Palintest Oxystop removes Potassium Monopersulfate interference, from Combined (total Chlorine) tests. Suitable for use with Extended Range Photometers. The DPD Oxystop tablet is added after measurement for free chlorine DPD-XF but before the DPD-XT tablet. It prevents the reaction between shock treatment chemicals and potassium iodide which would give a positive response.