This document provides guidance on proper pipetting technique. It defines different types of pipets and emphasizes the importance of accuracy in laboratory analysis. Key steps for good pipetting include pre-checking pipets for defects, holding the pipet vertically when filling to the calibration line, avoiding splashing when dispensing, and thoroughly cleaning pipets after each use according to standard operating procedures. Maintaining consistent pipetting technique is crucial for obtaining reliable data.

1. Title: Good Pipetting Technique

2. Contents
1- What is pipet (Definition and Types).
2- Why good pipetting technique is required.
3- Pre-Checks before use.
4- Using of Pipets.
5- Cleaning of Pipets.
6- Past History

3. Definition: -
• Laboratory glassware is marked to indicate the volume of fluid it will contain when filled to a
specific level.
• Class A pipets are manufactured to provide high accuracy and they are required to meet the
requirements and tolerances in ASTM E969 − 02
Types of Pipet: -
1-Mohr (Graduated).
2-Volumetric (Transfer)
WHAT IS PIPET

4. WHY GOOD PIPETTING TECHNIQUE IS REQUIRED ??
• To reduce frequent and repetitive errors due to wrong pipetting techniques.
• To have adequacy/accuracy in the Analysis.
• To Improve the data quality with Good Pipetting Practice.
• Consistent dispensing.
• Consistent pipetting rhythm.
• To avoid the greatest potential hazard is when mouth pipetting is done instead of mechanical
suction. Mouth pipetting is never acceptable in the clinical laboratory.

5. PRE-CHECKS BEFORE USE
• Pipets should be clean and dry.
• Check and ensure that the Pipets to be used are free from cracks or scratches.
• The tip is not broken.
• Check and ensure that the correct pipet are being used which looks similar in size. (i.e. 4/5 ml,
3/4ml, 9/10ml etc.)

6. USING OF PIPETS
FILLING THE PIPET
• Hold the pipet vertically at eye level and insert the tip into the water.
• Pipets can be filled with a rubber bulb
• Do not insert the pipet too far into the bulb or force the bulb on the pipet.
• Place the rubber bulb at the top of the pipette and squeeze it to empty it of air.
• Then, with the tip of the pipette submerged in the solution (to be pipetted), gently relax
the bulb to draw solution up into the pipette.
• Always keep the tip of the pipet below the surface of the liquid , else air would be drawn
into the Pipet
• When the solution is about 20 mm above the calibration mark of the pipet, remove the
bulb and place the index finger on top of the pipet to prevent the water level from falling
• Remove the pipet from the solution and gently wipe the pipet with a soft tissue paper
• By releasing the pressure of the index finger, allow the water level (meniscus) to fall until
it reaches the calibration mark

7. USING OF PIPETS Cont..
DISPENSING FROM A PIPET
• Place the pipet into the receiving container and release the solution
• Avoid splashing into the receiving container
• Avoid releasing liquid with high speed
• Do not blow any remaining water out of the lower tip of the pipet.

8. USING OF PIPETS Cont..
READING A MENISCUS
• The meniscus is the curve seen at the top of a liquid in response to its container.
• The meniscus can be either concave or convex, depending on the surface tension of the liquid and
its adhesion to the wall of the container.
• Most liquids, including water, present a concave meniscus.
• Get eye level with the meniscus.
• For water and colorless liquids, this is the bottom of the meniscus.
• For colored liquids, the top of the meniscus needs to be read/ considered

9. CLEANING OF PIPETS
• Glassware must be sufficiently clean to ensure uniform wetting
• When clean, the walls will be uniformly wetted and the water will adhere to the surface in a
continuous film.
• If films of dirt or grease are present, the meniscus may crinkle at the edges and liquids will not
drain properly and will leave water drops on the internal walls.
• Lack of cleanliness can cause errors in setting a meniscus and incomplete wetting/drainage of the
calibration liquid (generally water.)
• Glassware should be cleaned immediately after use
• Clean the pipets as per SOP # SOP-QCD-GEN-014
• Soak pipettes after use in a tall jar containing 2% Extran neutral solution before washing.
• Drain and wash with potable water several times.
• Finally rinse with purified water and dry in an oven at 60°C for a drying time minimum of 180
minutes
• After drying keep the pipet in the designated place for further use.

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