Dissolved free amino acids DFAAs and ammonium are important nutrients in marine microbial food webs. DFAA concentrations are most often studied by high-pressure liquid chromatography of fluorescent derivatives with o-phthaldialdehyde OPA. This procedure is laborious, requires extensive sample handling, and yields results hours or days after sampling. A fluorescent monitoring system for DFAAs, other primary organic amines, and ammonium was developed that is automated and continuous, and provides results in real-time. A gently pumped stream of seawater is reacted with an OPAmercaptoethanolbuffer reagent and passed under the tip of a fiber optic probe supplying excitation light below 400 nm. The fluorescent signal, with a maximum at 455 nm, is transmitted by the probe to an optical multichannel analyzer employing a linear photodiode array. A plot of fluorescent intensity vs. time is recorded. The signal is linear in the range 1 to 100 nM alanine equivalents. Keywords Food chains DD1473 only.
Rept. for period ending Jan 88,
Presented at the American Geophysical Union, Ocean Sciences Meeting, New Orleans, LA, 18-22 Jan 88.