Chemiluminescent acridinium salts by virtue of their high quantum efficiency can be detected at the attomole (10-18 mol) level and below1 and thus have recently been used as labeling reagents for ultrasensitive clinical assays. 2 The N10-methyl derivatives have generally been employed and are efficiently prepared by quarternization of the acridine precursor with methyl fluorosulfate or methyl triflate; poor conversion is seen with ...