I’m having issues with the stability of ATP. My lab has purchased multiple brands of ATP (Sigma # A6419; SantaCruz #SC-202040), each of which seem to come hydrolyzed. My lab uses the Malachite green assay to detect inorganic phosphate. Immediately upon preparation of ATP (creating a 10mM stock by dissolving the powder in UltraPure water), the ATP has been tested using Malachite green. Results showed inorganic phosphate levels roughly 10-15X higher than expected and as measured in water and all other reagents used for this assay. The instability and hydrolysis of ATP has resulted in background noise so high, we cannot determine differences between samples when running the assay. Our lab has historically used the Sigma ATP and did not have issues until last year. Has anyone else been experiencing this? Is there other brands that have more stable products, is there other methods of preparation that increases the stability?