9521618 GREEN A continuous flow analyzer powered by osmotic pumps has been developed to monitor nitrate concentrations while submerged in freshwater or seawater. Osmotic pumps driven by a NaCl gradient propel both sample and reagents through a miniature continuous flow manifold. The analyzer operates with sample and reagent flow rates of about 8.0 and 0.7 ml per month, respectively, shows a linear response from 0 to 20 micromolar nitrate with a detection limit of 0.1 micromoles, and has a 90% response time of approximately 30 minutes. The analyzer automatically standardizes itself by correcting for baseline and sensitivity drift by periodically injecting and analyzing known standard solutions. The system has operated continuously for month-long periods in freshwater and seawater, and can be adapted to a variety of colorimetric analyses. The research supported here will take this demonstrated technology and develop the chemistries to analyze for a variety of trace metals (i.e., iron, zinc, cadmium, copper and manganese), as well as other macro-nutrients (i.e., silica and phosphate). Potential applications for such analyzers include oceanographic studies as well as environmental monitoring and industrial process control.
