AbstractAn amperometric enzyme electrode for the determination ofL‐glutamine was developed. The probe consisted of a platinum electrode that senses hydrogen peroxide produced from the reactions catalyzed by glutaminase and glutamate oxidase, which are co‐immobilized on a preactivated Immobilon‐AV Affinity membrane. Protective membranes eliminated interferences fromL‐glutamate and most compounds electroactive at a similar potential. The response of the probe was linear over the concentration range 1 × 10−6M to 7.5 × 10−4M.L‐Glutamine in serum samples obtained from healthy volunteers was determined using the probe, and the results correlated well with previously