Lane mix and PhiX concentrations required for sequencing QuantSeq FWD-UMI libraries differ from those used for standard QuantSeq FWD libraries. This is related to the presence of the low-diversity 4 nt spacer immediately after the 6 nt UMI sequence. This low diversity spacer can impact read 1 quality over cycles 7 - 10 of the run. For this reason 5 – 30 % of PhiX should be spiked into all QuantSeq FWD lanemixes.
Optimal PhiX spike-in percentages also vary between instruments.
For full details please see the updated table in: https://faqs.lexogen.com/faq/Do-you-have-recommended-loading-concentrations-for-Lexogen-libraries-on-Illumina-sequencing-instruments%3F.226492417.html