Used cartridges should be cleaned, rinsed and impregnated before storage with one of the following preservative solutions.
• Glycerin @ 80 – 100% (best)
• Phosphoric acid @ pH 2 – 3
• Benzoic acid or sodium benzoate @ 1,000 ppm
• Sodium bisulfite or sodium metabisulfite @ 1,000 – 5,000 ppm
Stored cartridges should be inspected at least once per month for loss of preservative solution or growth of microorganisms.