SOP FOR OPERATION AND CALIBRATION OF REFRACTOMETER

1. OBJECTIVE:

1. To lay down the procedure for Operation and Calibration of Refractometer. 

2. SCOPE: 

1. This procedure is applicable for the Operation and Calibration of Refractometer.

3. RESPONSIBILITY:

1. Quality Control Officer / Executive are responsible to follow procedure as per the procedure mentioned in this SOP. 

2. QC Head is responsible for implementation and compliance of the procedure as per this SOP.

4. ABBREVIATIONS

1. SOP    :    Standard Operating Procedure

2. QC    :    Quality Control

5. PROCEDURE: 

1. Procedure For Operation

1. Ensure that the working bench and instrument is clean.

2. Adjustment / Verification

1. Set the scale at Zero Position with the help of Scale / Prism moving screw.

2. Open the prism box, place the few drops (2-3) of purified water upon the surface of lower prism and close the prism box.

3. Observing from the field of view, adjust the position of light reflecting mirror until the illumination is good.

4. Examine from the field of view, a partly dark and partly bright image will be seen.

5. Rotate the light-focusing ring so that colored band is eliminated and a clear dividing line is seen at partly dark and partly bright position.

6. At this position, dividing line of partly dark and partly bright image should touch the intersection point of cross wires. Adjust the zero adjusting screw, if required, to get this position.

3. Examination of Liquid Sample

1. Set the scale at Zero Position with the help of Scale / Prism moving screw. After verifying the zero position, place the few drops of the sample to be examined upon the surface of the lower prism and close the prism box.

2. Examine from the field of view and rotate the prism rotating screw forward/backward till the partly dark and partly bright image is seen and dividing line touches the intersection point of cross wire.

3. Note down the reading from the scale.

2. Calibration Procedure

1. The refractive index (n) of a substance with reference to air is the ratio of the sine of the angle of incidence to the sine of the angle of refraction of a beam of light passing from air into the substance.

2. Use otherwise specified in the individual monograph, the refractive index at 20°C is measured at 20±0.5°C with reference to the wavelength of the D line of sodium (λ= 589.3nm)/ the temperature should be carefully adjusted and maintained since the refractive index varies significantly with temperature.

3. Calibration Frequency – Quarterly. Put a calibration tag after calibration.

4. If the instrument is out of calibration tag the instrument with   UNDER MAINTENANCE   label. Inform to the service engineer for rectification. Calibrate the instrument after rectification.