Abstract
An enzymatic method was applied to the determination of ammonia in natural water. A sample solution containing ammonia was mixed with a glutamate dehydrogenase (G1DH), reduced nicotinamide adenine dinucleotide phosphate (NADPH) and 2-oxoglutarate. The decrease in the absorbance intensity caused by the disappearance of NADPH by this reaction was measured at 340 nm. We report here the application of this enzymatic method to determine ammonia in seawater, lake water and river water and compare the enzymatic method with ordinary indophenol blue colorimetry.
There was a linear relationship (r2=0.999) between peak height and ammonia concentration over the range 0-29 μM. The low concentration of measurement was about 0.5 μM for a sample volume of 250 μl. The interference effect of amino acids and urea at concentrations of 50 mgl-1 was negligible. Good agreement was found between the enzymatic method and ordinary indophenol blue colorimetry.
