CAS RN: 121-75-5

Stability / Shelf Life

Stable under recommended storage conditions.
Malathion is stable in aqueous solutions buffered to pH 5.26; the drug is hydrolyzed at pH less than 5 or exceeding 7.
Biological activity of malathion premium grade remains practically unvaried for 2 years if stored in upopened, undamaged original containers, in cool, shaded, well-ventilated area. Recommended 68-86 deg F (20-25 deg C) for good shelflife. Do not heat above 55 deg C. Above 100 deg C, decomposes rapidly and explosion may be induced.
Data provided by the registrant indicate that Fyfanon Technical (EPA Reg. No. 4787-5) is stable for up to 1 year when stored under warehouse conditions (20-23 deg C), although a small amount of isomalathion accumulated (increase from <0.01% to about 0.1%).
Various malathion wettable powder formulations were subjected to long term storage @ ambient temp & to accelerated storage under uniform pressure of 25 g/sq cm @ 54 deg for 24 hr. Two degradation products formed during storage differed in their concn. Results from studies using thin layer chromatography suggested that ester groups might not have suffered any degradation, but cleavage occurred at the P-S bond.
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