FAQ - Test Kit Storage & Stability

Most components should be stored cold and dark. NADH and enzyme (AtNaR, YNaR) are sensitive to oxidizing agents — use clear glass, polypropylene (PP), or polyethylene (PE) tubes and vials for storage.

See the individual component questions below for specific storage requirements for each part of the kit.

Enzyme packs contain the enzyme and NADH, freeze-dried in cuvettes and containers, then vacuum-sealed in foil pouches. All kits carry a 6-month expiration date, but packs consistently remain stable well beyond 6 months when stored at any temperature below 22°C. Stability study samples have remained effective even after multiple years.

For maximum longevity, store enzyme packets at -20°C — the enzyme can remain stable for years under these conditions.

The 6-month expiration date applies from the time of purchase, not from when the pouch is opened. Once opened, packs remain stable for more than 6 months when stored below 22°C, and can last for years when stored at -20°C.

Once the kit process has been started, aim to complete it the same day. Do not let prepared solutions sit for extended periods.

NADH oxidizes to NAD+ over time and will eventually be unable to supply the electrons needed for the nitrate reduction step. To maximize its useful life, portion NADH into small aliquots — approximately the volume you would use in a single day's work.

Store aliquots in the fridge for at least one week, or frozen for up to one month. You may see longer activity retention, but one to two weeks refrigerated is a safe working guideline.

The assay buffer is stable for one month when stored cold.

Both Color Reagent 1 and Color Reagent 2 are stable for up to one month when stored cold (at or below 4°C) and dark.

Color Reagent 2 (NED reagent) will begin to turn brownish after several weeks once water has been added. This causes a loss in sensitivity as the background in blanks becomes too high — this is a sign the reagent should be replaced.

Once you begin the kit process, aim to complete it the same day. Follow stated times carefully — do not let prepared solutions sit for extended periods. The most common errors are either stopping the reduction reaction too soon, or not proceeding to the next step in time.

Keep all components cold and sealed until use. Do not open or reconstitute any component until you are ready to use your kit.

In freeze-dried form, PNP is stable for months when stored at -20°C or colder. Once reconstituted, PNP should be used the same day.

In freeze-dried form, MESG is stable for months when stored at -20°C or colder. Once reconstituted, MESG should be used the same day.

The phosphate kit buffer is stable for months when stored at 4°C. Do not open it until you are ready to use it.