1-Propanaminium, 2-hydroxy-N-(2-hydroxypropyl)-N,N-dimethyl-, esters with fatty acids, C16-18 (even numbered) and C18 unsatd., Me sulfates (salts)

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2013-04-03 to 2013-06-21

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Qualifier:

according to guideline

Guideline:

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

Qualifier:

according to guideline

Guideline:

EPA Guideline Subdivision N 161-1 (Hydrolysis)

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

- Name of test material: MDIPA-Esterquat C16-18 and C18 unsatd.
- Physical state: waxy solid
- Analytical purity: 100%

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

- Sampling intervals for the parent/transformation products:
preliminary test: t=0, t=5 days;
main study:
pH4, 20 °C: t= 0, 120, 217, 312, 333, 453, 553, 720 hours
pH4, 50 °C: t= 0, 2, 6, 70.5, 78, 94, 99.6, 118, 167, 245, 293, 407 hours
pH4, 60 °C: t= 0, 6, 23, 26.5, 29, 46.5, 29, 46.5, 50.5, 96, 168.5 hours
- Sampling method:
For each sampling time, duplicate sterile vessels under vacuum were filled with 6 ml test solution and placed in the dark in a temperature controlled environment at the appropriate temperature
- Sampling intervals/times for pH measurements:
The pH of each of the test solutions (except for the blanks) was determined at each sampling time.
- Sampling intervals/times for sterility check: no sterility check as sterile vessels and solutions were used, test was done in the dark
- Sample storage conditions before analysis: imediate analysis
- Other observation, if any (e.g.: precipitation, color change etc.): not reported

Buffers:

Acetate buffer pH 4, 0.01 M
solution of 16.7% 0.01 M sodium acetate in water and 83.3% 0.01 M acetic acid in water. The buffer contains 0.0009% (w/v) sodium azide.

Phosphate buffer pH 7, 0.01 M
solution of 0.01 M potassium di-hydrogenphosphate in water adjusted to pH 7 using 1 N sodium hydroxide. The buffer contains 0.0009% (w/v) sodium azide.

Borate buffer pH 9, 0.01 M
solution of 0.01 M boric acid and 0.01 M potassium chloride in water adjusted to pH 9 using 1 N sodium hydroxide. The buffer contains 0.0009% (w/v) sodium azide.

Isopropanol formate buffer mix
Solution of 50 mM ammoniumformate and 0.4% (v/v) formic acid in 94/6 (v/v) isopropanol/water.

Details on test conditions:

TEST SYSTEM
- Type, material and volume of test flasks, other equipment used:
xxxx

- Sterilisation method:
buffer solutions were filter-sterilised through a 0.2 µm FP 30/0.2 CA-S filter (Whatman, Dassel, Germany)

- Lighting:
For each sampling time, duplicate sterile vessels under vacuum were filled with 6 ml test solution and placed in the dark in a temperature controlled environment

- Measures taken to avoid photolytic effects:
placed in the dark

- Measures to exclude oxygen:
To exclude oxygen, nitrogen gas was purged through the solution for 5 minutes.

- Details on test procedure for unstable compounds:
no unstable compound

- Details of traps for volatile, if any
no volatile

- If no traps were used, is the test system closed/open
no volatile compound

- Is there any indication of the test material adsorbing to the walls of the test apparatus?
xxx

TEST MEDIUM
- Volume used/treatment
The buffer solutions were filter-sterilised through a 0.2 µm FP 30/0.2 CA-S filter (Whatman, Dassel, Germany) and transferred into a sterile vessel. To exclude oxygen, nitrogen gas was purged through the solution for 5 minutes. The test substance was spiked to the solutions at a target concentration of 0.5 mg/l using a spiking solution in isopropanol. Nominal concentrations were not corrected for the spiking volume (≤1%). For each sampling time, duplicate sterile vessels under vacuum were filled with 6 ml test solution and placed in the dark in a temperature controlled environment.

