Sop for Operation and Calibration of Refractometer
This Document describes (Standard Operating procedure) Sop for Operation and Calibration of Refractometer
Sop for Operation and Calibration of Refractometer
I. Purpose & Scope:
- The Purpose of this SOP is to lay down the procedure to lay down a procedure for Operation, Cleaning & Calibration of Refractometer.
- This procedure is applicable for Operation, cleaning & Calibration of Refractometer used in Quality Control Department
II. Responsibilities:
- All Quality Control personnel shall be responsible to follow and implement this SOP.
III : Introduction and Procedural Part :
GENERAL CLEANING :
- Clean the Machine with a clean dry cloth every day. Occasionally wet cloth dipped in dilute soap solution may be used.
- A precaution has to be taken to clean the instrument immediately with dry cloth to remove the moisture.
BASIC OPERATION:
- Remove the instrument from the wooden cabinet ,by unfastening the knob on the top of the instrument and remove all packing
- To ensure safety of the reflector, move it away from underneath the prism box
- To check liq. Sample, simply open the prism box by shifting the direction of the lock .Now place few drop of sample on the lower prism & simultaneously close the prism box so that a thin layer of sample is squeezed between the prisms.
- Position the reflector should underneath the prism box. Using a table lamp expose light on the reflector. Now looking in the cross-wire eyepiece, adjust the reflector for better illumination.
- After the sample is placed in the prism box or the test piece has been attached to the upper prism the refraction creates a shade in the cross-wire. The shade is brought in the center of cross- wire, by rotating the control knob in either direction
- Rotate the dispersion scale in either direction to eliminate the colour bands visible on the edge of the shade, to attain sharp borderline.
- Simply read the refractive index of the sample in the scale eyepiece.
- After testing or calibration apply a small amount of ethanol to a cotton swab & gently clean the prism. Now using dry cotton wipe the prism. Make sure not to scratch the prism.
CALIBRATION OF REFRACTOMETER:
- Ensure the cleanliness of instrument before doing calibration.
- Temperature should be carefully adjusted and maintained since the refractive index varies significantly with temperature.
- Place the instrument on a table where adequate light can be reflected through the mirror.
- Put two to three drops of sample, close properly. Use following liquids for calibration.
Reference Liquid | Standard RI | Tolerance |
Distilled water at 25º C | 1.3325 | ± 0.0001 |
Carbon Tetrachloride at 20°C | 1.4603 | ± 0.0001 |
Toluene at 20°C | 1.4969 | ± 0.0001 |
α-Methylnaphthalene at 20°C | 1.6176 | ± 0.0001 |
- Allow the liquid to smear on the lower prism surface, quickly close the prism.
- Note down the reading from the scale with the help of the magnified lens of the instrument.
- Record the observations in a format as per Annexure I – Record for calibration of Refractometer
- If any discrepancy observed during operating the instrument report to QC Manager & notify the defect to Maintenance Manager to rectify the defect. Affix ‘Under Maintenance Label’ on the instrument.
- Handle the out of calibration results as per specified SOP.
- Maintain the instrument usage log book as per SOP Handling of instrument usage log book.
- Calibration of refractometer activity should be record in instrument usage log book.
Calibration Frequency:
- Once in three months and after each maintenance job.
ANNEXURE:
Annexure I : Instrument Calibration Record
ANNEXURE-I
INSTRUMENT CALIBRATION RECORD
Name of Instrument : Refractometer | Make : |
Instrument ID No : | Model : |
Calibration Done on: | Calibration Due on: |
A) Cleanliness of the Instrument:
Observation: Clean / Not Clean
1) Any other maintenance:
Observation: Required / Not required
B) Refractive index of Reference liquid
Sr.No. | Reference Liquid | Observation | Acceptance criteria | |||||
1 | 2 | 3 | 4 | 5 | Mean | |||
1 | Water at 25°C | 1.3324 to 1.3326 | ||||||
2 | Carbon Tetrachloride at 20°C | 1.4602 to 1.4604 | ||||||
3 | Tolune at 20°C | 1.4968 to 1.4970 | ||||||
4 | α-Methylnaphthalene at 20°C | 1.6175 to1.6177 |
Remark: The instrument is calibrated and Complies / does not comply with the acceptance criteria
Calibrated By: Checked By: Approved By:
Date : Date : Date :