Spectrophotometric detection of ammonia/ammoniumin flow
analysis involving the use of acid–base in dicators has been successfully applied as an alternative to the Berthelot reaction .While this approach is cheaper in terms of the reagents used , produces
results much faster and does not need elevated temperatures , its
implementation requires the introduction of a highly selective
online GD [24–26] or pervaporation [27–29] separation step prior to
the analytical detection. In both membrane separation techniques
the sample is introduced into a donor stream where a volatile or
semi-volatile analyte or analyte that can be converted chemically
into volatile species is separated from the sample matrix containing
interferents by transferring it across a hydrophobic porous membrane into a static or flowing acceptor solution in direct contact with the membrane and containing suitable acid–base indicators [24]