- Kind and purity of water:
Tap water purified by a Milli-Q water purification system (Millipore, Bedford, MA, USA)

- Preparation of test medium:
The buffer solutions were filter-sterilised through a 0.2 µm FP 30/0.2 CA-S filter (Whatman, Dassel, Germany) and transferred into a sterile vessel. To exclude oxygen, nitrogen gas was purged through the solution for 5 minutes. The test substance was spiked to the solutions at a target concentration of 0.5 mg/l using a spiking solution in isopropanol. Nominal concentrations were not corrected for the spiking volume (≤1%). For each sampling time, duplicate sterile vessels under vacuum were filled with 6 ml test solution and placed in the dark in a temperature controlled environment.

- Renewal of test solution:
no; for each sampling a different vessel with test solution was used

- Identity and concentration of co-solvent:
no co-solvent

OTHER TEST CONDITIONS
- Adjustment of pH:
buffer solution as described above

- Dissolved oxygen:
excluded

Duration:

720.33 h

pH:

4

Temp.:

20

Initial conc. measured:

0.447 - 0.468 mg/L

Duration:

407 h

pH:

4

Temp.:

50

Initial conc. measured:

0.421 - 0.433 mg/L

Duration:

168.5 h

pH:

4

Temp.:

60

Initial conc. measured:

0.459 - 0.495 mg/L

Duration:

720 h

pH:

7

Temp.:

20

Initial conc. measured:

0.468 - 0.492 mg/L

Duration:

291.5 h

pH:

7

Temp.:

50

Initial conc. measured:

0.456 - 0.473 mg/L

Duration:

167.5 h

pH:

7

Temp.:

60

Initial conc. measured:

0.474 - 0.524 mg/L

Duration:

720 h

pH:

9

Temp.:

20

Initial conc. measured:

0.509 - 0.588 mg/L

Duration:

336 h

pH:

9

Temp.:

50

Initial conc. measured:

0.47 - 0.522

Duration:

166.5 h

pH:

9

Temp.:

60

Initial conc. measured:

0.465 - 0.539

Number of replicates:

2 replicates for each sampling time

Positive controls:

no

Negative controls:

yes

Remarks:

Blank buffer solutions were diluted in a 1:1 (v:v) ratio with isopropanol formate buffer mix and analysed at t=0.

Statistical methods:

Response (R) Peak area of the test substance [units]
Calibration curve: R = a x Cn + b
where: Cn = nominal concentration [µg/l]
a = slope [units × l/µg]
b = intercept [units]
Analysed concentration (Ca = (R-b)/a x d [µg/l]
where: d = dilution factor

Recovery Ca/Cn x 100%
where: Cn = nominal concentration [µg/l]

Degree of hydrolysis (mean c0 -ct) / mean C0 x 100%
where: C0 = concentration at t=0
Ct = concentration at t=x time

Relative concentration Cr = Ct / meanC0 x 100%
where: C0 = concentration at t=0
Ct = concentration at t=x hours

Pseudo-first order curve 10logCr = -a x t + b
where: t = time [hours]
a = slope [hours-1]
b = intercept

Rate constant kobs = - a x 2.303 [hours-1]
where: 2.303 is the conversion factor between natural and base 10 logarithms

Arrhenius equation lnKobs = -E / (R x T) + ln A
where: A plot of ln kobs versus 1/T gives a linear relationship with a slope of – E/R and intercept ln A

Half-life time (t1/2 = ln2 / kobs [hours]

Transformation products:

not specified

% Recovery:

91

pH:

4

Temp.:

20 °C

Duration:

720 h

% Recovery:

85

pH:

4

Temp.:

50 °C

Duration:

407 h

% Recovery:

95

pH:

4

Temp.:

60 °C

Duration:

168 h

% Recovery:

96

pH:

7

Temp.:

20 °C

Duration:

720 h

% Recovery:

93

pH:

7

Temp.:

50 °C

Duration:

291 h

% Recovery:

99

pH:

7

Temp.:

60 °C

Duration:

167 h

% Recovery:

