There are two ways how to increase sensitivity of this assay:
- by extending the stop flow period
- by increasing light path of the flow cell
Increasing stop flow period to 34 seconds moved the calibration below 100 ppB range reaching 3 ppB N LOD, while the sampling frequency decreased to 60s/hr. (B).
Using 30 seconds stop flow period and extending the optical path, to 7 cm (using a PEEK made insert A) amplified , as one would expect, the absorbance 7 times, while the sampling frequency was 60 s/hr (C). It should be noted, however, that this is not necessarily an obvious result, since if the volume of the reaction mixture was less than the void volume of the extended flow cell (25 μL), five times amplification of absorbance would have not have been achieved. The expanded section of calibration C allows estimation of LOD to be 1.5 ppB N. (D)
High Sensitivity Nitrite Assay
1 to 100 ppB N 60 s/hr
2.2.16.
