A separate activation treatment of 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) prior to the TEMPO mediated pulp oxidation and novel titration method of oxidized TEMPO (TEMPO+) is introduced. A separate TEMPO activation takes place under both concentrated and neutral (pH) conditions. The formation of TEMPO+ was verified by a novel titration method. The new method provides useful information on the activation of the radical TEMPO excluding activation with HOBr which interferes the titration. The oxidation of pulp under slightly alkaline conditions (pH 8) takes place immediately after the addition of pulp and NaClO. A carboxylate content of 0.7 mmol COOH / g pulp was achieved by a 2.3 mmol NaClO / g pulp dosage with less than 3 hours reaction time.