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Environmental fate & pathways

Hydrolysis

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Description of key information

Under the applied experimental conditions , no chemical reaction is occuring between water and DAPD.
Instead, DAPD is removed from the test solution by precipitation on the glassware.

Key value for chemical safety assessment

Additional information

Two studies are available that address the hydrolysis of DAPD. In a first study (Mao, 1996), performed according to EU method C7, the aqueous samples from the pH incubation tests were analyzed using HPLC in order to dertermine their parent compound levels (main constituents). Three buffer solutions (pH 4, 7 and 9) were used for the incubation and samples were collected after 0, 3, 5, 25, 50 and 119hrs (pH 4) and 0, 3, 5, 25, 50, 119, 359 and 719 hrs (pH 7 and 9). The half-life of the test substance, measured at the different pH 4, 7 and 9, was respectively 18.2, 281 and 248 hr. The study showed evidence of dissipation of test substance by virtue of disappearance of chemical from various buffer/pH conditions. Diphenylamine hydroxy compounds were found at very low levels, but could not be shown to directly result from degradation of the main constituents of DAPD.

A second hydrolysis study was conducted as a follow up to the above study (Incavo, 1997). The study did not follow any internationally accepted guideline, but was designed specifically to investigate what reaction, if any, occurs between DAPD and water over a 28 day period. The test protocol uses a micro-extraction technique with chloroform to recover and concentrate the organic substances - both DAPD constituents and their degradation products, if any - present in the water samples. The concentrated chloroform fractions are subsequently analyzed by GC/MS.

The analyses showed drops to 34 -39% of initial concentrations for the 3 main constituents of DAPD within 7 days and slight drops thereafter. No new substances were detected as DAPD disappeared from the aqueous solution. Rather, precipitates of all three main constituents of DAPD were found on the surface of glass flasks used for the studies. The dissipation rate of the test substance found in this test is consistent with the first study. Additionally, no evidence on the formation of any hydrolysis products was found.

The results from this second study indicate that no chemical reaction between DAPD and water is occurring under these experimental conditions and that mere physical precipitation on the glassware is taking place.