What Should You Adjust First for Difficult Samples?
When pipetting feels difficult, many users first assume the problem must be their technique. And technique does matter. But in practice, with difficult samples, tip selection can matter just as much as pipetting technique.
For example, a viscous liquid may not dispense consistently.
A high-molecular-weight sample such as DNA may need gentler handling.
Delicate cells may need to be transferred with as little stress as possible.
In these situations, the issue is not always solved by changing only the way you pipette. Sometimes the answer is in the tip choice. Sometimes it is in the technique. And sometimes it is both.
That is why it is useful to stop thinking only in terms of “good” or “bad” pipetting and instead ask a more practical question:
Should the technique be adjusted first, or should the tip be changed first?
Difficult Handling Does Not Always Have a Single Cause
When a sample feels difficult to handle, the cause is not always the same.
The dispensing feel may change from one repetition to the next.
Liquid may remain inside the tip.
The sample may foam easily.
The sample may need gentler handling.
The liquid itself may simply move more slowly or resist smooth aspiration and dispensing.
All of these can feel like the same general problem: “this sample is difficult to pipette.” But the most effective solution is not always the same.
If the main issue is dispensing stability, technique may be the first thing to review.
If the problem is residual liquid or sample loss, tip choice may matter more.
If the concern is physical stress on the sample itself, the structure of the tip may become the higher priority.
That is why the first useful step is not just noticing that a sample is difficult, but identifying what exactly feels difficult about it.
If Dispensing Stability Is the Problem, Start with Technique
If the main issue is inconsistent dispensing, unstable delivery, or poor handling with foaming or viscous liquids, the first thing to review is often technique.
In those situations, reverse pipetting can be more useful than forward pipetting. Forward pipetting is the standard method and works naturally for low-viscosity samples such as water and many common buffers. Reverse pipetting, however, begins with a slight excess volume and dispenses only the intended amount, which can make handling feel more stable with certain difficult liquids.
So if the problem is that the liquid itself does not dispense comfortably or predictably with the standard method, changing technique may improve the workflow before the tip even needs to be changed.
In other words, when the challenge is mainly how the liquid is delivered, technique is often the first place to look.
If Physical Stress on the Sample Is the Problem, Start with the Tip
On the other hand, if the concern is not dispensing stability but the condition of the sample itself, tip selection may matter more than technique.
This is especially true for:
- high-molecular-weight samples,
- viscous samples,
- and delicate cells.
In these cases, pushing the sample through a narrower opening may introduce more stress than necessary. That is where a Large Bore Tip becomes relevant. Because the opening is wider, the sample can pass through the tip more gently.
Here, the main goal is not simply to improve the dispensing feel. It is to make the sample path itself less stressful. So if the priority is protecting DNA, sensitive cells, or similarly delicate materials, changing the tip may be the more natural first step.
If Residual Liquid or Recovery Is the Problem, Tip Selection Usually Matters More
Another common problem is residual liquid left behind in the tip.
If the main concern is that sample remains inside the tip, if recovery is lower than expected, or if valuable sample should be preserved as much as possible, then tip selection usually matters more than technique alone.
This is where Low Retention Tips become especially useful. Their purpose is to reduce liquid adhesion to the inner surface of the tip, which can help reduce residual liquid and improve recovery.
Technique still matters, of course. But if the liquid naturally tends to cling to the inside of the tip, handling alone may not fully solve the problem. In these situations, changing to a tip designed to reduce sample retention is often a more direct and practical improvement.
The Best Starting Point Depends on What You Want to Improve
The important point is that there is no universal rule such as “always switch to reverse pipetting first” or “always use a specialty tip first.”
The real question is:
What exactly are you trying to improve?
If the goal is more stable dispensing, start with technique.
If the goal is gentler sample handling, start with the tip.
If the goal is reducing residual liquid and improving recovery, Low Retention Tips are worth considering.
If the goal is handling high-molecular-weight samples or delicate cells more gently, Large Bore Tips are a strong option.
This way of thinking makes the decision much clearer.
Another simple way to understand the difference is this:
- Technique adjusts how the liquid is delivered
- Tip choice adjusts how the sample passes through the system and how much is left behind
That distinction is often very helpful in practice.
In Real Work, Sometimes Both Need to Be Adjusted
In actual laboratory work, the answer is not always one or the other. Difficult samples often benefit from reviewing both technique and tip choice together.
For example, with a viscous sample, reverse pipetting may help improve dispensing stability, while a Low Retention Tip may help reduce residual liquid.
For delicate cells or high-molecular-weight samples, a Large Bore Tip may help reduce physical stress, while gentler pipetting itself still matters.
So in practice, the better question is not always “technique or tip?” in a strict either-or sense. A more useful way to think is:
Which should be adjusted first, and do both eventually need attention?
That is usually the more realistic approach.
How WATSON Thinks About Difficult Samples
At WATSON, difficult samples are not approached by assuming that technique alone or tip selection alone will solve everything. What matters is understanding the sample and then deciding whether the main adjustment should happen in the pipetting method, the tip choice, or both.
Forward and reverse pipetting are different ways of adjusting technique based on how the liquid behaves during aspiration and dispensing.
Large Bore and Low Retention Tips are different ways of adjusting the tip based on sample stress, residual liquid, and recovery needs.
Because these address different kinds of problems, they should not be treated as interchangeable solutions.
That is why the first step is to define what the real issue is. Once that is clear, it becomes much easier to decide whether the right first move is changing the technique, changing the tip, or changing both.
In everyday lab work, pipetting stability is shaped not only by the pipette itself, but also by the relationship between the sample, the technique, and the tip. Understanding that relationship is what makes difficult samples easier to handle with confidence.