Simultaneous Determination of Ammonia and Humic Acid in Natural Water by Chemiluminescence with Hypobromites

A simultaneous determination method for ammonia and humic acid in water based on the chemiluminescence method was developed. Ammonia was separated by a porous Teflon tube (in a double tube), and separated ammonia was reacted with hypobromite to produce chemiluminescence. By using the synergistic enhancement effect of humic acid for the chemiluminescence, a detection limit for ammonia of 0 . 41 μ mol dm −3 was obtained without any interference from other compounds. Humic acid in the remaining solution coming out from the double tube also reacts with hypobromite to produce chemiluminescence. Ammonia interfered with this chemiluminescence, but the effect was saturated at ammonia concentrations higher than 1 mmol dm −3 . The slope for the calibration graph of humic acid was not affected by ammonia concentration, but the value of the intercept for humic acid increased depending on ammonia concentration. There-fore, if the ammonia concentration is known, the humic acid concentration can be determined. The detection limit for humic acid was 1 . 1 ppb. The present method was applied to the measurement of natural water, and the results obtained by the present method were consistent with those obtained by ion chromatography for ammonia and another reported chemiluminescence method using N-bromosuccinimide for humic acid.