T 1521 (OTTO) Tetra phenyl phosphonium bromide, 98% Cas 2751-90-8 - used for the detection, identification, analysis, etc. of chemical, biological, or pathologic processes or conditions. T 1521 (OTTO) Tetra phenyl phosphonium bromide, 98% Cas 2751-90-8 - used to extract heavy metals from aqueous solution as ion-association complexes.