[0107] Furthermore, the accurate positioning of the pipette tip 71 by the guide elements 2 ensures that the sterile layer 16 is not pierced in multiple locations over the same well during multiple insertions of the pipette tip 71. This is an advantageous feature because a single experiment may include several hundred pipetting tip insertions over a single well, and multiple holes in the sterile layer 16 over the same well may increase the risk of contamination.