“…In addition, PED at a gold electrode has proven to be selective for sulfur-containing compounds under mildly acidic conditions [10,19,20]. The use of PED following HPLC has been applied to methionine [20,21], glutathione oxidized/reduced [10,22], cysteine [21,22], homocysteine [21,23], antibiotics including penicillins and cephalosporins [11,[24][25][26], and other reduced and oxidized sulfur-containing compounds.…”