Purity: 88.7-108.4 g/L (Acetic Anhydride content, titration)
Other Notes: Cap A solution, containing acetic anhydride and tetrahydrofuran (THF), is used after the phosphoramidite reaction/coupling step. This solution aborts chains bearing unreacted 5'hydroxyl groups due to failure of reaction with activated phosphoramidite (typically, 1 to 2% of growing oligonucleotide chains in each synthesis cycle). These unreacted 5'hydroxyl groups are capped with an acetyl group and thus rendered unreactive for subsequent synthesis steps.