HEPES CAS:7365-45-9

103-76-4

1562-00-1

7365-45-9

The general procedure for the synthesis of 4-hydroxyethylpiperazineethanesulfonic acid from N-hydroxyethylpiperazine and sodium 2-hydroxyethylsulfonate is as follows: 0.5 mole of N-hydroxyethylpiperazine, 0.565 mole of sodium 2-hydroxyethylsulfonate, and 500 ml of methanol were added to a 1000 ml four-necked flask fitted with a refluxing condenser tube, and the condensation reaction was carried out under sufficient stirring. The reaction was first carried out at 50 °C for 2.5 minutes, then gradually heated to reflux and continued for 3.0 hours. The reaction was cooled after completion of the reaction to give a reaction mixture containing 4-hydroxyethylpiperazine ethanesulfonate. The yield of 4-hydroxyethylpiperazine ethanesulfonate was 93.6% as analyzed by high performance liquid chromatography. A 20 liter solution of 4-hydroxyethylpiperazine ethanesulfonate at a mass concentration of 15 wt% was diluted to 5 wt% with deionized water under stirring, followed by removal of sodium chloride by dialysis. Then the purified HEPES product was obtained by evaporation concentration, cooling crystallization and filtration. Finally, the product was washed once with anhydrous methanol and dried under vacuum to obtain purified HEPES.A sample of purified HEPES was dissolved and tested for purity, which showed a purity of 99.9%, a yield of 85.6%, a pH of 6.46, and a concentration of chloride ions of 6.8 μg/g.