Serological Pipette VS Volumetric Pipette

What is a serological pipette？

Serological Pipette, also known as graduated pipette, is a linear graduated pipette that can be used for measuring a variety of volumes. The scale is evenly distributed from top to bottom, and common specifications include 1 ml serological pipette, serological pipette 2ml, 5 ml serological pipette, 10 ml serological pipette, 25 ml serological pipette, 50ml serological pipette, etc. It can be used with a pipette controller or a ball pipette.

From pipetting to storage: How do serological pipettes improve experimental efficiency? The supporting tools cannot be ignored!

A common tool used with disposable serological pipettes is the Pipette Controller, also known as a “pipette gun” or “electric pipette.” It can precisely control the speed of aspiration and discharge, improve experimental efficiency, and significantly reduce human error and hand fatigue. Benefits of serological pipette controllers include:

• Easy operation: no need to suck with mouth or pinch with hands, ergonomic.
• Sensitive suction and discharge control: especially suitable for operating large-capacity pipettes (such as 50 ml serological pipette).
• Adapt to multiple specifications of pipettes: universal design, supports the use of 1-100mL pipettes.

Many laboratories overlook a “key detail”: how to store the pipette after use? Placing it flat not only makes it easy to roll off and contaminate the scale surface, but also increases the risk of breakage. At this time, the dedicated serological pipette holder plays an irreplaceable role. The practical value of the stand includes:

• Neatly store pipettes of different specifications to avoid cross contamination.
• Prevent rolling and collision, especially suitable for glass pipettes.
• Convenient for drying and cooling after sterilization.
• Some stands can rotate 360°, which is convenient for multiple operators to share.

What is a volumetric pipette?

A volumetric pipette is a high-precision pipetting tool designed to transfer a fixed volume of liquid. It is usually made of glass and has a single scale line (such as 10 mL, 25 mL), which means that it can only measure that specific volume of liquid. Compared with graduated pipettes or micropipettes, its advantages are smaller errors and better repeatability, and it is widely used in experimental processes that require strict volume control. The main features of quantitative pipettes are as follows:

• High precision and high repeatability: more accurate than graduated pipettes, suitable for trace error sensitive experiments.
• Fixed volume transfer: each pipette is calibrated for only one volume, suitable for standardized operations.
• Mostly made of glass: easy to clean, corrosion-resistant, and reusable (disposable plastic models are also available).
• Used with rubber suction balls or pipettes: to control the suction and discharge of liquids.

Why is it still irreplaceable?

• The authoritative choice for precise quantification

Quantitative pipettes are calibrated with standardized scales, usually in accordance with ISO or ASTM standards. When used with volumetric flasks or burettes, they can achieve almost error-free solution configuration. Especially in titration analysis and drug solution configuration, they are often used as “golden quantitative tools”.

• Simple structure, clear error control

There are no complicated buttons, springs or electronic devices. All sources of error come from the controllable range of human operation. With skilled techniques, extremely high levels of accuracy can be achieved.

• Suitable for a variety of chemical environments

Quantitative pipettes made of high borosilicate glass are acid- and alkali-resistant, easy to clean, and can be sterilized at high temperatures. They are suitable for most laboratory liquid processing needs.

Although the quantitative pipette operation seems simple, in order to obtain consistent and reproducible pipetting results, you still need to pay attention to the following details:

• When aspirating liquid, it should be kept vertical and the lowest point of the meniscus should be aligned with the scale line.
• When discharging liquid, it should flow out naturally, and the residual liquid should not be blown out. The end drop is usually not included in the volume.
• It cannot be used for variable volume operation or rough estimation experiments, and is suitable for standard solution configuration or precise ratio.

How to use serological pipette?

When using a serological pipette, you need to use a pipette controller or a suction ball to achieve accurate aspiration and discharge of liquids. The steps are as follows:

First, select a pipette serological of appropriate specifications (such as 1mL, 2 ml serological pipette, 5ml serological pipette, 10mL, 25mL, 50mL, 100ml serological pipette), and check whether the packaging is intact and sterilized. After opening the package, wear gloves to avoid touching the tube body with your hands to prevent contamination.

Next, insert the plastic serological pipettes into the interface of the pipette controller (also called a pipette or Pipette Controller) to ensure that the interface is firmly sealed. Then insert it vertically into the sample liquid, slowly press the aspiration button on the controller or turn the control wheel to allow the liquid to rise to the required volume along the pipette scale line.

