n 1655 (OTTO) Nitrilotriacetic acid, 99% Cas 139-13-9 - used in complexometric titrations and as well as for protein isolation and purif ication in the His-tag method. n 1655 (OTTO) Nitrilotriacetic acid, 99% Cas 139-13-9 - used in sequestration of metals; chelometric analysis.