Weighing of Sample on an Analytical Balance

1.0 Purpose:

To lay down a procedure for Weighing of Sample on an Analytical Balance.

2.0 Scope:

The scope of this procedure is applicable for Weighing of Sample on an Analytical Balance.

3.0 Responsibility:

QC Personnel: To weigh the Sample on an Analytical Balance.

Head QC/ Designee: To Monitor the Activity.

4.0 Definitions:

5.0 Procedure:

5.1 Ensure that the instrument is clean before and after every operation.

5.2 Before loading the weight, ensure that the doors are closed properly.

5.3 Before loading the weight, ensure that the spirit level is proper.

5.4 Ensure that the Analytical Balance is calibrated.

5.5 Extreme care is essential when weighing corrosive materials like Sodium Chloride. This type of material should not be spilled on the balance pan or inside the balance housing.

5.6 Care should be taken while weighing hygroscopic material. Hygroscopic material should be subjected to minimum exposure to atmosphere as it readily absorbs moisture from the atmosphere and steadily gains weight.

5.7 Samples/Receivers that are warm or cool should be equilibrated in the laboratory before weighing is done, or else it may give erroneous/false readings.

5.8 To remove or clean any leftover sample from weighing chamber, use a small camel hair brush.

5.9 Avoid liquid spillage within the Balance compartment, as it can cause serious damage to the Analytical Balance and is difficult to remove.

5.10 Operating Procedure:

5.10.1 Weighing Procedure For Solids/Liquids (Non-volatile/Non-Hygroscopic):

• Take the receiver for weighing of sample, like Weighing paper, weighing dish, enclosed vessel (bottles, vials and flask), whichever is applicable.

• Place it on the Weighing Pan of the Analytical Balance. Wait until the Analytical Balance stabilizes and tare the Analytical Balance. Take a print.

• Add desired quantity of sample to the receiver. Close the door of the Analytical Balance. Allow the Analytical Balance to stabilize. Record the Weight (W1).

• Transfer the weighed sample into an adequate vessel/container. Weigh the Weighing receiver again (W2).

• The difference between W1 and W2 should be recorded as the actual weight of the sample weighed and transferred.

• In case sample transferred to the receiver more than required, additional quantity should be disposed as per “SOP for Disposal of Leftover Samples and Scrap”.

• Do not put back any dispensed sample back into the original pack.

• Clean the Analytical Balance using a small hair brush after the activity is complete.

• Do not leave any sample near the Analytical Balance after weighing.

5.10.2 Weighing Procedure For Viscous Liquids:

• Tare the Balance.

• Place the sample on the balance in a suitable vessel or container. Wait until balance stabilizes. Record the weight (W1).

• Transfer desired amount of sample to an appropriate vessel or container such as volumetric flask or beaker.

• Again place initial vessel or container on balance. Wait until balance stabilizes. Record weight (W2). • The difference in two weighing W1-W2 is amount of sample transferred.

5.10.3 Weighing Procedure For Hygroscopic Samples/Volatile samples:

• Place Air tight vessel (Volumetric Flask with Closure) on balance pan.

• Tare Balance.

• Add desired amount of sample in vessel and close vessel/replace closure.

• Wait until balance stabilizes and note balance reading or take printout.

6.0 Annexures:

Nil