A novel optoelectronic detector and improved flow analysis procedure for ammonia determination with Nessler's reagent

This paper presents a simple, rapid and effective method for ammonia determination in a flow analysis regime using Nessler's reagent. The proposed modification of the common flow procedure results in the total elimination of the problem of precipitate deposition inside the flow manifold. The improved procedure has been adapted to a flow analysis system based on microsolenoid pumps combined with a dedicated optoelectronic detector fabricated specifically for this purpose. This photometric device has been constructed in the form of a compact flow-through cell (70 μL total volume and 1 cm optical pathlength) integrated with 395 nm LED emitter and 405 nm LED-based detector. The presented analytical system is capable of ammonia determination in the submillimolar concentration range with a detection limit below 0.1 mM and high throughput (over 20 injections per hour).