Purification of Acridine Orange
The double salt with ZnCl2 (6g) was dissolved in water (200mL) and stirred with four successive portions (12g each) of Dowex-50 ion-exchange resin (K+ form) to remove the zinc. The soln was then concentrated in vacuum to 20mL, and 100mL of ethanol was added to ppte KCl which was removed. Ether (160mL) was added to the soln from which, on chilling, the dye crystallises as its chloride. It was separated by centrifuging, washed with chilled ethanol and ether, and dried under vac, before being recryst from ethanol (100mL) by adding ether (50mL), and chilling. Yield 1 g.
Acridine Orange (CAS NO.494-38-21) was recrystd twice as the free base from ethanol or methanoYwater by dropwise addition of NaOH (less than 0.1M). The ppte was washed with water and dried under vacuum. It was dissolved in CHCl3 and chromatographed on alumina: the main sharp band was collected, concentrated and cooled to -20 °C. The ppte was filtered, dried in air, then dried for 2h under vacuum at 70 °C.