I use sodium tetraborate buffer. It never dissolves easily in water (10.0 mM, adjusted to pH 10.0 by 10.0 mM & 1.0 mM NaOH). It still look hazy. It is to be added to (OPA, Methanol and 2-Mercaptoethanol)
In Journal of Chromatography A, 1209 (2008) 70 - 75, they have used potassium borate buffer. The solubility of sodium tetra borate is not that good. Any comments