Configuration with internally coupled valves to overcome shortcomings in the simultaneous determination of nitrite and nitrate by flow-injection analysis

A configuration with internally coupled valves and a reductant column located in the loop of the secondary valve is proposed for the simultaneous determination of nitrite and nitrate. Depending on the column characteristics, a washing stream flowing in the opposite direction to the sample may or may not be required. The washing step may conveniently be performed by use of the proposed configuration.