Store kits away from light. Keep reagent bottles inside kit during storage. When performing tests, do not leave reagent containers open any longer than necessary. When replacing or refilling sunlight- sensitive reagents, be sure to place them in opaque bottles. Air decomposition Air is the enemy of several reagents.
Evaporation can concentrate reagents, which is especially critical for a titrant.
Also, many reagents can react chemically with oxygen or carbon dioxide in the air. For example, the manganese reagent used in the dissolved oxygen test reacts with oxygen. Keep reagent bottles tightly capped. Contamination Contamination is probably the biggest enemy of monitoring kits. Any foreign material introduced into a reagent bottle can cause test results to be too high or too low.