A simple,rapid and reliable gas-diffusion flow injection(GD-FI) method for ammonium determination in
building materials has been developed.It is based on leaching ammonium from a ground solid sample into
an alkaline solution with subsequent ammonia gas generation. Ammonia is then transported in a nitrogen
stream to the GD cell of the FI system where it is absorbed into its acceptor solution containing a mixture of
the acid–base indicators cresol red and thymolblue. The maximum increase in the absorbance of the
acceptor solution at 580 nm is related to the ammonium concentration in the solid sample. The proposed
method is characterized by alinear concentration range of 0.1–5.0 mg NH4 + kg-1, alimit of detection of
8 μg NH4 + kg1 and a sample throughput of 10 h-1. A successful application of this method for the deter-
mination of ammonium in building materials such as concrete, cement and sand is reported.