Howdy all!

I wanted to enquire as to the possible cause of magnetic bead contamination in final sample elution’s while using the ZymoBiomics MagBead RNA kit. We are doing many extractions in tandem on swabs following the recommended protocol; most of the samples come out fine, however some show inflated concentration readings and have a yellow tinge; i was told this is likely bead contamination. I also suspect this as often I will have issues with beads recurrently sucking into my pipette while aspirating off the final sample elution. When this happens I typically remix the beads and water and re-pellet the beads, however it seems to occur multiple times before I can prevent the beads from drawing into the pipette. It only happens occasionally, and I’m wondering if its user error on my part, or perhaps some oddity of the samples. I am not the only one performing these extractions, but it seems to occur more when I extract which makes me think I’m making some error. Some details;

The samples are swabs, and we believe they are stored in RNAlater rather than DNA/RNA shield (samples collected by someone else into incorrect storage buffer). We remove swabs into 750 ul DNA/RNA shield as per protocol. We are using a bead beater early in extraction as recommended in the protocol; post bead beating we transfer samples multiple times to reduce bead addition to the tubes to which we add magbeads.

We are extracting 24 samples at a time, which leads to some incubation steps running slightly longer for some samples. However there are no clear patterns regarding which samples play up.

Thanks for your time :)

James.