Flow Injection Tutorial

Since the Cd/Cu column is the key component of this assay its efficiency to reduce nitrate to nitrite was evaluated first. This was done by comparing responses obtained with nitrate and nitrite samples of the same concentration (100ppB N ). Comparison of blank, nitrate and nitrite responses (run in duplicate) show that this column had 80% efficiency (A). While this is

satisfactory, it will be shown below that up to 98% efficiency can be obtained by regenerating the surface of Cd/Cu particles.

The influence of contact time (B) between nitrate and Cd/Cu reveals is no appreciable gain between efficiency at 0 and 10 sec stop time as defined by software script. (There is, actually about 3 sec period when sample is in contact with Cd/Cu at 0 WAIT of software script, because reagent aspiration into holding coil takes some time, see D on the previous page

The influence of sample volume retrieved from the column (C) follows the usual pattern as known for SI based assays.