| abstract |
A marker composition comprising a marker substance that is: wherein any one of the hydrogen atoms can be replaced by deuterium atoms; ring A contains zero to two substituents, X and Y, where X and Y are independently any substituent that does not confer significant solubility in water to the molecule or are an N-alkyl sulfonamide group; R1 and R2 are, independently of each other, hydrogen, deuterium or a substituted hydroxy group; and R3 is an alkyl, alkoxy or acylamino group. |