Carrier Solution:

When carrying out high-sensitivity analysis, such as below 100 nM, the Carrier solution should be used within one week of preparation. For less sensitive detection, it can be stored for up to one month. If the solution is used daily, it is not necessary to keep refrigerated overnight. In the case that the solution will be used less frequently, over the course of a month, it is better to store refrigerated. Please note: the Carrier solution should never be applied to the ENO-30 when cold. Always allow it to warm to room temperature before use. Cold solution may cause generation of air bubbles in the pumps.

If the carrier is contaminated with nitrite and its level is more than the samples, the peaks of nitrite and nitrate given by the samples will be negative peaks (dips).  

Reactor Solution:

Reactor solutions A and B can be stored refrigerated for up to one month in separate bottles. Storage should be in an airtight glass container, covered with tinfoil to keep out light. The required amount of the working Reactor solution (50% A + 50% B) should be prepared fresh daily, also in a glass container covered in tinfoil. If the solution is exposed to light and/or reacts with atmospheric NO2, it acquires a red coloration. In such case it becomes unsuitable for use. For this reason it may be more suitable to use clear glassware, to check for signs of such discoloration. (As with the Carrier, the Reactor solution should never be applied to the ENO-30 when cold.)