Phthalaldehyde Reagent

Dissolve 2.47 g of boric acid in 75 mL of water, adjust the pH to 10.4 with a 45% w/v solution of potassium hydroxide and add sufficient water to produce 100 mL. Dissolve 1.0 g of phthalaldehyde in 5 mL of methanol, add 95 mL of the boric acid solution and 2 mL of mercaptoacetic acid and adjust the pH to 10.4 with the potassium hydroxide solution.

Store protected from light and use within 3 days of preparation.