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Analytical Balance Calibration

Procedure to calibrate the Analytical Weighing Balance as Drift check, Performance check and Measurement uncertainty check as per USP.


Calibration procedure:

Internal calibration

Analytical Balance Calibration in PharmaceuticalsIt shall be performed as per the manufacturer’s instructions.
Drift check
For the calculation of the drift 10 mg weight shall be used.
Note down the 10 measurements of the 10 mg weight in the performance check log. (Attachment no. 01)
Variation in the observed weight from the mean value does not exceeds  ± 0.2 mg.
The 10 mg weight shall meet the performance check criteria of the mass value i.e. 0.1% of actual mass value.
E.g. For all the 10 measurements of 10 mg weight, variation in the weighing cannot exceed 0.01mg.
Performance check
After the Auto calibration put 1 mg, 2 mg, 5 mg, 10 mg and 20 mg weights individually. The measurement shall be within the 0.1% of actual mass value of the individual weight as given in the performance check log.( Attachment no. 02)

Measurement uncertainty check

The measurement of uncertainty shall be carried out by using 10 mg weight.
Put the external weight of 10 mg on the pan and note the 10 measurements. (Attachment no. 03)
Calculate the measurement of uncertainty as follows.
Measurement uncertainty =     Standard Deviation X 3    
                                               Actual Mass Value
Measurement of uncertainty shall be Not More Than 0.001.
Calibration frequency: It shall be performed daily, after any maintenance, after the relocation and after the power failure of the balance.
Each manufacturer supplies the maximum loading condition of the balance. The calibration of the balance shall be designed in such a way that the performance check weights cover the entire loading range of the balance. Lower and higher load limits shall be checked for the performance check. Before calibration make sure that the level bubble is in the center of the indicator and if internal calibration facility is available in the balance then it shall also be performed daily before performance check of the balance.

Always use a check weight appropriate for the particular balance. E.g. a 100 – mg check weight might be selected for a balance that has a load limit of 150 mg. Thus the operator must know the maximum capacity of the balance to select the correct check weight.

Attachment-1: Performance Check Log of Microbalance
Instrument:_____________________                                  Code No :______________
Make         :_____________________                                 Model   :_______________ 

Level indicator check
1 mg

2 mg
5 mg
10 mg
20 mg
Weight box no. and valid upto
Done by
Std. Wt. Cal No. Þ

Bubble should be in Center
+ 0.1% of
 Std. Weight
(        to        )
+ 0.1% of
 Std. Weight
(        to        )
+ 0.1% of
Std. Weight
(        to        )
+ 0.1% of Std. Weight
(        to        )
+ 0.1% of Std. Weight
(        to        )

Attachment-2: Auto Performance Check Log of Microbalance
Instrument:_____________________                                                        Code No :______________
Make         :_____________________                                                       Model   :_______________ 
Check level indicator (Bubble should be in center) : _________________________________

                                                                  (Paste Performance check chart here)
Calibrated by : _______________                                               Date : ____________________
Checked  by : _______________                                                 Date : ____________________
Attachment-3: Measurement Uncertainity Check of Microbalance
Instrument:_____________________                   Code No :______________
Make         :_____________________                  Model   :_______________ 

Std. Wt.
Std. Wt. Cal. No.
Observation of Uncertainty
Less than or equal to 0.001
Weight box no. and valid upto
Done by
Checked  by

10 mg


                     Measurement uncertainty =     Standard Deviation X 3    
                                                                      Actual Mass Value

Ankur Choudhary is India's first professional pharmaceutical blogger, author and founder of Pharmaceutical Guidelines, a widely-read pharmaceutical blog since 2008. Sign-up for the free email updates for your daily dose of pharmaceutical tips.
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1 comment:

Nitin Patil said... on 2/5/16 19:57

Can we take weight for analysis in-between of monthly calibration?

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