|Mixed Bead Resin ||BioRad cat# 143-6425
|Formamide|| J.T. Baker cat#4028-00
|pH paper|| VWR cat# EM-9590-3
- Transfer 100ml formamide to 250ml Erlenmeyer flask. Check pH.
- Add 5.0 gm of resin, add magnetic stir bar, cover flask and let stir.
IMPORTANT: Use smallest stir bar (12mm), if bar is too big, stirs rapidly and pH
If initial pH is less than 7.0, stir the resin for 45 minutes.
If initial pH is greater than 7.0, stir resin 60 minutes.
- Check the pH of the formamide after stirring. If the pH is greater than 7.0 proceed to
next step. If pH is less than 7.0, discard the formamide and start again with fresh
bottle of formamide
- Filter sample through 0.2 um nylon filtration unit (Nalgene, cat# 153-0020 or 151-
5020 or Corning cat# 430771 or 430773
- Store deionized formamide in aliquots at -20C in a non frost free freezer.
Use each aliquot only once - do not freeze / thaw the deionized formamide
**Acidic pH produces data with low signal**
Different bottles of formamide even if bought at same time, from same supplier may have
different pH. Need to check pH for each bottle prior to deionizing.
Once add resin, pH will immediately increase to ~ 9.0, as resin stirs with formamide,
pH begins to drop. Rate pH drops depends on starting pH. Slightly acidic formamide
will drop faster than pH of neutral to slightly alkaline.