I try to isolate small RNA from 400ul plasma by using NucleoZOL reagent by Macherey Nagel in order to send them for sequencing.

The requirements for the sequencing procedure are A260/280 >2, A230/280 > 2, around 200ng quantity.

As you can see in the following table I isolated one plasma sample and a DNase/RNase free H2O that I treated as a contamination marker.

The problem is that both my extracted H2O and plasma sample have the same concentration. Considering possible contamination I measured OD from the same samples after extraction in a closed system extraction machine (table 2).

As you can see I had the same problem. Does anyone have an idea about this?