The document discusses calibration procedures for an analytical balance, including drift check, performance check, and measurement uncertainty check. Key steps include using weights of 1mg, 2mg, 5mg, 10mg, and 20mg to ensure measurements are within 0.1% of the actual mass value, calculating measurement uncertainty as the standard deviation times 3 divided by the actual mass value, and ensuring calibration is performed daily and after maintenance or relocation. Environmental factors like temperature, humidity, and static electricity are also discussed as important to control drift.

1. Analytical Balance Calibration
Learn how to calibrate the Analytical Balance as Drift check, Performance check and
Measurement uncertainty check.
CALIBRATION OF TOP PAN BALANCE
Calibration procedure:
Internal calibration
It 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 weighings cannot exceed
0.01mg.
Performnce 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

2. 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 :_______________
Date
Level indicator
check
1 mg 2 mg 5 mg 10 mg 20 mg
Weight no. and upto
Std. Wt. Cal No. Þ
Limit
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 : ____________________

3. Attachment-3: Measurement Uncertainity Check of Microbalance
Instrument:_____________________ Code No :______________
Make :_____________________ Model :_______________
Date Std.
Wt.
Std.
Wt.
Cal.
No.
Observation Observation of
Uncertainty Less
than or equal to
0.001
Weight
box no.
and
valid
upto
Done
by
Checked by Remark
10
mg
Calculation
Measurement uncertainty = Standard Deviation X 3
Actual Mass Value
Drift and Its Importance in Analytical Balances
Know the causes, importance and factors effecting the drift in analytical balances.
In the pharmaceutical industry and bioscience research field, many laboratories make
use of analytical balances. The analytical balances used in the bioscience research and
pharmaceutical industry are very sensitive. These balances can be heavily affected by the
way the measuring personnel handle them and by the environment in which they are
installed. The environment in the pharmaceutical laboratory needs to be assessed by
running assessment tests. Based on the results of these assessments should be
proposed concrete measures for improving the lab environment.
The weighing instruments in a pharmaceutical lab should always operate is quick and
accurate. It should be avoided any events in the lab that would affect the analytical
balance measurements results, such as opening and closing a breeze break door, for
example. This is not an optimal way of conducting analytical balance weight
measurements. When the breeze break door is open, the weighing area’s temperature
will change because the air within the breeze break changes.
Analytical balances used in a pharmaceutical lab are used for extremely precise
measurements, such as the microbalance capable of measuring 1 millionth of a gram,
for instance. These highly accurate weighing instruments are used for quality control of
the processes involved in the pharmaceutical industry manufacturing production.

4. Related: Calculation for Determination of Weighing Range of Balances
Sometimes a phenomenon called “drift” is experienced in the weighing instruments,
including high precision analytical balances. This undesired phenomenon consists in
measurements changing in one direction or displays becoming unstable with the
passage of time. Unstable readings may occur with no weight applied or the weight
readings do not stabilize due to the drift effect. This can be explained by the static
electricity accumulated due to the dry environment and friction from insulated material.
The pharmaceutical production lines are having clean environments, controlled with 24
hour air conditioning. In such an area the humidity levels is often below 20 percent. By
moving around objects in such a dry environment the friction causes building up of
static electricity. Research has proved that people working in such a research lab or
pharmaceutical production line can build up themselves around 10,000 volts of
electricity. The effects of the static electricity become even greater under these
circumstances and they can lead to errors of dozen milligrams.
In order to avoid the static electricity build up and the apparition of the drift effect on
the analytical balances, it would be necessary that the humidity level in the weighing
instrument's installation environment to be increased over 40 percent. In case that the
static electrical build up occurs faster than the electrical discharge, it is necessary to
conduct weighing operations only after removing electrical charges from the weighing
sample and to introduce a static eliminator. It should be avoided the use of plastic
containers for the weighed items and the operators of the analytical balances should
always stay on an anti-static floor covering.
Another environmental factor that can dramatically affect analytical balances stability is
temperature. Temperature control is therefore imperative in avoiding the drift
phenomenon. This includes both the maintaining the constant temperature of the
weighing instrument as well as controlling the room temperature. For the best
temperature stability, the room should be constantly maintained whiting two
temperature degrees variation, day and night. The weighing instrument should be
always plugged in and turned on, in order to maintain its temperature constant as well.
Generally balances have an error of 2 ppm/°C.
Calculation for Determination of Weighing Range of Balances
know how to determine the operating range of the balances used for pharmaceuticals including
the analytical balances.

5. Balances are used to weigh different things as raw material, dispensed material and
samples. Sometimes very low quantity is weighed for analysis. An error in the weighed
material can cause a big variation in analytical results.
Following circumstances may cause the error in the weighing:
 Balance for analytical use must be closed; an open balance may cause
inaccurate weighing.
 Hygroscopic material gains weight when it comes in contact of the air
causing unstable weighing.
 Air flow or current in the balance room may cause disturbance in accurate
weighing.
 Unleveled surface or balance may lead to inaccurate weighing.
 Vibrating surface can also cause inaccurate weighing.
Assay, related substances and other quantitative analytical tests require accurate
weighing for better results. Near the lower and upper capacity of the balance, weighing
may be inaccurate. Therefore, a weighing range must be defined for all balances.
Related: Calibration of Analytical Balance
Weighing Range for Balances:
Some manufacturers direct in their operating manual to weigh minimum 1.0 mg on
balance having 0.01 mg least count i.e. least count X 100. But the thumb rule followed in
pharmaceutical industries for lower limit is least count X 50 and upper limit is 80% of
capacity of the balance. If any balance has operating range from 0.01 mg to 110 gm
then it should be used for weighing the material from 0.01X50 = 0.50 mg to 110X80% =
88.00 gm. Detailed guidance on the balances can be learned through OIMLR76-1 Non-automatic
Weighing Instruments.
But according to USP <41> Weights and Balances, a simple theoretical calculation can
be used to calculate the minimum weight for any balance. To weigh 10 mg sample you
have to use 10X0.1% = 0.01 mg least count balance. It shows that if you have a balance
with least count 0.01 mg, you can weigh minimum 10 mg sample on it. Other weights
can be calculated accordingly.