What factors affect laboratory pipetting accuracy, and how to solve it?

Regular calibration

Routine laboratories calibrate every 6 months, and high-frequency usage scenarios (such as QC in pharmaceutical companies) need to be shortened to every 3 months.

Tip matching

Use of non-original or worn tips may result in loss of sealing and volume deviation. It is recommended to choose a tip with good adaptability. Aijin universal tip can be adapted to most pipettes on the market and comes in a variety of types, including filter and non-filter, extended and non-extended, ordinary and low adsorption, etc. Suitable tips can effectively reduce experimental errors and improve data reliability.

temperature balance

Before the experiment, bring the liquid and pipette to the same ambient temperature.

altitude correction

High altitude areas require calibration to compensate for the effects of air pressure changes on air displacement pipettes.

immersion depth

The tip is immersed 1-3mm into the liquid surface. A depth difference of more than 4mm may cause a ±3% volume fluctuation.

Aspiration speed

Release the plunger slowly to avoid bubbles and pause for 1 second to ensure complete emptying.

Tip selection

Low-residue tips can significantly reduce sample waste, and filter tips can effectively block aerosols. Aijin low-absorption tips are designed with a hydrophobic coating, which can reduce liquid residue and thereby increase the recovery rate of precious samples.

surface treatment

Wide-bore tips are ideal for delicate cellular or macromolecular samples.

The Standard Tip is a versatile tip suitable for many laboratory applications with a variety of performance requirements, from high precision to the pipetting of large volumes of liquids. The universal tips in Aijin tips are commonly used for routine liquid transfer and can meet a variety of routine experimental needs. Sterile standard tips are available for demanding applications such as cell culture.

The enlarged pore size of the tip prevents shear stress from damaging fragile cells (such as macrophages) or large molecules (such as genomic DNA).

Forward pipetting method (aqueous solution)

Press the first stop point and immerse vertically 1-3mm into the liquid surface;

Slowly release the plunger to aspirate liquid, and gently touch the container wall to remove excess liquid;

Press the first stop point to dispense the liquid, wait for 1 second and then press the second stop point to empty.

Reverse pipetting method (viscous/foaming liquids)

Directly press the second stop point to aspirate to avoid air bubbles;

When dispensing, press to the first stop point and retain the residual liquid to reduce splashing.

Repeated pipetting (batch dispensing)

After aspiration, press the first stop point repeatedly to dispense, and the efficiency increases by more than 50%.

Postural norms

Sitting posture: Adjust the seat height until your forearms are parallel to the tabletop, and your elbows are bent at 90°.

Holding: Keep the pipette upright to avoid tilting it, causing liquid to backflow and contaminate the plunger.

Tool selection

Electric pipette: Reduces the frequency of manual pressing and is suitable for processing more than 5 microplates per day.

Lightweight design: Choose models weighing less than 200g to reduce shoulder burden.

clean

Wipe the outer shell with 70% ethanol every day, and remove the cone of the tip every week to remove any residue.

lubricating

Use special silicone grease to maintain the piston and sealing rings every 3 months.

Weighing method

Pipette 10 μL of pure water and weigh it, repeat 10 times, the deviation between the average value and the theoretical value (10 mg) should be <±0.5%.

cross validation

The same liquid is pipetted with two pipettes, and the difference in results must be <3%.

chemical disinfection

Wipe the surface with 70% ethanol. After strong acid/alkali contamination, rinse and dry with distilled water.

Sterilize

High-temperature sterilizable models (such as some manual pipettes) need to be processed at 121°C for 20 minutes, and electronic models use chemical fumigation.

Aspirate and completely drain a certain amount of liquid at least three times before transferring liquid. Failure to pre-rinse tips increases evaporation within the tip space, which can result in significantly lower transfer volumes. Prewetting increases the humidity within the tip, thereby reducing evaporation.

Allow liquids and equipment to equilibrate to ambient temperature before pipetting. The amount of liquid transferred by an air-displacement pipette varies with the relative humidity and vapor pressure of the liquid, both of which are temperature dependent. Working at a constant temperature minimizes changes in pipetting volumes.

Before transferring the liquid, carefully remove the drip from the outside of the tip through the side of the receiver, making sure to stay away from the tip opening to avoid sucking the liquid out of the tip. After transfer, drain any remaining liquid within the tip by touching the tip to the side of the container before releasing the plunger. Surface tension helps draw residual liquid out of the tip.

Before aspiration, immerse the tip fully below the liquid surface. Use the same depth for the same volume of suction. Insufficient immersion, especially when using large-volume tips, may result in air aspiration. Over immersion may cause liquid to stick to the outside of the tip. Tip contact with the bottom of the container may restrict suction.

It is recommended to use special pipetting tips that match the pipette. If the models do not match, it may result in volume deviation or poor repeatability. High-quality pipetting heads have three core advantages: precision air-tight design to prevent leakage, high-quality materials without defects, and strict quality control to ensure stability, which can help experiments be carried out accurately and efficiently.