We observed this as well when working with low-input RNA samples. We use 1 ul of 5ug/ul linear polyacrylamide to precipitate the RNA in 0.5 ml of isopropanol, flash-frozen in liquid nitrogen, and centrifuged 20 min at 20,000 x g.

I assessed the effect of linear polyacrylamide on the absorbance by comparing Tris 10 mM elution buffer with and without 1 ul of 5ug/ul linear polyacrylamide (in 8ul so 0.625ug/ul). I measured 3 times each sample to assess technical variability. Data from the IMPLEN photo spectrometer. See the picture enclosed. Once linear polyacrylamide is added, its biggest impact is on the 230 nm wavelength, explaining probably the low 260/230 ratio we see for RNA samples with low concentrations.

Johan Zicola Are you aware of any methods on how to remove the linear polyacrylamide impurity?