Reagent Shelf Life

All reagents have a shelf life, whether they are liquids, powders, crystals, tablets, or test-strip pads. If kept dry, powders and crystals are very stable; acids are also long-lived. Date of manufacture is not the controlling factor when it comes to shelf life—storage conditions are more important. As with all perishables, reagents are sensitive to environmental influences and will last longer under controlled conditions.

To this end, we recommend:

• Storing reagents at a consistent temperature in the range of 36°F–85°F (2°C–29°C); extreme temperature fluctuation, say from a refrigerator to a hot car trunk, causes reagents to deteriorate.
• Keeping them out of prolonged direct sunlight. (Note: Brown plastic bottles help protect very light-sensitive reagents.)
• Segregating reagents from containers of treatment chemicals.
• Replacing caps immediately and tightening them carefully so exposure to air and humidity is limited.
• Avoiding switching bottle caps, placing bottle caps on soiled surfaces, repouring reagents into contaminated containers, or touching test strip pads.

Taylor formulates its reagents to remain effective for at least one year, with only very few exceptions (molybdenum indicator in liquid form is one; after four months old it should be tested against a standard periodically). As a general precaution, replace all reagents more than one year old, or at the beginning of a new testing season.

For all of these reasons we advise users to carefully consider the container size when purchasing reagents. Larger bottles may appear to be the better value, but if you do not use them in a year’s time you may end up discarding reagent or risk exceeding the reagent’s useful life. Taylor’s dropper tips dispense 25 drops per milliliter. That means many tests requiring 5 drops of reagent per test will get 110 tests out of a .75 oz. bottle, or 300 tests out of a 2 oz. bottle. Homeowners should consider purchasing .75 oz. reagent bottles, while service professionals should probably be using 2 oz. bottles. Repouring from larger bottles (pints, quarts, or gallons) should be reserved for service companies with multiple technicians and retail stores doing high-volume testing. When repouring, it is best practice to replace the reagent’s dropper tip after approximately 8 refills.