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Hydrolysis

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Endpoint:
hydrolysis
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Study period:
From 13 July, 1987 to 12 August, 1987
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Justification for type of information:
Refer to the Quaternary ammonium salts (QAS) category or section 13 of IUCLID for details on the category justification.
Qualifier:
according to guideline
Guideline:
EPA Guideline Subdivision N 161-1 (Hydrolysis)
Deviations:
no
GLP compliance:
yes
Remarks:
US EPA GLP
Radiolabelling:
yes
Analytical monitoring:
yes
Buffers:
Preparation of buffer solutions for the definitive study:
- The pH 5 buffer was prepared by adding 14.8 mL of 0.2 M acetic acid (11.55 mL of acetic acid to 1000 mL of water) to 35.2 mL of 0.2 M sodium acetate (16.4 g of sodium acetate in 1000 mL water). The solution was diluted to 200 mL with water.
- The pH 7 (TRIS) buffer was prepared by adding 378 mL of 0.2 M HCl (16.7 mL of HCl to 983.3 mL of water) to 375 mL of 0.2 M tris (hydroxymethyl) aminomethane (24.2 g of tris in 1000 mL water). The solution was diluted to 1500 mL with water.
- The pH 7 (HEPES) buffer was prepared by diluting 50 mL of 0.01 M N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic cid (HEPES) (2.383 g of HEPES in 1000 mL of water) to a volume of 200 mL and then adding 0.2 M KOH (12.9 g in 1000 mL water) until a pH of 7 was reached.
- The pH 9 buffer was prepared by adding 50 mL of a 0.2 M boric acid (12.4 g of boric acid in 1000 mL of water) to 59 mL of a 0.2 M borax solution (76.3 g borax in 1000 mL water). The solution was diluted to 200 mL with water.

All water used to prepare buffers was Millipore Milli-Q purified, filtered through a 0.2 µm filter and sterilized in autoclave. The pH of each buffer was measured with a Corning Model 140 pH meter. The buffers were then sterilized for 1 h at 250 degF (120 degC) 15 psi.
Details on test conditions:
- Preliminary study:
Determination of an approximate degradation rate; setting of the definitive study sample schedule; evaluation of the adsorption of test containers and of the stability of samples under the storage conditions scheduled during the study. All quantitative radiotracer data for the preliminary study was obtained by radio-thin layer chromatography plate scanner.
- Main study:
1. Preparation of the solution:
The test samples were prepared by placing 1.86 mL of the primary stock (698 ug/mL in deionised water) into each of four Erlenmeyer flasks along with 130 mL of the appropriate buffer. A 1 mL aliquot of acetonitrile was added to each flask to inhibit glass adsorption and promote dissolution of the test compound. 10 mL of the resulting solutions were places in silanized amber vials. Duplicate vials of each solution for each sample point were prepared (48 samples total), and places in a box in a Norlake environmental chamber set at 25±1°C. Samples were prepared at pH 5, 7 (HEPES), 7 (tris) and 9.
2. Treatment of the samples:
- The samples were assayed at Day 0, 1, 3, 7, 14, 22 and 30 for total 14C-activity.
- Duplicate 100 µL aliquots from each vial were analysed by LSC. 100 uL aliquots were spotted on silica gel TLC plates. The TLC plates were then analyzed. The pH was measured with Universal pH indicator papers. The D30 sample's pH was measured also with a Corning pH meter 140.
- In the samples that showed <90% mass accountability, the containers were rinsed with 5 mL of methanol. Duplicate 100 uL aliquots from each vial were analyzed by LSC.
- The concentration of the test substance in the samples was determined by multiplying the total 14C-activity found into the sample, expressed as the test substance equivalents in ug/g, by the fraction that was determined to be the test substance by TLC. The concentration found at each time point was divided by that found at time zero to give percent of time zero.
- The degradation rate of the test substance was calculated assuming first order kinetics. The natural logarithm of the percent of time zero concentration was plotted versus timer and linear regression analysis of equation 1 was used to determine the slope of the line, which is k, the rate constant. The half-life was then calculated by equation 2.
First order kinetics calculations for the hydrolysis of the test substance:
Equation 1: y = mx+b
Where: y = dependent variable
x = independent variable
b = a constant
m= slope of the line
Equation 2: t1/2 = ln2/k
where: t1/2 = half life of the test compound
K= reaction rate constant
Duration:
30 d
Temp.:
25 °C
Initial conc. measured:
10 µg/L
Number of replicates:
Two
Preliminary study:
The preliminary study conducted with buffered solutions of the test substance indicated that the test substance was stable and a 30-d hydrolysis period would be appropriate to evaluate its hydrolysis rate.
- The test substance was found to adsorb onto the glass. Therefore the glass for the definitive study was silanized. Acetonitrile (1%) was used as a co-solvent to reduce the adsorption to the glass-ware.
- It was also determined that samples were stable when stored in either the refrigerator or the freezer.
Transformation products:
no
Details on hydrolysis and appearance of transformation product(s):
- The measured pH values in the four buffer systems indicate that the systems were properly prepared and were stable for the duration of the study. The observed pH for the test substance hydrolysis samples during the 30-d study period ranged from 5 to 5.01, 7 to 7.02, 6.96 to 7 and 9 to 9.02 for pH 5, 7(H), 7(t) and 9 respectively.
- The data for the hydrolysis evaluations in the four buffer systems demonstrate that no significant degradation of the test substance occurred over the pH range of 5 to 9 at 25°C. The mass balance of respective pH hydrolysis samples are presented below under 'total recovery of the test substance'. The overall mean 14C-activity accountability for this study was 96.3%.

