65 25 4 the yellow band which developed on the plate rf 0 38 which could also be detected under both long and short uv light was stripped from the plate and eluted with the same solvent system the eluent so produced was evaporated and the residue of the evaporation triturated with methanol to form a mixture this mixture was then filtered through a polycarbonate membrane 13 mm diameter 0 2 um pore size nucleopore corp pleasanton calif mounted on a syringe filter holder and the filtrate so produced was evaporated to give dmae ams 15 mg 62 a solution of 2 39 6 39 dimethyl 4 39 carboxylphenyl 10 methyl acridinium 9 carboxylate bromide dmae cooh 18 mg 0 038 mmole in 3 6 ml of a dioxane water 1 1 mixture was treated with 1 3 dimethylaminopropyl 3 ethylcarbodiimide hydrochloride 37 mg 0 193 mmole aldrich chemical co inc milwaukee wis at room temperature for 5 minutes to form a reaction mixture a solution of 7 amino 1 3 naphthalenedisulfonic acid ands 26 mg 0 076 mmole aldrich chemical co inc in 0 9 ml of water was added to the reaction mixture which was then stirred at room temperature overnight and evaporated the residue of the evaporation was dissolved in a minimal amount of 0 1m sodium carbonate to obtain a solution at neutral ph this solution was mixed with an equal amount of methanol and purified on a 20 u00d7 20 cm preparative tlc plate silica gel 60 f254 merck amp co inc and developed with chloroform.