# Illumina RNA Prep Tagmentation (L) with Enrichment Input FAQs
**What is the RNA input requirement?**
The protocol is optimized for 10-100 ng of purified total RNA. Lower input amounts can reduce library yield.
**Is the kit compatible with RNA from FFPE samples?**
Yes, for FFPE samples with DV200 value <80% Illumina recommends increasing the number of PCR cycles to 17.
**What are the optimal 260/280 and 260/230 ratios for the input RNA?** (Refer to the first informational row, the second and third are provided for context.)
Substance
Absorbance (nm)
260/280 Ratio
260/230 Ratio
Pure RNA
280
~2.0
2.0-2.2
EDTA, Carbohydrates, Phenol
230
<1.5
<2.0
Guanidine HCl
230
<1.5
<2.0
**What is the recommended quantitation method for input RNA?**
RNA should be quantified with a fluorometric method specific for RNA.
**Does input RNA need to be treated with DNase?**
Yes, DNA should be removed by including a DNase treatment with the RNA isolation method for sample purity and accurate quantification.
**What is the effect of residual DNA contamination?**
DNA can interfere with accurate quantification of the sample. DNA contamination will also impact the sequencing data, increasing the background level of expression for all transcripts.
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