Elevated baseline above the upper marker on TapeStation traces can indicate overcycling (see the following online FAQ for further details: Are my libraries overcycled? If so, What should I do? ).
A carryover of Purification Beads (PB) can also result in a peak around and beyond the upper marker on TapeStation/ Bioanalyzer/ Fragment Analyzer traces. This can be avoided by taking care not to transfer any beads after the final elution.
A few tips to prevent bead carry-over:
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Leave approximately 2 µl of the eluate on the beads when removing the eluate for QC and sequencing (i.e., transfer only 15 – 17 μl of the eluate into a fresh PCR plate and do not try to transfer the complete sample, as this will lead to bead carryover).
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Put your samples once again on the magnet and incubate for 5 minutes.
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Transfer 15-17 μl of the supernatant into a fresh PCR plate.
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Put your samples once again on the magnet when taking an aliquot to run for QC on Tapestation/Bioanalyzer/Fragment Analyzer, or similar.