Patent ID: 7074835

Claim:
A compound of formula (I): in which A is a C alkylene group with a chain length between NH and N(O)Râ€²Râ€³ of at least 2 carbon atoms and Râ€² and Râ€³ are each separately selected from C 1-4 alkyl groups and C 2-4 hydroxyalkyl and C 2-4 dihydroxyalkyl groups in which the carbon atom attached to the nitrogen atom does not carry a hydroxy group and no carbon atom is substituted by two hydroxy groups, or Râ€² and Râ€³ together are a C 2-6 alkylene group which with the nitrogen atom to which Râ€² and Râ€³ are attached forms a heterocyclic group having 3 to 7 atoms in the ring, wherein the compound is formulated so that upon dissolution in aqueous solution the pH of the solution is in the range of 5 to 9.