I've been conducting RNA extraction from 500 microliters of whole blood using the Purelink RNA Minikit according to the provided instructions. Despite several attempts, I'm consistently obtaining low yields (less than 20ng) with poor quality, indicated by a low 260/230 ratios. The blood is clogging the kit membrane. Unfortunately, I'm unable to switch to a different kit at the moment. Could someone please give me some advice on how to improve both the yield and quality of my RNA extraction and without clogging the filter and switching to the organic method.