Calibration of Analytical Balance SOP

SOP for Calibration of analytical balance | Daily and Monthly calibration of analytical balance |

• Analytical Balance SOP covers below points:
  • General instruction for operation of analytical balance
  • Calibration parameters for calibration of analytical balances
    • Daily calibration of Analytical balance:
    • Monthly calibration of Analytical balance:
      • Accuracy check
      • Repeatability (Measurement of Uncertainty)
      • Eccentricity check
      • Off-Center Load Test
  • Calibration format for Daily calibration of Analytical balance:
  • Calibration format for Monthly calibration of Analytical balance:

1.0 OBJECTIVE :

• To define procedure for calibration of Analytical Balances.

2.0 SCOPE :

• This procedure is applicable for following balances used in Quality Control Department.

Make	Model No.	Capacity	Least count	Operational range
Shimadzu	AUW120D	42 gm	0.01 mg	1 mg to 10 gm
Citizen	CV220	220 gm	0.1 mg	50 mg to 200 gm

3.0 RESPONSIBILITY :

• Quality Control Chemist and above

4.0 ACCOUNTABILITY:

• Quality Control Head

5.0 PROCEDURE :

5.1 OPERATION :

• General instruction for operation of analytical balances.
  • The initial step to assemble the proper equipment, such as container for weighing, receiving vessels, forceps, spatula of proper size and so forth.
  • Use containers of size such that the loading capacity of the balance is not exceeded.
  • Ensure that the containers selected to receive the weighing material are clean and dry.
  • The balance and the surrounding work area have to be kept neat and tidy.
  • Balance door should be closed to stabilize the scale.
  • Ensure that balance should be kept on vibration free platform.
  • Ensure that air currents are not present on the location where the balance is installed.

5.2 CLEANING

• Clean the balance platform and display board with dry lint free clean cloth.
• Wipe the balance with wet lint free clean cloth.
• Wipe the balance platform with dry free clean cloth.
• In case of sensitive balance, clean the balance and the pan as per the procedure given below,
  • Remove the dust from pan with smooth nylon brush.
  • Remove the pan from the balance and clean it with wet lint free cloth.
  • Fix the weighing pan properly on the balance.

5.3 CALIBRATION

• General instruction for calibration of analytical balances.
  • If necessary, turn on the power, and allow the balance to equilibrate for at least 1 hour before proceeding with the calibration.
  • Check the spirit level of the balance; adjust the level with help of mounting screws, if required.
  • Before starting the calibration, standard weight should be kept on balance platform at room temperature for at least 15 minutes to reach thermal equilibrium.
  • Required standard weight shall be kept one by one at the center of the weighing pan.
  • Balance shall be verified daily for minimum, middle and maximum operational range of balance.
  • Do not use any solvents or compressed air for cleaning of the weighing balance.
  • Ensure the cleanliness of the instrument area.
  • Ensure the balance is clean and free from dust.
  • Balance shall be calibrated for the entire operational range of balances.
  • Ensure all the standard weights should be clean.
  • Ensure the balances are calibrated and verified before use. (All the standard weights should be calibrated once in year ± 30 days)
  • Ensure the stamping by the “Weight and Measure controlling authority” once in year ± 30 days.
  • In case of power failure, once the power is resumed, re-verify the balance and then start the further activity as per procedure.
  • If it is required to use the balance for weight which is out of operational range, the balance shall be verified for the same weight before using for that particular weight.
  • The weight displayed should be within limit of tolerance.
  • Use the balance only after rectification/ recalibration.
  • If weight displayed is not within tolerance limit then stop weighing on the balance and label as “Out of Order” and inform to Engineering and QA departments.

• Daily calibration of Analytical balances:

• Analytical balances shall be verified daily by using standard weights mentioned as follows;

Make	Model	Standard weights used
Shimadzu	AUW120D	1 mg, 500 mg, 5 gm & 10 gm
Citizen	CV220	50 mg, 1 gm, 100 gm & 200 gm

• Acceptance criteria: Observed weights should be within ± 0.10% of actual weight or graduation value (least count) of analytical balance.
• Place the weight on center of weighing pan.
• Note down the actual weight observed in daily balance calibration.
• Write remark after calibration.
• Make the entry in balance log book.
• Frequency: Daily once (Once in 24 hrs),  As and when required.

