AMMONIUM DETERMINATION IN WINE BY GAS-PHASE MOLECULAR ABSORPTION SPECTROMETRY

A procedure for the determination of ammonium is described, based on i ts transformation into ammonia gas and subsequent measurement by UV-vi sible molecular absorption spectrometry at 194 nm. Two different proce dures for generating the ammonia are proposed, using NaOH solution and solid NaOH, respectively. After generation conditions for both proced ures had been optimized, better sensitivity was observed with solid Na OH. In these conditions, the method showed two ranges of linear respon se: from 1 to 100 mug and from 100 to 400 mug of ammonium. Finally, we determined ammonium in wine samples. Preliminary studies indicated th at the only observable interfering species was ethanol, which could be eliminated by subjecting the sample to vacuum evaporation until nearl y dry. This process also increased the sensitivity of the method by as much as ten times. The values obtained from three different wine samp les yielded results within the range of the concentration obtained by other authors. The recovery of ammonium added to the wine samples was around 95%.