A pipette is an indispensable tool for the experimental operation. For the top master, it is important that the experimental error is the smallest and the repeatability is good. Then pay attention to the correct pipette. The accuracy of pipettes, which are commonly used in laboratories for precise liquid measurements, can be affected by several factors. It’s crucial to be aware of these factors and take appropriate measures to ensure accurate pipetting. Here are some key factors:
Factors affecting the precision of the pipette
Calibration and Maintenance:
Pipettes should be calibrated regularly by a qualified technician to verify their accuracy. Routine maintenance, including cleaning and lubrication, is essential for optimal performance.
Environmental Conditions:
Temperature, humidity, and air pressure can impact the accuracy of pipettes. It’s important to work in a controlled environment and allow pipettes to equilibrate to room temperature before use.
Type and Quality of Pipette:
Different types of pipettes (e.g., air displacement, and positive displacement) have varying levels of accuracy. High-quality pipettes with precision-engineered components tend to provide more accurate measurements.
Temperature:
When the room temperature is low, the hand temperature is high, which causes the air to expand, and the error often occurs when inhaling the cold solution.
Airtightness:
the joint between the pipette tip and the pipette body, and the long-term wear between the cylinders inside the gun causing errors
Suction Speed:
it is easy to cause bubbles in the tip, and it will pollute the gun head.
Volatilization of Reagent:
When a reagent having high volatility is absorbed, steam enters the tip of the pipette, and the internal pressure is increased. As a result, when the liquid is pressed out, the pressure becomes large, and an error occurs.
User Technique:
Proper pipetting technique is crucial. This includes using the correct pipetting angle, maintaining a consistent and steady pipetting speed, and ensuring the tip is fully immersed in the liquid.
Tip Quality and Fit:
Pipette tips should be of high quality and compatible with the specific pipette model. A secure and tight fit between the tip and pipette is necessary to prevent leakage or inaccuracies.
Handling and Storage:
Pipettes should be handled with care to avoid damage to the piston, seals, or other components. When not in use, they should be stored in an upright position in a clean and protected environment.
Liquid Viscosity and Surface Tension:
Highly viscous or volatile liquids may behave differently during pipetting, potentially leading to inaccuracies. Understanding the properties of the liquid being pipetted is important for accurate measurements.
Aspiration and Dispensing Speed:
The rate at which the pipette bulb or plunger is depressed and released can affect accuracy. It’s important to follow manufacturer recommendations for aspiration and dispensing speeds.
Contamination and Cross-Contamination:
Contaminants on the pipette or within the tip can lead to inaccurate measurements. Regular cleaning and use of filtered tips can help prevent this issue.
Static Electricity:
Static charges can cause small amounts of liquid to cling to the tip, affecting the accuracy of the pipetting. Antistatic measures, such as using antistatic pipette tips or a neutralizing solution, can help mitigate this issue.
Sample Volume:
Pipettes tend to be most accurate in the middle range of their volume range. Extreme high or low volumes can lead to reduced accuracy.
Human Error:
Carelessness, distraction, or improper training can contribute to inaccuracies in pipetting. Proper training and attentiveness are crucial for reliable results.
By being mindful of these factors and implementing best practices for pipetting, laboratories can greatly improve the accuracy and precision of their measurements, ensuring reliable and reproducible experimental outcomes. Regular maintenance, calibration, and adherence to manufacturer guidelines are key to achieving accurate pipetting results.
In addition, Hawach does not recommend the use of ordinary pipettes for strong volatile liquid transfer. If it is necessary to remove highly volatile liquids, the pipette should be disassembled immediately after the pipetting to allow the vapor to evaporate. At the same time, it is recommended to use external devices. Piston pipette.
Please note that the aspiration rate and the discharge rate should not be too fast, and should be slowly slowed down. Quickly sucking the pipette for 1mL and above, it is easy to cause liquid overshoot. Excessive draining increases the amount of liquid remaining.
Temperature has many effects on pipetting accuracy. The factor that has the greatest effect is the temperature difference between the delivery device and the liquid. The air gap (dead air volume) between the liquid surface and the piston experiences thermal expansion effects unique to the case.
Temperature, humidity, and air pressure can impact the accuracy of pipettes. It's important to work in a controlled environment and allow pipettes to equilibrate to room temperature before use.
Temperature and pressure affect the volume of the air cushion, which affects pipetting accuracy. Also, volatile solvents can evaporate into the air cushion, which leads to an inaccurate and lower dispensed volume than that displayed on the pipette.
The calibration of pipette is carried out by gravimetric method. When determining the volume of water, the accuracy of measurements is effected by ambient temperature, atmospheric pressure and relative humidity. These factors are usually combined to give the Z factor, used in calculation of volume of water.
Mixing is essential for an accurate serial dilution. A mixing step using half the total volume of the intermediate step introduced after every transferring step ensures an accurate and consistent serial dilution.
From improper operator technique to fluid viscosity issues, to variable environmental factors and internal pipette component damage, the sources of error are many and the potential for failure is real.
Finally, calculate accuracy by using the equation A = 100 x Vavg/V0, where A is the accuracy of the pipette, Vavg is the average calculated volume and V0 is the theoretical volume you tried to dispense. If the accuracy value lies in the 99-101% range, the pipette is considered normal and calibrated.
One common source of error is using an incorrect pipette (or tips) for your liquid sample. Our article on piston pipettes provides some excellent insight on how to reduce this source of pipetting error. Another source of pipetting error that is often encountered is working with pipettes that are not ergonomic.
Physical and chemical laboratory experiments include three primary sources of error: systematic error, random error and human error. These sources of errors in lab should be studied well before any further action.
Some Random errors while using Pipettes are : Not properly aligning the meniscus with the volume mark. Forcing the solution out of the pipette causes too much solution to be delivered. Using pipette with broken tip.
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