Abstract Some new 9-substituted 10-methylacridinium trifluoromethanesuifonate (triflate) salts have been synthesized and shown to react in methanol with the model aromatic and aliphatic amines, aniline and n-butylamine, to form derivatives which absorb strongly at 445 and 439 nm, respectively. The color development is affected by heat and heating time and by the quantity of acridinium triflate used. A 10–50-fold molar excess of the triflate should be used and the solution heated at 60° for 30 min. The linearity and reproducibility of the assay are improved by the presence of pyridine (for aniline) and triethylamine (for n-butylamine) in the reaction mixture. Beer's law is obeyed over the range 0–1860 ng/ml for aniline and 0–1440 ng/ml for n-butylamine, with each of the new reagents. The relative error and the precision of determination depends on the acridinium triflate used.