The age of a reagent solution is extremely important to the effectiveness of the reaction in the coil.
Many laboratories, because of time and money constraints, store reagent solutions for long periods of time. For the most part this is acceptable, but there are a few exceptions and restrictions to this practice. NEVER store solutions containing surfactants longer than a few days at the most. This is a fact that we see supported easily by our internal QC testing practices. If solutions are not stored with surfactant they can usually be kept for long periods, some longer than others. The storage life of each solution should be well documented and understood clearly so that when troubleshooting a problem old solutions as a cause may be discounted.