Formaldehyde, polymer with benzenamine, hydrogenated

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1997

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Guideline study (GLP)

Qualifier:

according to guideline

Guideline:

EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Radiolabelling:

no

Analytical monitoring:

yes

Buffers:

pH 4 buffer (preliminary and test 1)
Potassium dihydrogen citrate (69.03 g) was dissolved in distilled water (3000 ml) and the pH of the solution adjusted to 4.00 with 1M aqueous
sodium hydroxide at ambient temperature. After Dissolution was aided by placing the flasks in an ultrasonic bath and once the contents dissolved,
the solutions were transferred to 50 ml crimp top bottles. Samples were taken for analysis at 0 hours and at two other time points after 30%
hydrolysis had occurred and cooled in an ice water bath for 1 minute prior to analysis.autoclaving, this solution was stirred and heated on a
magnetic stirrerhotplate and the pH measured as 4.01 with the temperature of the buffer solution at 50°C + 0.5OC.
pH 4 buffer (test 3)
Potassium dihydrogen citrate (46.16 g) was dissolved in distilled water (2000 ml) and the pH of the solution adjusted to 4.00 with 1M aqueous
sodium hydroxide at ambient temperature. The buffer solution was then equally divided into separate containers to enable the test to be carried out at 60 and 70°C. AfCer autoclaving, these solutions were stirred and heated on a magnetic stirrer/hotplate and the pH measured as 4.00 with the
temperature of the buffer solution at 60°C t- 0.5"C and as 4.00 with the temperature of the buffer solution at 70°C k 0.5"C.
pH 7 buffer
Potassium dihydrogen orthophosphate (40.80 g) was dissolved in distilled water (3000 ml) and the pH of the solution adjusted to 7.00 with 1 M
aqueous sodium hydroxide at ambient temperature. The solution was stirred and heated on a magnetic stirrer/hot plate and the pH measured as
7.01 with the temperature of the buffer solution at 50°C rt 0.5 OC
pH 9 buffer
Potassium chloride (23.14 g) and boric acid (18.62 g) were dissolved in distilled water (3000 ml) and the pH of the solution adjusted to 9.00 with
1M aqueous sodium hydroxide at ambient temperature. This solution was stirred and heated on a magnetic stirrerlhotplate and the pH measured as 9.00 with the temperature of the buffer solution at 50°C i: 0.5"C.

Details on test conditions:

Prior to the test, nine 50 ml volumetric flasks and nine 50 ml crimp top bottles were rinsed with ethanol and allowed to drip dry. The buffer
solutions were autoclaved at 1 11 OC for 21 minutes and then purged with nitrogen for 15 minutes prior to use. Test substance (ca 0.05 g) was
accurately weighed into each of the volumetric flasks. The flasks were diluted to volume with the appropriate buffer solutions at room temperature.Duplicate solutions at each pH value were prepared. Dissolution was aided by placing the flasks in an ultrasonic bath and once the contents had
dissolved the solutions were transferred to 50 ml crimp top bottles. After 2.4 hours and 5 days a further aliquot (ca 10 ml) of each solution was
taken and cooled in an ice water bath for 1 minute prior to analysis.
PERFORMANCE OF TEST 1 AT pH 4
Prior to the test, three 50 ml volumetric flasks and three 50 ml crimp top bottles were rinsed with ethanol and allowed to drip dry. The buffer
solutions were autoclaved at 11 I0C for 21 minutes and then purged with nitrogen for 15 minutes prior to use. Into each of the volumetric flasks,
test substance (ca 0.05 g) was accurately weighed. The flasks were diluted to volume with pH 4 buffer solution at room temperature. Duplicate
solutions were prepared. Dissolution was aided by placing the flasks in an ultrasonic bath and once the contents had dissolved the solutions were transferred to 50 ml crimp top bottles. At various time intervals (chosen to obtain data points suitable for reaction rate calculation), further
aliquots (ca 10 ml) were taken and cooled in an ice water bath for Iminute prior to analysis.
PERFORMANCE OF TEST 3 AT pH 4
Prior to the test six 50 ml volumetric flasks and six 50 ml crimp top bottles were rinsed with ethanol and allowed to drip dry. The buffer solutions
were autoclaved at l l 1°C for 21 minutes and then purged with nitrogen for 15 minutes prior to use. Into each of the volumetric flasks, test
substance (ca 0.05 g) was accurately weighed. The flasks were diluted to volume with the pH 4 buffer solutions at room temperature. Duplicate
solutions were prepared, for each temperature. Dissolution was aided by placing the flasks in an ultrasonic bath and once the contents dissolved, the
solutions were transferred to 50 ml crimp top bottles. Samples were taken for analysis at 0 hours and at two other time points after 30% hydrolysis
had occurred and cooled in an ice water bath for 1 minute prior to analysis.

