SOP for operation & calibration of Analytical Balance

1. OBJECTIVE:

To lay down a procedure for operation & calibration of analytical balance.

• SCOPE:

This procedure is applicable for procedure for operation & calibration of analytical balance.

• RESPONSIBILITY:

QC Officer/ QC Executive

• ACCOUNTABILITY:

QC Manager.

• PROCEDURE:
  • Cleaning of the Instrument:
    • Remove powder if any, from inside the balance using soft nylon brush & wipe with clean, dry mop.
    • Remove weighing pan & wipe it with a soft nylon brush, if required, wipe with clean, cloth socked in 70% IPA solution & dry the pan completely before mounting.
    • Wipe carefully inner side of the balance with a clean moist cotton mop with IPA 70% solution in water, without disturbing the balance & finally wipe dry with a clean dry cotton mop as and when required to clean completely.
    • In case of dirty spots or stains on the body, use cotton balls soaked in 70 % IPA solution in water.

 Calibration:

Ensure Spirit level before start the calibration. Perform the Internal calibration as describe in Daily Verification.

Sensitivity:

Place the certified weight of 100 g at the centre of the pan and allow to stabilizing the displayed weight then take print and record the observation of weight in “Monthly calibration record of analytical balance”.

Calculate the Difference: Observed weight-Actual weight

Acceptance Criteria:

The difference between certified value and the observed value for 100 gm weight should not be more than ± 0.1gm (± 0.10 % of actual weight)

Eccentricity Test:

Tare the analytical balance to zero. Place the 100 g weight on the balance weighing pan with the help of forceps at position 1 and allow the balance to stabilize and press print key. Now repeat the same procedure for 2, 3, 4, 5 and 6 as shown in diagram and record the observations.Consider actual weight as per weight box calibration certificate and calculate the difference against the acceptance criteria.

Record the observations in “Monthly calibration record of analytical balance”.

Acceptance Criteria:

The difference between certified value and the observed value of 100gm should not be more ± 0.1gm.

Repeatability:

Measurement of Repeatability:

Weigh certified weight of capacity 10 gm ten times each, record the observations in “Monthly calibration record of analytical balance” Annexure- II and determine the standard deviation

Calculate the repeatability using following formula.

Calculate the repeatability using following formula.

                                                           2 X Standard deviation X100

 % Repeatability =   —————————————————————

                Minimum Weight

Note: – at the time of calculation of repeatability, if the standard deviation obtained from 10 replicates weighing is less than 0.41d, where d is scale interval (i.e. 0.00001, replace this standard deviation with 0.41d and calculate the repeatability as given below

                                                           2 X 0.41d X100

 % Repeatability =   —————————————————————

                                                        Minimum Weight

                                                               2 X Standard deviation X100

 Minimum Weight =   —————————————————————

                             0.1

Acceptance Criteria:

Repeatability  not more than 0.10 %

Linearity test:

Perform the linearity test by putting the certified weights of 20mg, 50mg, 100mg, 500mg, 1gm, 5gm, 20gm, 50 gm, 100gm and 200gm.

Tare and open the cover of glass shield and place the 20 mg test weight on the balance weighing pan with the help of forceps and allow the balance to stabilize and press print key.

Further take weight of 50mg, 100mg, 500mg, 1gm, 5gm, 20gm, 50 gm, 100gm and 200gm one by one and Record the observations in “Monthly calibration record of analytical balance”

Acceptance Criteria:

The difference between certified value and observed value for weight 20mg, 50gm, 100mg, should be ± 0.1mg and for weighs 500mg, 1.0gm, 5.0gm, 20.0gm, 50.0gm, 100gm, 200gm should be ± 0.1%.

Calculation for measurement uncertainty:

Calculate the average of ten value of certified weight obtained under repeatability.

Calculate the standard deviation of ten value of certified weight obtained under repeatability.

Calculate the random error; random error is 3 time of standard deviation.

Calculate the systematic error, systematic error is the difference of actual weight of certified weight and average value of certified weight under repeatability.

Measurement uncertainty = (random error + systematic error) x 100 / actual weight of certified weight. Record the observations in “Monthly calibration record of analytical balance”.

Acceptance Criteria:

Measurement uncertainty shall be less than 0.1%.

Frequency of Calibration: Verification of balance shall be done daily basis and calibration shall be done monthly basis.

Preventive Maintenance:

The preventive maintenance shall be done on yearly basis from the outside approved agency.

 TRAINING:

Trainer   : Manager – Quality Control

Trainees : Staff of the QC departments

DISTRIBUTION:

Master Copy                  :           QA Department

Controlled Copy            :           QC Department

Display Copy                 :           QC Department

ATTACHMENTS:

NA

REFERENCES:

In-House

ABBREVIATIONS:

Abbreviations	Extended Form
SOP	Standard Operating Procedure
NA	Not Applicable
QC	Quality Control
Sr. No.	Serial Number
QA	Quality Assurance
DEPT.	Department
IPA	Isopropyl Alcohol
%	Percentage