Each laboratory technique, from PCR and Western blot to fluorescence-assisted cell sorting and histochemical staining, has its own pitfalls. However, many common errors are ubiquitous enough to be found throughout nearly every method, particularly during basic sample preparation. Below, we’ll review several common traps and how best to avoid falling into them.
Not labeling containers beforehand
Labeling as you go is an inefficient way to identify containers during sample preparation. Handwriting in particular can be laborious, putting unnecessary strain on your hands and wrists, especially when you need to label large sets of tubes and plates immediately after a series of solutions are pipetted. It is thus essential to have each and every container accurately identified prior to initiating any assay.
Solution: Integrate printed barcode and/or RFID labels into your workflow
Pre-printing barcode and/or RFID labels with or without alphanumeric text and affixing them to all necessary containers beforehand is a quick and accurate way of tracking samples. Integrating pre-printed labels into workflows both mitigates the possibility of human error and provides a more efficient sample tracking and identification method.
Not using an appropriately sized container
It’s sometimes tempting to think that because a specific type of vial or tube is either cheaper or more immediately available, it will be suitable for the task at hand. This thinking can lead to staff using tubes that are too small or too large for given sample volumes, making it difficult to either pipette the full sample or causing unwanted spillage.
Solution: Rely on volume indicators and correct for additional volume
Most tubes are graduated, and it pays to use their markings as strict guides for how much a tube can hold. Spillage can easily be avoided by ensuring volumes no greater than those marked on the tube are used. When using small amounts in a large tube, always take note of the solution’s chemical composition, as even small volumes of water-based solutions will be difficult to fully pipette in excessively large tubes, and pipetting glycerol-based solutions can make it even harder. Try to ensure that the volume fills at least one-third of the tube, wherever possible, such that the pipette tip can fully aspirate the fluid.
Not tracking samples digitally
Tracking samples and data by hand is one of the most time-consuming aspects of laboratory work. Writing each individual sample identity into paper notebooks can take valuable time away from performing assays.
Solution: Outfit your lab with a LIMS and/or ELN
Barcode/RFID labels are already noted above, and it’s always best practice to integrate their data into a cloud-based laboratory information management system (LIMS) and/or electronic notebook (ELN). Using these systems allows you to streamline and monitor workflows, provide additional security for all lab data, plan ahead regarding the use of reagents and equipment, track all samples and inventory, and upload and analyze results.
Measuring exact amounts of a solution
This issue arises when preparing extracts and other samples for use in multiple wells of a Western blot or PCR series. When calculating volumes of samples and reagents required prior to distribution, it’s often desirable to use as little volume as needed; however, when distributing from a single tube into multiple wells, measuring for the exact amount usually means not enough sample is available for the final well, resulting in skewed sample distribution and potentially erroneous results.
Solution: Account for a slightly higher volume of initial stock
The solution to this problem is inherently simple. Calculate a slightly greater final volume to account for any potentially missing solution for the final well. If there are restrictions on the sample volume available, often running slightly less sample can be helpful to ensure experimental uniformity for the single test.
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