operating Procedure

10.0 REVISION HISTORY