A volume of 25 mL H2SO4 (2.5 mol L-1) was added to 0.50 g of EP — (CH2)3-SH and stirred at room temperature. After 1 h, the solids were fil­tered and washed thoroughly with water and acetone. Finally, the material was dried at 90 °C for 16 h under vacuum (~0.1 Pa) and referred to as EP-(CH2)3-SO3H.

9.3.2 DETERMINATION OF THE AMOUNT OF REACHABLE THIOLS

A titration is performed as described in the literature [44]. A solution of silver nitrate with a known concentration is added to 0.050 g of material

and left to stir until the equilibrium is reached. The excess of silver is ti­trated with potassium thiocyanate and FeNH4(SO4)212H2O in 0.3 mol L-1 HNO3 as indicator.