When to use black carbon tips and when to use transparent tips?

The use of the type of tip (carbon or transparent) is depending on the type of pipetting technology (see “what is the difference between system liquid and air displacement”). The technology determines the technique used for liquid level detection in the system.

Black carbon tips are used when the liquid level detection is based upon conductivity. The ions in the liquid will cause a signal through the tip when the tip touches the liquid. This signal tells the system the liquid level has been found. Systems operating on system liquid will always use the black carbon tips.

Liquid level detection can also be done using transparent tips. The basic principle is different. There will be a pressure or flow sensor in the channel. When the tip touches the liquid, the pressure in the channel changes slightly.

The advantage of the use of transparent tips is often in the price. If the application does require the use of a lot of tips, or if tips cannot be washed, this advantage increases tremendously over the lifetime of the system.

What is the difference between system liquid and air displacement?

The difference between air displacement and system liquid is in the way the pipetting is performed. Basically when having system liquid, the aspiration and dispense motion is created by moving a column of fluid (often water) through the tubing with a pump. An airgap between the system liquid and the aspirated fluid makes sure that the system fluid will not be contaminated. Off course the system fluid does not travel through the tip.

Air displacement does exactly the same, but instead of moving system fluid, it moves air. The upside of air displacement is that you will need a lot less tubing in the system, it does not require any additional fluids to be filled and maintained and so on. Especially in Life Sciences the use of air displacement over system fluid gives advantages.

Some low volume dispensing techniques, such as the BioNex Nanodrop, use pressurized system liquid. The advantage of using pressurized system liquid is an increased accuracy in the dispense enabling the system to dispense volumes of 100 nl very accurate. The airgap ass mentioned above will then also play a role in the accuracy of the dispense.

How to prevent contamination?

Contamination occurs when droplets are formed at the end of a tip, when aerosols are formed during the application and so on.

The droplets are a problem that can and must be prevented. The way to do this is by aspirating a transport airgap when traveling across the deck with liquid in the tip. This is a standard point in optimization as the transport airgap varies in size depending on a few factors (type of liquid in the tip, volume in the tip, volume to be dispensed etc.).

Aerosol formation is harder to prevent, especially in very sensitive applications. However, most liquid handlers can be equipped with a HEPA filtration unit, UV lights and other additional features to keep the system as clean as possible.

In a system, contamination is formed when the sample is aspirated into the system. A liquid handler using disposable tips will only aspirate samples in that tip. This ensures no samples in the system itself. From a manual experience, many users are persuaded to use filtered tips, also on a liquid handler. However, opposed to working manually, if the system is optimized and used correctly, there is no need for filtered tips for 99% of the applications.

In systems without a disposable tip, needles or nozzles are used to aspirate and dispense. There is a higher risk of contamination using this technique, but it does make washing easier. In regards to using nozzles, the main source of contamination is found in all connection points and especially in valves if not washed correctly.

How easy is it to add a new application?

Programming a liquid handler is a specialized task. Each liquid handler has its own software. In the beginning of automation, these software packages were very basic and required a lot of scripting knowledge. Nowadays, most liquid handlers have a ‘drag-and-drop’ software interface, decreasing the complexity of programming tremendously. Adding a basic application is often a reasonable task for a champion user.

If the application requires scheduling, parallel processing, or complex calculations, it may be wise to consult your supplier before you start programming.

GC biotech tries to enable everybody to at least use the liquid handler for most daily tasks. We do this by decreasing the complexity of the daily use as much as possible in our programming approach and with additional software skills. During the installation of each system, a user training and programming training can be provided.

What is the most efficient way to arrange my deck-lay out?

Arranging the deck layout is not bound to any set rule. The application itself and the demands on the application will determine the layout for a big part.

Why should I use an automated liquid handler in my workflow?

Automation of any laboratory workflow is based upon many demands. One of the most often heard demands is to increase the speed, but this is a wrong assumption. A technician is very often faster than a liquid handler. The advantage of automation in this case is that the hands-on time of the application is decreased drastically, enabling the option to perform other tasks such as data interpretation.

Other reasons for automating any workflow, are increasing throughput, decreasing errors and increasing reproducibility. These are all valid reasons to start looking into automation.

A liquid handler has a higher accuracy, precision and especially reproducibility over a technician. It also never needs a break (except when it’s due for maintenance) and it is not hungover after the annual Christmas party. As good as this sounds, liquid handlers have many limitations that may cause a user to not choose for automation. These are all the little tricks and adaptations that a manual pipet makes, like swirling around a crystalized particle.

When automation will become a serious option, it will not just take the place of the technician. It very often has an impact on the entire workflow, especially if there is no prior experience with automation of similar processes. A lot of the preparation work is invested in looking at the workflow and the goals of the process. Together with an applications specialist the workflow, the goals and the criteria needed for successfully automating the process are retrieved. This will help us understand your needs, and help you understand what we will do for you.