When it comes to pipetting technique, minor variations can have major consequences.
These differences may seem normal and insignificant; perhaps some pipetting technique variation is even expected. After all, when technicians enter the lab field they bring all sorts of training methods, education, preferences and experience with them, right? Differences in technique can be attributed to a variety of factors, but it’s important to recognize what’s at stake. Incorrect, incomplete or carelessly performed pipetting steps can – and do – directly impact test results, and might even affect patient outcomes.
What are some potential sources of over- or under-delivery when using manual pipettes? Well, just like other forms of laboratory instrumentation, even a properly calibrated pipette performs only as well as its operator.
The American Laboratory article “Best Practices for the Use of Micropipets” discusses a number of considerations. Each of them can affect pipetting accuracy and precision. And, fortunately, all of them can be managed.
These factors can alter pipetted volumes by causing the air cushion above the sample liquids to expand or contract. Errors are easily minimized by paying attention to environmental influences, and taking the necessary steps to monitor and control them.
Forward, or standard, pipetting mode is generally the best method to use with aqueous solutions. Reverse-mode pipetting can be useful for viscous or volatile liquids, but it generally over-delivers when using solutions similar to water.
How is hydrodynamic flow affected by an operator’s technique? Well, liquid sitting close to the walls of a container may behave differently from liquid at the center of the sample. A few key steps will help technicians manage this potential source of error.
Like most skills combining science with art, manual pipetting really does benefit from regular practice and attention to the finer points.
Even the best operator technique can be undermined by subpar hardware. To avoid compromising important test results, make sure you’re using the right tools for the job.
Any of these factors could potentially introduce error into test results, and multiple variations only compound the risk. That’s why it makes sense to devote time and effort to develop standardized pipetting technique through training and coaching.