109

pH:

9

Temp.:

20 °C

Duration:

720 h

% Recovery:

99

pH:

9

Temp.:

50 °C

Duration:

336 h

% Recovery:

100

pH:

9

Temp.:

60 °C

Duration:

166 h

pH:

4

Temp.:

20 °C

Hydrolysis rate constant:

-0 h-1

DT50:

> 30 d

Type:

(pseudo-)first order (= half-life)

Remarks on result:

other: 0.033 = coefficient of correlation low; wrong sign for slope (indicating concentration increase); ">30d" indicating half-life longer than time of measurement

pH:

4

Temp.:

50 °C

Hydrolysis rate constant:

0.006 h-1

DT50:

4.5 d

Type:

(pseudo-)first order (= half-life)

Remarks on result:

other: 0.835 = coefficient of correlation for pseudo-first order curve

pH:

4

Temp.:

60 °C

Hydrolysis rate constant:

0.016 h-1

DT50:

1.8 d

Type:

(pseudo-)first order (= half-life)

Remarks on result:

other: 0.874 = coefficient of correlation for pseudo-first order curve

pH:

7

Temp.:

20 °C

Hydrolysis rate constant:

-0.001 h-1

DT50:

> 30 d

Type:

(pseudo-)first order (= half-life)

Remarks on result:

other: 0.518 = coefficient of correlation low; wrong sign for slope (indicating concentration increase); ">30d" indicating half-life longer than time of measurement

pH:

7

Temp.:

50 °C

Hydrolysis rate constant:

0.009 h-1

DT50:

3.4 d

Type:

(pseudo-)first order (= half-life)

Remarks on result:

other: 0.968 = coefficient of correlation for pseudo-first order curve

pH:

7

Temp.:

60 °C

Hydrolysis rate constant:

0.017 h-1

DT50:

1.7 d

Type:

(pseudo-)first order (= half-life)

Remarks on result:

other: 0.984 = coefficient of correlation for pseudo-first order curve

pH:

9

Temp.:

20 °C

Hydrolysis rate constant:

0 h-1

DT50:

> 30 d

Type:

(pseudo-)first order (= half-life)

Remarks on result:

other: 0.339 = coefficient of correlation low; half-life longer than measured time

pH:

9

Temp.:

50 °C

Hydrolysis rate constant:

0.007 h-1

DT50:

4.2 d

Type:

(pseudo-)first order (= half-life)

Remarks on result:

other: 0.946 = coefficient of correlation for pseudo-first order curve

pH:

9

Temp.:

60 °C

Hydrolysis rate constant:

0.015 h-1

DT50:

1.9 d

Type:

(pseudo-)first order (= half-life)

Remarks on result:

other: 0.942 = coefficient of correlation for pseudo-first order curve

Details on results:

TEST CONDITIONS
- pH measured at beginning and end of each test (compliace: +/- 0.1),
- sterility: filter-sterilised
- temperature:
pH Temperature 1 Temperature 2 Temperature 3
pH 4 19.7°C ± 0.3°C 50.1°C ± 0.3°C 60.1°C ± 0.2°C
pH 7 19.7°C ± 0.3°C 50.0°C ± 0.3°C 60.1°C ± 0.2°C
pH 9 19.7°C ± 0.3°C 50.0°C ± 0.3°C 60.1°C ± 0.2°C
- oxygen: excluded

- Anomalies or problems encountered (if yes):
very low coefficiient of correlation for slope of measurements at 20 °C at pH 4, 7, 9
negative slope for pseudo first order equation (= increase of concentration) for pH 4, 7

TRANSFORMATION PRODUCTS:
not determined, ester hydrolysis expected

VOLATILIZATION (at end of study)
not expected due to ionic substance with high molecular weight with tested very loq vapour pressure

PATHWAYS OF HYDROLYSIS
not described

Preliminary test - Tier 1

A degree of hydrolysis of ≥ 10% was observed at pH 4, pH 7 and pH 9 after 5 days at 50.1°C ± 0.1°C. According to the guideline, the higher Tier test was required to determine the half-life time of the test substance.

