Selective determination of ammonium in water based on HPLC and chemiluminescence detection

A selective and sensitive method has been developed for liquid chromatographic determination of ammonium in water samples. The analyte is derivatized with Dansyl Chloride prior to injection into HPLC. Optimal solution derivatization conditions have been established. The dansyl derivative is separated with the aid of a chromatographic column and post-column mixed with peroxyoxalate (TCPO) and H2O2 in order to perform chemiluminescence detection. The detection limit achieved is 8 μg/L and linear response from 0.027 to 0.750 mg/L of ammonium was obtained. Ammonium ion was determined within 2.4 min under optimum chromatographic conditions. The method is fast, and near 10 derivatized samples can be measured per hour. No interference of amines has been obtained. Accuracy studies gave % relative error below 9.8%, and precision studies gave %RSD between 2 and 8%. The method can be applied for amine and ammonium screening and quantification of ammonium in different kind of water samples: bottled, tap, lake, fountain, irrigation, waste and sea. Matrix effect was only found in seawater samples. The method was also applied to several samples after applying Kjeldahl treatment in order to obtain values of total Kjeldahl nitrogen.