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EC number: 445-790-1
CAS number: 404362-22-7
Following the analysis of the initial standard and sample solutions, due
to excessive baseline drift associated with the high temperature program
required to elute the test material, the instrument analysis was
repeated for component 4 only using a column compensation. However, the
initial component 4 concentrations remained significantly lower than
anticipated based on the loading concentration and the percentage
recovery obtained during validation of the analytical method. Therefore
the percentage remaining after 120 hours incubation at 50.0 ± 0.5 °C has
been calculated from the theoretical as weighed concentration corrected
for the mean percentage recovery obtained at nominal concentrations of
5.0 and 2.5 mg/L.
Under basic conditions (pH 9) the two minor components, component 2 and
4 present at 4.7% and 4.0% respectively, were analysed as borderline to
the 90% remaining hydrolytic stability cut-off value. However a
half-life of greater than 1 year at 25OC was estimated based on:
i) The experimental variation in analytical concentrations were within
expectations of the method accuracy for the trace levels of the two
ii) At pH 9, the potential for adsorption onto the glassware was
maximised for the test material over the range investigated. This was
since the reduced ionization of the test material reduced the solubility
of the individual components. Secondly, under basic conditions the free
silanol activity, typically the site of adsorption, was maximised.
Therefore, although the flasks used for sample solution incubation were
treated with dimethyldichlorosilane to eliminate free silanol groups,
some potential for limited adsorption may have remained.
Therefore based on a maximum 12.1% reduction in test material
concentration, the increased percentage remaining for the more
significant components and the identification of a potential source for
the reduction in test material concentration, the half-life has been
estimated as greater than 1 year at 25 °C.
The hydrolytical stability of the test substance "MXDA/SM Adduct" was
determined under GLP and in accordance with EU Method C.7 in a
preliminary test at pH 4, 7 and 9 at a test temperature of 50 ± 0.5 °C.
Sample solutions were prepared in stoppered glass flasks at nominal
concentrations of the test material of 4 E-03 g/L in three buffer
solutions. Buffer solution for pH 4 contained 1.25 E-02 mol/dm3
potassium hydrogen phthalate, buffer solution for pH 7 contained 7.5
E-03 mol/dm3 disodium hydrogen orthophosphate (anhydrous), 5 E-03
mol/dm3 potassium dihydrogen orthophosphate and 5 E-03 mol/dm3 sodium
chloride and buffer solution for pH 9 contained 2.5 E-03 mol/dm3
disodium tetraborate and 5 E-03 mol/dm3 sodium chloride. The buffer
solutions were filtered through 0.2 µm membrane filters to ensure
sterile conditions and the solutions were subjected to ultrasonication
and degassing with nitrogen to minimise dissolved oxygen concentrations.
Sample solutions at pH 4, 7 and 9 were maintained at 50.0 ± 0.5 °C for a
period of 120 hours. Aliquots of the sample solutions were taken from
the flasks at various times and the pH of each solution recorded. The
concentration of the sample solutions was determined by gas
chromatography and the four main components of the test substance were
all detected with acceptable accurateness and recovery rates. Prior to
extraction each sample solution was adjusted to about pH 10.5 using 1.0
M sodium hydroxide solution. Duplicate aliquots were taken and extracted
with 3 x 30 mL dichloromethane. Each extract was filtered through
pre-washed separation paper, extracts were combined and evaporated to
dryness. Then the residue was re-dissolved in 10 mL acetonitrile.
Duplicate standard solutions at nominal concentrations of 40 mg/L were
prepared and sampled and analysed in parallel to the test solutions.
Less than 10% hydrolysis for compounds 1 to 3 was observed at 50 °C
after 5 days suggesting that these compounds had hydrolysis half-lives
of greater than 1 year at 25 °C and pH 4, 7 and 9. Analytical problems
due to excessive baseline drift associated with the high temperature
required to elute the test material made it necessary to re-analyse
component 4 only using column compensation. However, the initial
concentrations of component 4 remained significantly lower than
anticipated and the percentage remaining after 120 hours hence was
calculated from the theoretical as weighed concentration corrected for
the mean percentage recovery at nominal concentrations of 5 and 2.5 mg/L.
Under basic conditions at pH 9, the two minor components were analysed
as borderline to the cut-off value for hydrolytic stability (90% test
substance remaining after 120 hours at 50 °C). However, a half-life of
greater than 1 year at 25 °C was estimated for these two compounds
because experimental variation in analytical concencentration was within
the range expected from the method accuracy for the two trace compounds
and the potential adsorption onto glassware was maximised for the test
material over the range investigated. This was since the reduced
ionisation of the test material reduced the solubility of the individual
components and since the free silanol activity, typically the site of
adsorption, was maximised under basic conditions.
In conclusion, the estimated half-life at 25 °C for all four components
of the test material was greater than 1 year.
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