% Recovery:
94.6
St. dev.:
4.65
pH:
5
Temp.:
25 °C
Duration:
30 d
% Recovery:
96.8
St. dev.:
3.47
pH:
7
Temp.:
25 °C
Duration:
30 d
% Recovery:
94.4
St. dev.:
4.88
pH:
7
Temp.:
25 °C
Duration:
30 d
% Recovery:
99.5
St. dev.:
3.49
pH:
9
Temp.:
25 °C
Duration:
30 d
Key result
Remarks on result:
other: no significant degradation of the test substance was detected during the 30-d evaluation period
Other kinetic parameters:
- An accurate estimated of half-life for the hydrolysis could not be determined since no significant degradation of the test substance was detected during the 30-d evaluation period.

For result tables and figures, kindly refer to the attached background material section of the IUCLID.

Validity criteria fulfilled:
not specified
Conclusions:
Under the conditions of the study, the read across substance was determined to be hydrolytically stable in the pH range of 5 to 9 at 25°C with a very small amount of degradation during the 30-day study period.
Executive summary:

A study was conducted to determine the hydrolysis of the read across substance, C12-16 ADBAC (30% active in water, radiochemical purity: 98.4%) in aqueous buffered solutions of pH 5, 7 and 9 at , according to US EPA Guideline Subdivision N 161-1, in compliance with GLP. Two pH 7 buffers were employed during the study to evaluate buffer catalysis of the degradation process. The hydrolysis rate constants and the half-lives for degradation were determined as a function of pH at 25°C. All experiments were conducted for a 30-day period at a nominal test concentration of 10 µg/mL. Quantification of the read across substance and characterization of hydrolysis products were done by thin layer chromatography. Based on the data generated during the study, the read across substance was found to be hydrolytically stable in the pH range 5-9. An accurate estimate of half-life for the hydrolysis could not be determined since no significant degradation of the read across substance was detected during the 30-day evaluation period. The overall mean 14C-activity based on total recovery was determined to be 96.3%. Under the conditions of the study, the read across substance was determined to be hydrolytically stable in the pH range of 5 to 9 at 25°C with only a very small amount of degradation during the 30-day study period (Carpenter, 1988). Based on the results of the read across, a similar result is expected for the test substance.