A small response at the retention time of the test substance was detected in the chromatograms of the blank buffer solutions. The response was comparable to the response in the analytical blanks.

The mean recoveries of the of the test substance containing buffer pH 4 solutions at t=0 fell within the criterion range of 90-110%. The mean recoveries of the test substance containing buffer pH 7 and pH 9 solutions at t=0 was 125% and 132%, which might be caused by matrix effect. To exclude this matrix effect during the main study, the calibration solutions will be prepared using the buffer solutions instead of water.

Main study - Tier 2

pH 4

A small response at the retention time of the test substance was detected in the chromatogram of the blank buffer solutions. The responses were comparable to the responses in the analytical blank.

The mean recoveries of the test substance containing buffer solutions at t=0 at pH 4 and 20ºC, and at pH 4 and 60ºC fell within the criterion range of 90-110%. The mean recovery at pH 4 and 50°C was slightly lower with 85%. The mean recoveries of the buffer solutions fell within the acceptable range for nonlabelled chemicals of 70-110%. It demonstrated that the analytical method was adequate to support the hydrolysis study on the test substance.

For testing of pseudo-first order kinetics the mean logarithms of the relative concentrations between 10% and 90% were plotted against time. A linear relationship was observed at temperatures of 20°C and 50°C, whereas the relationship seemed more exponential at 60°C. In order to obtain a value for the hydrolysis half-life times of the test substance, the model for pseudo-first order reactions was applied at all temperatures. The logarithms of the relative concentrations were correlated with time using linear regression analysis.

The rate constant (kobs) and half-life time of the test substance at each temperature was obtained and the Arrhenius equation was used to determine the rate constant and half-life time at 25°C.

pH 7

A small response at the retention time of the test substance was detected in the chromatogram of the blank buffer solutions. The response was comparable to the response in the analytical blank.

The mean recoveries of the test substance containing buffer solutions at t=0 fell within the criterion range of 90-110%. It demonstrated that the analytical method was adequate to support the hydrolysis study on the test substance.

For testing of pseudo-first order kinetics the mean logarithms of the relative concentrations between 10% and 90% were plotted against time. At all temperatures linear relationships were obtained.

The half-life times of the test substance were determined according to the model for pseudo-first order reactions. All logarithms of the relative concentrations were correlated with time using linear regression analysis.

The rate constant (kobs) and half-life time of the test substance at each temperature was obtained and the Arrhenius equation was used to determine the rate constant and half-life time at 25°C.

pH 9

A small response at the retention time of the test substance was detected in the chromatogram of the blank buffer solutions. The response was comparable to the response in the analytical blank.

The mean recoveries of the test substance containing buffer solutions at t=0 fell within the criterion range of 90-110%. It demonstrated that the analytical method was adequate to support the hydrolysis study on the test substance.

For testing of pseudo-first order kinetics the mean logarithms of the relative concentrations between 10% and 90% were plotted against time. A linear relationship was observed at temperatures of 20°C and 50°C, whereas the relationship seemed more exponential at 60°C. In order to obtain a value for the hydrolysis half-life times of the test substance, the model for pseudo-first order reactions was applied at all temperatures. The logarithms of the relative concentrations were correlated with time using linear regression analysis.

The rate constant (kobs) and half-life time of the test substance at each temperature was obtained and the Arrhenius equation was used to determine the rate constant and half-life time at 25°C.

Validity criteria fulfilled:

yes

Conclusions:

The half-life of MDIPA-Esterquat C16-18 and C18 unsatd. at 20 (measured/extrapolated), 25 (extrapolated), 50 (measured) and 60 (measured) °C was determined to be
for pH4: >30 / 64.5, 41.3, 4.5, 1.8 days
for pH7: >30 / 28.5, 10.1, 3.4, 1.7 days
for pH9: 84/46.5, 31.2, 4.2, 1.9 days

Executive summary:

The hydrolysis of MDIPA-Esterquat C16-18 and C18 unsatd. was tested according to OECD Guideline 111. Hydrolysis was examined by measurement of the concentration decrease of the test substance by HPLC-MS with mass-spectroscopic determination of the mixed C16/C18 esterquat cation.

