A portable analyser for the measurement of ammonium in marine waters

• Published in: Environmental science--processes & impacts Vol. 15; no. 3; pp. 579 - 584
• Main Authors: Amornthammarong, Natchanon, Zhang, Jia-Zhong, Ortner, Peter B, Stamates, Jack, Shoemaker, Michael, Kindel, Michael W
• Format: Journal Article
• Language: English
• Published: England 01.01.2013
• Subjects: Environmental Monitoring - economics; Environmental Monitoring - instrumentation; Equipment Design; Fluorometry - economics; Fluorometry - instrumentation; Fresh Water - analysis; Quaternary Ammonium Compounds - analysis; Seawater - analysis; Sensitivity and Specificity; USA, Florida
• ISSN: 2050-7887; 2050-7895
• DOI: 10.1039/c2em30793f

A portable ammonium analyser was developed and used to measure in situ ammonium in the marine environment. The analyser incorporates an improved LED photodiode-based fluorescence detector (LPFD). This system is more sensitive and considerably smaller than previous systems and incorporates a pre-filtering subsystem enabling measurements in turbid, sediment-laden waters. Over the typical range for ammonium in marine waters (0-10 μM), the response is linear ( r 2 = 0.9930) with a limit of detection ( S / N ratio > 3) of 10 nM. The working range for marine waters is 0.05-10 μM. Repeatability is 0.3% ( n = 10) at an ammonium level of 2 μM. Results from automated operation in 15 min cycles over 16 days had good overall precision (RSD = 3%, n = 660). The system was field tested at three shallow South Florida sites. Diurnal cycles and possibly a tidal influence were expressed in the concentration variability observed. A portable ammonium analyser was developed and used to measure in situ ammonium in the marine environment.