Follow
1.0 OBJECTIVE
To provide general guidance in the technique of pipetting during analysis.
2.0 SCOPE
To pipette liquid samples accurately with pipettes that are calibrated to deliver.
3.0 RESPONSIBILITY
3.1 All the analysts are responsible to follow the procedure described in this SOP.
3.2 Overall responsibility for training, implementation & follow-up with the QC Manager or his/her nominee.
4.0 ACCOUNTABILITY
4.1 Head of Quality.
5.0 PRECAUTIONS
5.1 Before starting pipetting, make sure that the pipette is clean & dry.
5.2 Do not force the liquid out of the pipette to finish the job faster.
5.3 Do not hold the wiping gauze directly under the orifice of the pipette.
5.4 Never practice mouth pipetting, this is universally prohibited.
6.0 PROCEDURE
6.1 Make sure that the pipette is clean and dry.
6.2 Place the tip of the pipette below the surface of the liquid. Using a pipetting bulb or other suitable pipetting device, suck the liquid up in to the pipette about 1 inch above the volume mark.
6.3 Allow the pipette to drain completely to a waste container.
6.4 If any drop of liquid clings to the inner wall of the pipette, select a different one and go to step 6.1.
6.5 If the pipette drains completely, with no sign of liquid remaining on the inner surface of the pipette wall, Once again, suck up liquid to just above the mark.
6.6 Using an absorbent tissue (wiping gauze) or other suitable material, wipe the lower outside of the pipette that was in contact with the liquid during suction making sure that no liquid remains on the outer surface. Do not hold the wiping gauze directly under the orifice of the pipette.
6.7 Slowly drop the liquid level in the pipette into a waste container to the calibration mark where the meniscus is level with the calibration mark. The calibration mark should be at the eye level.
6.8 Allow the contents to drain into the sample receiving vessel.
6.9 For non-viscous liquid, allow the pipette to drain for about 15 sec after the liquid has been dispensed.
6.10 For viscous samples, allow the pipette to drain for about 45 sec after the liquid has been dispensed.
6.11 Do not blow out the pipette or rinse the inner walls down with solvent. Volumetric pipettes are calibrated to deliver by spontaneous drainage.
6.12 The following four important points to remember during the delivery:
• Hold the pipette as vertically as possible
• Do not force the liquid out of the pipette to finish the job faster.
• Do not place the tip of the pipette on the bottom of the glassware in order to prevent obstruction of the free flow. When the level of the liquid reaches the lower end of the pipette, touch the tip of the pipette to the side of the receiving container until the flow is complete.
• At the end of the delivery, do not leave the tip of the pipette in contact with the liquid. The liquid may rise back into the pipette by capillary action.
