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Dear Readers, Welcome to the latest issue of The Magazine
Pipetting is a common and widely found laboratory technique to accurately measure and transfer small volumes of liquids. This is done using pipettes that are available in varying ranges and sizes. They consist of a plunger to pick a particular liquid amount and a calibrated tube. The parts of the pipette are sensitive to damage and most of the time, we forget their proper handling that promote this damage. In microbiology laboratories, pipettes are used to measure volumes varying between micro and millilitres. Inaccurate pipette readings can result in errors and affect the experiment. Therefore, it is imperative to maintain pipettes and handle them correctly for precise results. There are ample ways that can affect the accuracy of the results but pipetting is one of the commonest of them all.
Most of the time, not taking accountability for the equipment can affect the results. Researchers in the laboratories should consider calibrating their pipettes systematically. Their calibration is necessary for preventing errors in the results occurring due to the changed volume of the liquids. Mechanical failures such as piston contamination and damage due to pushing against the limit during the picking and expelling of the liquid affect the accuracy. Most laboratories fail to calibrate pipettes due to the high cost of services. But it is necessary for the researchers to consider monthly or quarterly calibration of the pipettes and in-house calibration every day depending on requirements.
This will improvise the results and is more effective when resources are scarce.
It generally happens when the researchers are in a haste, they immerse the tip in slant position to collect the required amount of liquid. If the tip is not immersed properly, the air can fill the space and wrong liquid volume is aspirated. The pipette should always be held straight while sucking the liquid. The tip should be left in the liquid for a second and then it should be taken out. These pauses are necessary because liquid continues to move into the tip after plunging is done. Another important factor that is forgotten most of the time is right plunging. The plunger is pressed even after its highest limit. This does not take extra liquid but the pipette can get damaged. Moreover, the tip should never be held from the pointed end and use it to take the liquid as it contaminates the reagents and samples. Thus, these factors are considered.
Pipetting : Representative image
It is generally seen that researchers use same pipette in culture room, in laminar air flow hood and on the common desk. This practice should be strictly prevented because bacterial cultures and animal cell cultures are highly sensitive to cross contamination. If same pipette is used in different areas, contamination will definitely occur, affecting the cultures and stocks. Therefore, it is mandatory to differentiate pipettes and tips for these different laboratory areas. Pipettes and tips of bacterial laminar flow hood should never be used in the culture room. This practice can prevent contamination.
If pipettes are left flat on the working area without releasing them to their highest volume, the piston lubricant will pile up on one side and the strings will be under stress. Storing the pipette vertically after releasing will prevent stress on springs and will increase their life. Moreover, their upright storage will prevent contamination and corrosion from the presence of aspirated liquid in the pipette tip. This liquid can go up in the pipette barrel causing corrosion and contamination errors during the experiment. Thus, proper training for pipette handling should be provided to researchers.
Proper cleaning of the pipettes is one of the principle requirements in laboratories and is sometimes left out of consideration. Microbiological experiments get easily contaminated with the presence of small liquids remaining in the pipettes if they are not wiped after use. Cleaning the pipettes with 70% ethanol can prevent these sources of contamination effectively. Everyday cleaning of the pipettes after use should be included in the SOP of the laboratory. Cleaning the tip and outer surface of the pipette can reduce the risk of cross-contamination and thus, the reliability of the experiments increases.
If these common factors are accommodated in daily practice, contamination can be controlled and the repeatability needs of the experiment will also alleviate. Thus, these five things should never be forgotten in microbiology laboratory.