• Monthly calibration of Analytical balances:

• Accuracy check
• Calibrate the balance by using the following all different weights from standard calibrated weight box and note  down the observed weight in calibration protocol.

Make	Model	Standard weights used
Shimadzu	AUW120D	1 mg, 5 mg, 20 mg, 50 mg, 100 mg, 200 mg, 500 mg, 1 gm, 5 gm & 10 gm
Citizen	CV220	50 mg, 200 mg, 500 mg, 1 gm, 5 gm, 10 gm, 20 gm, 50 gm, 100 gm & 200 gm.

• Acceptance criteria: Observed weights should be within ± 0.10% of actual weight or graduation value (least count) of analytical balance.

• Repeatability (Measurement of Uncertainty)
• Place the standard weight on the center of the pan and record the observed weight in calibration protocol.
• Repeat the same procedure for another 9 times.
• Determine the standard deviation (σ) of ten replicate weighing.
• Calculate the Repeatability (Measurement of uncertainty) by the formula;
• Repeatability  (Measurement of Uncertainty) = 2 x σ  / Standard weight
• Where σ is standard deviation.
• Repeat above steps for other defined standard weights.
• Standard weights for Repeatability for analytical balances are as follows;

Make	Model	Standard weights used
Shimadzu	AUW120D	1 mg, 500 mg, 5 gm & 10 gm
Citizen	CV220	50 mg, 1 gm, 100 gm & 200 gm

• Acceptance criteria: The Repeatability (Measurement of Uncertainty) should be less than or equal to 0.10%.

• Eccentricity check
• Place the standard weight on the center of the pan and record the observed weight in calibration protocol.
• Repeat the same by keeping the weight on four different corner positions. (i.e., front, rear, left and right) and check the deviation from the center.
• Repeat above steps for other defined standard weights.
• Standard weights for Eccentricity check for analytical balances are as follows;

Make	Model	Standard weights used
Shimadzu	AUW120D	1 mg, 500 mg, 5 gm & 10 gm
Citizen	CV220	50 mg, 1 gm, 100 gm & 200 gm

• Acceptance criteria: Observed weight of corners should not exceed ± 0.10% from center position.

• Off-Center Load Test
• Place the standard weight on the center of the pan (Location A) and record the observed weight in calibration protocol. (Figure-1)
• Without lifting move the standard weight between the center (Location A) and rear edge of the platform (Location B) & record the reading.
• Without lifting move the standard weight halfway between the center (Location A) and front edge of the platform (Location C) & record the reading.
• Without lifting move the standard weight halfway between the center (Location A) and left edge of the platform (Location D) & record the reading.
• Without lifting move the  standard weight halfway between the center (Location A) and right edge of the platform (Location E) & record the reading.

• Standard weights for Off-Center Load Test for analytical balances are as follows;

Make	Model	Standard weights used
Shimadzu	AUW120D	1 gm
Citizen	CV220	50 gm

• Acceptance criteria: Observed weight of corners should not exceed ± 0.05% from center location.
• Take entry of monthly calibration in respective balance log book.

 6.0 ABBREVIATIONS:

Abbreviation	Expanded form
gm	Gram
mg	Milligram
%	Percentage
hrs	Hours
QA	Quality Assurance

7.0 ANNEXURES:

Annex. No.	Title
01	Daily Calibration Record – Analytical Balance
02	Monthly Calibration Record – Analytical balance

8.0 SOP REFERENCES

•  USP 42 NF 37, Chapter No. <41> and <1251>

END OF THE SOP

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ANNEXURES :

Annex. No. 01 Daily Calibration Record – Analytical Balance

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Annex. No. 02 Monthly Calibration Record – Analytical balance

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