Determination of ammonia in beers by pervaporation flow injection analysis and spectrophotometric detection

Abstract

A pervaporation flow injection (PFI) method is described for the determination of ammonia in beers. After injecting the sample into a NaOH donor solution, ammonia and other volatiles are transferred in the pervaporation unit from the donor stream to an acceptor stream containing sodium salicylate and nitroprusside, which subsequently mixes with alkaline sodium dichloroisocyanurate to allow the classical Berthelot reaction to take place. The blue-coloured complex formed is monitored spectrophotometrically at 655 nm. A linear calibration curve with a range of 0.1 40 mg l-1 was obtained. The method has a detection limit of 0.05 mg l-1 and is capable of a sampling frequency of 11 h-1 at 4 mg l-1..