For pH 4 and 20, 50 and 60 °C the half-life is reported to be > 30, 4.5, 1.8 days (calculated directly from measurement at the corresponding temperature).

For pH 7 and 20, 50 and 60 °C the half-life is reported to be > 30, 3.4, 1.7 days (calculated directly from measurement at the corresponding temperature).

For pH 9 and 20, 50 and 60 °C the half-life is reported to be 84, 4.2, 1.9 days (calculated directly from measurement at the corresponding temperature).

For 20 °C but not for 50 and 60 ° measurements have a high statistical variance. The calculated rate constants resp. the slopes for the pseudo-first order curve correlate well with measurements for 50 and 60 °C but not for 20 °C:

coefficients of correlation for 20 °C for pH 4, 7, 9 are 0.0330, 0.518, 0.339 whereas for 50 and 60 ° these coefficients of correlation are in the range of 0.835 to 0.984.

For measurements at 20 °C pH 4 and 7, the calculated rate constants suggests an increase of test substance.

To bypass statistically questionable numbers for the half-life from measurements at 20 °C, the Arrhenius equation is used to calculate these numbers from measurements at 50 and 60 °C:

pH 4, 20 and 25 °C, half-lifes 64.5 and 41.3 days

pH 7, 20 and 25 °C, half-lifes 28.5 and 20.1 days

pH 9, 20 and 25 °C, half-lifes 46.5 and 31.2 days.

Description of key information

The half-life of MDIPA-Esterquat C16-18 and C18 unsatd. at 20 (measured/extrapolated), 25 (extrapolated), 50 (measured) and 60 (measured) °C was determined to be

for pH4: >30 / 64.5, 41.3, 4.5, 1.8 days

for pH7: >30 / 28.5, 10.1, 3.4, 1.7 days

for pH9: 84/46.5, 31.2, 4.2, 1.9 days

Key value for chemical safety assessment

Half-life for hydrolysis:

28.5 d

at the temperature of:

20 °C

Additional information

The hydrolysis of MDIPA-Esterquat C16-18 and C18 unsatd. was tested according to OECD Guideline 111. Hydrolysis was examined by measurement of the concentration decrease of the test substance by HPLC-MS with mass-spectroscopic determination of the mixed C16/C18 esterquat cation.

For pH 4 and 20, 50 and 60 °C the half-life is reported to be > 30, 4.5, 1.8 days (calculated directly from measurement at the corresponding temperature).

For pH 7 and 20, 50 and 60 °C the half-life is reported to be > 30, 3.4, 1.7 days (calculated directly from measurement at the corresponding temperature).

For pH 9 and 20, 50 and 60 °C the half-life is reported to be 84, 4.2, 1.9 days (calculated directly from measurement at the corresponding temperature).

For 20 °C but not for 50 and 60 °, the measurements have a high statistical variance. The calculated rate constants resp. the slopes for the pseudo-first order curve correlate well with measurements for 50 and 60 °C but not for 20 °C: coefficients of correlation for 20 °C for pH 4, 7, 9 are 0.0330, 0.518, 0.339 whereas for 50 and 60 ° these coefficients of correlation are in the range of 0.835 to 0.984.

For measurements at 20 °C pH 4 and 7, the calculated rate constants suggests an increase of test substance. To bypass statistically questionable numbers for the half-life from measurements at 20 °C, the Arrhenius equation is used to calculate these numbers from measurements at 50 and 60 °C:

pH 4, 20 and 25 °C, half-lifes 64.5 and 41.3 days

pH 7, 20 and 25 °C, half-lifes 28.5 and 20.1 days

pH 9, 20 and 25 °C, half-lifes 46.5 and 31.2 days.