When aspirating, keep the pipette vertical and look at the scale level to ensure that the bottom of the liquid meniscus is aligned with the required scale line. After aspiration, move the pipette to the top of the target container and press the discharge button to allow the liquid to flow out smoothly. Some pipettes leave a small amount of residual liquid at the bottom, which is usually not included in the transfer volume (TD type). The product instructions should be followed during operation.

After use, the polystyrene serological pipettes should be properly discarded (if it is disposable) or immediately cleaned and disinfected (if it is reusable). During the entire process, avoid strong suction and discharge, tilted pipetting, repeated use of the same pipette tip, or contamination of the liquid with the pipette.

How to read a serological pipette？

First, make sure the pipette is held vertically, not tilted or tipped. When aspirating liquid, the liquid surface forms a meniscus in the tube. Due to surface tension, the center of the liquid is usually slightly lower than the sides. When reading the scale, keep your line of sight horizontally aligned with the scale line, and use the lowest point of the meniscus as the reading reference. Never look down or up at the scale line from above or below, otherwise it will cause parallax error.

It is important to note that the scale on a serologic pipette usually increases from the top (near the opening) to the tip, so for example, a 10mL pipette might have 0 mL at the top and 10 mL at the bottom near the tip. This means that you are reading the volume that has been dispensed, not the remaining volume. So if you want to aspirate 3 mL of liquid, the scale should move from 0 to 3.

When using a serological pipette with a colored scale, you should pay attention to the clarity to avoid confusion between the scale and the color of the liquid; if using a transparent liquid, you should also pay attention to avoid light reflection interfering with the reading judgment.

In short, looking straight at the lowest point of the meniscus, following the direction of the scale, and understanding the principle of “displaced volume” are the keys to accurate reading of serological pipetter. Good reading habits can effectively reduce pipetting errors and improve experimental repeatability and data reliability.

How to clean serological pipette？

First, rinse the tube with distilled or deionized water immediately after use to prevent the sample from drying out. If you are transferring cell culture media, protein-containing liquids, or corrosive solutions, you should pre-treat them with an appropriate buffer or neutralizing solution before entering the regular cleaning process.

Next, soak the pipette in a mild detergent (such as a neutral laboratory cleaning solution) for a period of time, usually 15–30 minutes, to help dissolve the residue attached to the inside. Use a special thin, soft-bristled brush to gently scrub the inner wall of the tube, taking care to avoid scratching the glass surface.

After cleaning, rinse repeatedly with a large amount of running deionized water to ensure that the detergent is completely removed. It is recommended to rinse at least three times and rinse with distilled water for the last time to remove ion residues.

If the experimental requirements are high (such as cell experiments, PCR pre-treatment), the pipette can be sterilized at high temperature and high pressure (121°C, 15psi, 20 minutes), provided that the pipette  are glass serological pipettes and has no plastic parts.

After washing and disinfecting, pipettes should be placed upside down and vertically to dry, and placed in a dedicated pipette rack or drying cabinet to avoid dust, moisture and cross contamination. If they need to be stored for a long time, it is recommended to use a dust-free cloth or a sealed container for proper storage.

Serological Pipette VS Volumetric Pipette

• If your experiment requires high-precision, fixed-volume pipetting

For example, in titration analysis, standard solution preparation, drug ratio or quantitative analysis, each liquid transfer requires extremely high accuracy. In this case, you should choose a volumetric pipette. Its structure is designed for “precisely sucking a single specific volume”, with extremely small errors and excellent repeatability. It is suitable for occasions where the experimental accuracy must be controlled at ±0.1 mL or even lower.

• If your experiment requires frequent volume changes or flexible transfer of large volumes of liquid

For example, in daily experiments such as cell culture, culture medium preparation, reagent addition, sample transfer, etc., when you need to aspirate variable volumes of liquid such as 2.5mL, 8mL or 35mL, the disposable serological pipette is a more suitable choice. It has continuous scales, rich specifications (1-50mL), easy operation, and can be used with a pipette controller to complete aspiration and discharge.

Sometimes, both types of pipettes may be used in the same experiment, for example, a quantitative pipette may be used to prepare standard solutions, and a serological pipette may be used to dispense samples or add media.