How Safe Are Your Samples?
Plastic storage tubes are used in laboratories worldwide to store biological and chemical samples. As most plastics are supplied as sterile, pyrogen- and DNAse/RNAse-free, it is generally accepted that this guarantees product integrity. Many confuse “Clean” with “Sterile”, post production sterilisation only guarantees that there are no viable organism and does not relate to the cleanliness of the product. Few researchers ever consider that despite these apparent guarantees, plasticware can still provide a potential source of error.
Evidence shows that bioactive compounds can diffuse into solutions that come into contact with the surface of the plastic. These compounds, typically referred to as “leachables” or “extractables”, are used during the manufacturing process to improve product stability and durability. However, these compounds can have a significant impact on scientific experiments and pose a likely source of error in many assay systems. Examples of leachable interference include inhibition of enzyme activity in bioassays and falsification of nucleic acid quantification.
The aim of this evaluation was to determine if “extractables” could be detected in solvent solutions stored in FluidX external thread tubes and to compare their performance against competitor tubes.
All testing was performed by an independent 3rd party, Ig-M Co., Ltd headquarters Lab, Hyogo Prefectural Institute of Technology, Japan.
- “Extractables” – Compounds that can be extracted from the container closure system when in the presence of a solvent.
- “Leachables” – Compounds that leach into the sample from the container closure as a result of direct contact with the sample.
The following storage tubes were used in the evaluation:
- 7ml external thread transparent tube – FluidX (n=3)
- 7ml internal thread transparent tube – Competitor 1 (n=3)
- 7ml internal thread transparent tube – Competitor 2 (n=3)
- 7ml(a) & 1.3ml(b) internal thread transparent tube – Competitor 3 (n=2 + n=2)
- Tubes were filled with 80% ethanol and the caps screwed on.
- Tubes were then placed in centrifuge tubes.
- Using a shaker table, the tubes were shaken at 20oC at 120rpm for 24 hours.
- 1μl was eluted from each tube.
- Elutions were subjected to Gas Chromatography / Mass Spectrometry analysis
(Thermo Fisher Co., Ltd. GC:TRACF1300 / MS:ISQ)
FluidX Results Table:
The evaluation showed that ethanol was an effective solvent for detecting leachables in the sample storage tubes.
From all the eluted material samples, at least 2 elutions of the same tube type have common properties. It is, therefore, possible to ensure the authenticity of the data.
From MS analysis of the elution, the most likely substance was presented for each manufacturer. More certainty can be determined by using the appropriate reagent as a standard substance for comparison and comparing the measurement.
There are many different grades and types of Polypropylene resin which can be selected for various reasons including material properties of the finished product, ease of manufacturing and cost.
FluidX only uses specific Medical Grade “virgin” polypropylene resins selected for their material properties and kept consistent through the life of the product, “virgin” refers to the state the resin arrives from the manufacturer of the resin, it is relatively common practice to regrind excess or QC failed parts and add a percentage back into the process to save on costs, however this changes the properties of the end product and may require the use of additives.
Additives are Ingredients Incorporated into the Polypropylene Polymer to Stabilize or enhance its Performance
- Stabilizers – Maintain the Polymer’s Original Properties
- Modifiers – Change or Improve Polymers Performance
- Performance Additives (Slips, Anti-Stats)
FluidX does not use additives.
The evaluation demonstrated that there were obvious differences in performance of sample storage tubes between manufacturers.
Since leachable compounds from plastic resin can have an adverse and erroneous effect on scientific investigations, it is vital that the performance characteristics of the storage tube are carefully considered.
FluidX external thread tubes were the only tubes that consistently produced no detectable leachables and, therefore, offer a superior solution for long-term storage of biological and chemical samples.
Robin Grimwood, Senior Director, Stores Business Unit, Brooks Life Science Systems