Number of replicates:

2 test series with dublicates

Positive controls:

yes

Remarks:

Three 50 ml crimp top bottles containing buffer only (one at each pH) were placed in the 50°C water bath along with the test solutions. These solutions were then taken through the same procedure as the test solutions prior to analysis.

Statistical methods:

by extrapolation using linear regression of log10, Kobs versus reciprocal temperatures in degrees K (see Arrhenius equation). The log of the rate
constant (log10, kobs) at 25°C was calculated as -3.4373 yielding rate constant (Kobs) of 3.6536 x.10e-4

Preliminary study:

PRELIMINARY AND TEST 1
Calibration data are given in Table 1 and show that a linear response of peak area versus
concentration was obtained on each occasion of analysis (except Test 1, pH 4 at 33 days). Analytical
data are given in Tables 4 and 5 showing that at pH 7 and 9 less than 10 % hydrolysis occurred and at
pH 4 greater than 10 % hydrolysis occurred over five days at 50°C

Transformation products:

no

% Recovery:

70.5

pH:

4

Temp.:

60 °C

Duration:

4 d

% Recovery:

79.8

pH:

4

Temp.:

60

Duration:

6 d

% Recovery:

47.1

pH:

4

Temp.:

70

Duration:

2 d

% Recovery:

71.9

pH:

4

Temp.:

70

Duration:

2 d

% Recovery:

13.6

pH:

4

Temp.:

50 °C

Duration:

2 d

% Recovery:

29.3

pH:

4

Temp.:

50 °C

Duration:

3 d

% Recovery:

31.9

pH:

4

Temp.:

50 °C

Duration:

7 d

% Recovery:

36

pH:

4

Temp.:

50 °C

Duration:

9 d

% Recovery:

72

pH:

4

Temp.:

50 °C

Duration:

33 d

pH:

4

Temp.:

50

DT50:

79 d

Details on results:

Determination of the reaction order at pH 4 and 50°C shows that hydrolysis is pseudo first order, requiring Test 3 to be performed either at two temperatures above 50°C differing by 10°C, or at 25°C with analysis at t = 0 and then at two time-points where the degree of hydrolysis is greater than 30 %.
TEST 3 - DETERMINATION OF RATE CONSTANT AND HALF-LIFT AT pH 4 60°C and 70°C.
Calibration data are given in Table 1 and show that a linear response of peak areas versus concentration was obtained on each occasion of analysis.
Analytical data for pH 4 hydrolysis at 60 C and 70°C are given in Table 6
Plots of log,, percent remaining versus time show straight lines. The slope of each line was calculated by linear regression analysis. The rate constants were determined pH4, 60 C, log10 rate constant = - 1.9544 pH4, 70 C, log10 rate constant= -1.5861 The rate constants at 25OC for pH 4 was found by extrapolation using linear regression of log10 kobs versus reciprocal temperatures in degrees K (see Arrhenius equation). The log of the rate constant at 25°C was calculated as -3.4373 yielding rate constant (Kobs) of 3.6536 x lo4. The rate constant values obtained at 25°C were then used to calculate the hydrolytic half-life time for pH 4 solution using the appropriate equation (given on page 16).
The half-life time was: pH 4 t ½ (25°C) = 79 days.

Validity criteria fulfilled:

yes

Conclusions:

The half-life of MPCA has been determined at pH 4, 7 and 9. At pH 7 and 9, the half-life has been determined to be greater than one year at 25OC and at pH 4 the half-life of MPCA at 25OC was determined to be 79 days

Executive summary:

The half-life of MPCA has been determined at pH 4, 7 and 9.

At pH 7 and 9, the half-life has been determined to be greater than one year at 25°C

and at pH 4 the half-life of MPCA at 25°C was determined to be 79 days

Description of key information

At pH 7 and 9, the half-life has been determined to be greater than one year at 25°C and at pH 4 the half-life of MPCA at 25°C was determined to be 79 days.

Key value for chemical safety assessment

Half-life for hydrolysis:

1 yr

at the temperature of:

25 °C

Additional information

The hydrolysis half-life of Formaldehyde, polymer with benzenamine, hydrogenated has been determined at pH 4, 7 and 9.

At pH 7 and 9, the half-life has been determined to be greater than one year at 25°C.

At pH 4 the half-life at 25°C was determined to be 79 days.