November 2019 − Eppendorf News
Whether they are hand-labeled, equipped with a barcode or labeled using a datamatrix-code: laboratory samples must carry an ID.
Over many years you have collected hundreds, or even thousands of samples – samples that are the result of years of hard work, samples of high value. Sample storage at –80 °C should be safe and reliable, but also allow samples to be easily identified by the label. “Stored samples must be labeled” – in principle, every lab member confirms this. In reality, you always find some (or even more) vessels in your ULT freezer without any labeling or with labeling based on hieroglyphs. No one can read what is in the vessel, when it was created and to whom it originally belonged. In many labs, there is a second rule: non-readable vessels are discarded as soon as they are found.
How to improve?
If you prefer handwriting, a simple piece of transparent tape improves the stability and, ultimately, the readability of the writing. Based on the ergonomic aspects of easy reading, the contrast between letters and label background should be maximized.
Printed letters are easier to read compared to handwritten letters, independent of the author. Special adhesive labels based on water-resistant paper and water-resistant printing are the next step. Labels should be attached to the side of the tube; the lid surface is challenging due to the small area.
When combining both aspects, a white label with black printed letters on a vessel is recommended to make reading and sample identification as easy as possible for everyone.
Multiple barcodes in use
The best choice for safe sample identification is to use barcodes. A barcode is an optical representation of data, which is machine-readable. This means it is readable by a scanner – for example a handheld barcode-scanner such as the one we encounter in the supermarket. The label may be limited to the pure barcode or barcode plus plain writing for human readability. The barcode can be printed on adhesive labels or directly printed/ lasered on vessels.
Today, many different barcodes are in use:
• A classic “1D barcode” codes data by varying the width of the parallel lines as well as their spacing. 1D barcodes are based on different types (i.e. languages), e.g. type 128.
• Two-dimensional codes (2D) are based on specific geometric patterns. The codes can handle far more information on the same area compared to 1D barcodes. These 2D codes have different languages as well.
• QR codes are commonly known from printed internet addresses which can be scanned by mobile devices to open the related webpage. QR codes are easily recognized by their three square spots in the corners. Some people also use them to code samples in the lab.
• 2D datamatrix codes are based on a finder pattern that consists of two constant (mainly black) lines at the left and at the bottom and an empty quiet zone surrounding this finder pattern. This area should be free of any black-white contrast.
A simple lesson: proper labeling of sample vessels, combined with organized sample management software for reliable sample management, is crucial for safe results.