A portable battery-powered flow injection monitor for the in situ analysis of nitrate in natural waters

The design and performance of a portable, automated flow injection (FI)-based photometric monitor are described. The system is controlled by an in-house microcomputer system that enables the monitor (including a solid state detector) to operate from a 12 V battery supply. The monitor uses the cadmium reduction/diazotization method to analyse for nitrate with a linear range of 0 to 12 mg l(-1) and a limit of detection of 0.05 mg l(-1) (NO(3)-N). The hardware and software design, monitor performance and results obtained during unattended operation are presented.