The Tip of the Iceberg: How Pipette Tips Influence Results. Part 3: Not Every Tip Tolerates Every Treatment

The pipetting accuracy of pipette tips by certain manufacturers may suffer after autoclaving. This was not the case for Eppendorf tips. We describe the measures which Eppendorf takes in order to avoid the negative influences of autoclaving. Furthermore, we describe how the interference of biological assays by leachables from pipette tips is prevented. A MEA (Mouse Embryo Assay) test proves that sensitive biological systems are not influenced by Eppendorf pipette tips. Introduction We have shown in part 1 and 2 of this series (see BioNews No. 44 and 45) that pipette tips influence the performance of the system “pipette and tip” and thus the pipetting result. This was predominantly caused by the tip’s shape and its production quality. Autoclaving is a widely applied method for decontamination of pipette tips but it imposes thermal stress. For this reason, calibration was used to determine whether autoclaving of pipette tips would influence the pipetting result. Recent scientific literature reported evidence of disturbance of a broad range of biological assays caused by leachables, even for pipette tips [1, 2]. Examples include enzymatic and photometric assays as well as alterations in growth rates in cell culture [3]. Eppendorf does not make use of such additives and provides certificates to this effect. However, in order to obtain experimental proof, we have tested Eppendorf pipette tips for inhibition effects on the development of early stage embryos by performing a Mouse Embryo Assay. Materials and methods Autoclaving was performed by applying standard methods [4]. The influence of autoclaving on the performance of pipette tips by different manufacturers was determined by calibration [4] with the Eppendorf Xplorer® pipette. The MEA test was performed by an accredited and FDA-registered laboratory [4]. MURIEL ART, VINCENT DUFEY, ION GLIGOR, EPPENDORF APPLICATION TECHNOLOGIES S.A., NAMUR, BELGIUM ULRIKE GAST, LAURA KOCH, RONJA KUBASCH, EPPENDORF AG, HAMBURG, GERMANY Results and discussion Autoclaving is a widely applied method for the decontamination of labware such as pipette tips. Thus, one would expect autoclaving to have no impact on the tip’s performance. On the contrary, Fig. 1 shows that autoclaving did exert a negative influence on the performance of the tips by manufacturers B, D, and I. Indeed, the system of pipette and tip passed calibration with tips by these manufacturers prior to autoclaving but exceeded the permissible error limits for the systematic error at 1 μL after autoclaving. For the production of good tips, the impact of autoclaving is already taken into account during the construction phase. The type of polypropylene (PP) and the shape and surface structure decide how much a tip will shrink and in which direction this will occur. Recycled materials typically contain higher concentrations of leachables, Systematic error – 1 μL S ys te m at ic e rr or [ % ]