Using Cap Color Coding for Visual Identification of Sample Tubes

Traceability of samples is critical during sample collection, processing, and storage. Although a majority of the laboratories use 1D and 2D barcodes on sample tubes to guarantee sample traceability, inspection of cap color will further advance the tube identification process.

Benefits of Cap Color Coding

In laboratories, cap color coding is specifically helpful in differentiating between distinct types of research purposes. Color gives a visual clue that works quicker than just text alone. Users can add cap color coding next to 1D and 2D barcodes to accelerate sample storage and retrieval, to avoid human errors, and to minimize the risk of sample loss.

Day to day, large independent laboratories or biobanks gather, process, and store various types of biological samples, such as tissue, blood, urine, DNA, or feces. These samples can be from humans or animals. Moreover, other samples such as seeds or plants can also be gathered, processed, and stored.

Process of Storing Blood Samples

The process of storing blood samples starts with blood collection. Vacuum containers are the most commonly used test tubes for collecting blood samples in high volumes. These test tubes have colored caps that denote the addition of additives to pre-treat the blood or to preserve it for further processing.

These additives might consist of anticoagulants (for example, EDTA, ACD, or potassium oxalate), a gel with intermediate density between serum and blood cells, or substances that preserve specific substances or chemicals within the blood (for example, glucose).

The collected blood samples are either used for blood tests and ensuing short-term storage (in laboratories), or for long-term storage (in biobanks). In general, for long-term storage of samples, the high-volume samples of blood are subdivided into a number of aliquots. This is executed to have backups in case an aliquot degrades or is used for studies.

Due to their smaller volume, the aliquots are stored in smaller 2D-coded sample storage tubes in a 96-well rack format, such as those supplied by Micronic. Upon storage of the aliquots into these kinds of racked tubes, the 1D rack barcode and 2D tube codes are scanned (to guarantee the traceability of samples), and subsequently, the samples are stored at low temperatures. In general, the low temperatures of −20, −80, or −196 °C are most commonly used.


When the blood samples are transferred from vacuum containers into smaller sample storage tubes, it leads to loss of advantage of visual identification by cap color. To date, there is no cap color coding standard prevalent in the market for sample storage tubes that is dependent on the cap colors of sample collection tubes.

Hence, Micronic has come up with a standard cap color solution for 96-, 48-, and 24-format sample storage tubes to be in a position to identify the aliquots through cap color inspection, or to guarantee that aliquots can be easily traced back to parent samples. This solution is linked to the cap colors of vacuum containers.

A cap color is assigned to each type of blood sample (i.e. additive added to pre-treat or preserve the blood). Apart from blood samples, the cap color solution can also be applied to other samples such as tissue, feces, DNA, urine, seeds, or plants.

The following table illustrates the standard Micronic cap color coding guide for sample storage tubes.

About Micronic

Micronic is an independent organization with its headquarters located in Lelystad, the Netherlands. Micronic produces and assembles its labware in certified Class 7 clean rooms which are located in the Netherlands and the United States. Their labware equipment is also assembled inhouse. Micronic is an ISO 9001 and 14001 certified company.

Micronic products are applied worldwide in the (research) laboratories of university hospitals, forensics, agricultural, veterinary and governmental institutes, as well as companies in biotech, food, chemical and pharmaceutical industries.

Mission Statement

Our goal is to advance research by serving scientists in finding solutions that contribute to a higher quality of life. We develop and manufacture a range of Dutch-designed products to enhance the process of sample preservation and storage.

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Last updated: Aug 17, 2018 at 11:41 AM

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