Sodium hydroxide grade in library denaturation for NGS
The "molecular biology grade" is just a gimmick in many situations. The reagent grade NaOH is quite pure (≥98%). The usual impurities (major being Na2CO3; ~1%) are also chemically insignificant (See the Sigma-Aldrich products 1 and 2). For the product that you have, read the label for details. It should be more or less the same.

Just prepare your solution in MilliQ water and pass it through a 0.2µm filter.