Endpoint:
hydrolysis
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Study period:
From 07 June, 1996 to 19 July, 1996
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Justification for type of information:
Refer to the Quaternary ammonium salts (QAS) category or section 13 of IUCLID for details on the category justification.
Qualifier:
according to guideline
Guideline:
EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)
Version / remarks:
Cited as Directive 84/449/EEC, C.10
GLP compliance:
yes (incl. QA statement)
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
At each sampling time 750 µL of sample was taken and added to 750 µL mobile phase. The samples were stored in the freezer until analyses. The temperature of the thermostatic water bath was checked at least at the start and end of the tests and at each sampling time.
Buffers:
pH=4: 100 mL of 0.5 M potassium hydrogen phtalate and 0.8 mL 0.5 M NaOH made up to 1 L with deionized water
pH=7: 100 mL of 0.5 M potassium hydrogen phosphate and 5.92 mL 5 M NaOH made up to 1 L with deionized water
pH=9: 100 mL of 0.5 M boric acid, 100 mL of 0.5 M potassium chloride and 100 mL 4.32 M NaOH made up to 1 L with deionized water
Details on test conditions:
Glassware: Air-tight glass vessels
Other equipment: Thermostatic water bath, thermometer, pH meter.
Method of sterilization: All glassware and buffers were sterilized by autoclaving.
Duration:
8 350 min
pH:
4
Temp.:
20 °C
Initial conc. measured:
ca. 4.606 mg/L
Duration:
8 350 min
pH:
7
Temp.:
20 °C
Initial conc. measured:
ca. 5.455 mg/L
Duration:
8 350 min
pH:
9
Temp.:
20 °C
Initial conc. measured:
ca. 2.948 mg/L
Number of replicates:
2
Transformation products:
not specified
Key result
pH:
4
Temp.:
20 °C
DT50:
>= 1 yr
Key result
pH:
7
Temp.:
20 °C
DT50:
>= 1 yr
Key result
pH:
9
Temp.:
20 °C
DT50:
>= 1 yr
Details on results:
- After 5 days at 50°C, less than 10% decrease in the test substance concentration was measured at all three pH values. It was therefore concluded that test substance was hydrolytically stable with a half-life equal to or greater than one year at pH 4, 7 and 9 at ambient temperatures. A minor decrease of test substance at all three tested pH values was observed, which was probably due to inaccuracies of the test method and/or the analytical method.
- The results of this study with C12-16 chains of the test substance were representative for the whole range of products. All substances have the same molecular structure, similar very high solubility and are completely discosiated in water (in cationic form). All products are only on the market as solutions in water, and are known to be stable for many years.

For result tables, kindly refer to the attached background material section of the IUCLID.

Validity criteria fulfilled:
not specified
Remarks:
Prelimnary study
Conclusions:
Under the study conditions, the read across substance was hydrolytically stable with a half-life equal to or greater than one year at pH 4, 7 and 9 at ambient temperature.
Executive summary:

A study was performed to determine the hydrolysis of the read across substance, C12-16 ADBAC (50.2% active in water) according to EU Method C.7, in compliance with GLP. The hydrolytic stability was investigated in buffer solutions of pH 4, 7 and 9 in a water bath at 50ºC for 5 days. Samples were taken at t0 and at regular intervals afterwards to determine half-life time (t½). According to the guideline, if t½ is less than 2.4 h, or if less than 10% of the read across substance is hydrolysed in 5 d, no further tests need to be performed at that pH. Under the conditions of the study after 5 days at 50°C, less than 10% decrease in read across substance concentration was measured at all three pH values. Therefore, the read across substance was concluded to be hydrolytically stable with a half-life equal to or greater than one year at pH 4, 7 and 9 at ambient temperature (Geurts, 1996). Based on the results of the read across, a similar result is expected for the test substance.

Description of key information

Based on the results of the read across studies and in line with the biocides assessment report, the test substance is considered to be hydrolytically stable with half-life equal to or greater than one year at pH 4, 7 and 9 at ambient temperature.

Key value for chemical safety assessment

Half-life for hydrolysis:
1 yr
at the temperature of:
25 °C

Additional information

Study 1. A study was performed to determine the hydrolysis of the read across substance, C12-16 ADBAC (50.2% active in water) according to EU Method C.7, in compliance with GLP. The hydrolytic stability was investigated in buffer solutions of pH 4, 7 and 9 in a water bath at 50ºC for 5 days. Samples were taken at t0 and at regular intervals afterwards to determine half-life time (t½). According to the guideline, if t½ is less than 2.4 h, or if less than 10% of the read across substance is hydrolysed in 5 d, no further tests need to be performed at that pH. Under the conditions of the study after 5 days at 50°C, less than 10% decrease in read across substance concentration was measured at all three pH values. Therefore, the read across substance was concluded to be hydrolytically stable with a half-life equal to or greater than one year at pH 4, 7 and 9 at ambient temperature (Geurts, 1996).

Study 2. A study was conducted to determine the hydrolysis of the read across substance, C12-16 ADBAC (30% active in water, radiochemical purity: 98.4%) in aqueous buffered solutions of pH 5, 7 and 9 at 25ºC, according to US EPA Guideline Subdivision N 161-1, in compliance with GLP. Two pH 7 buffers were employed during the study to evaluate buffer catalysis of the degradation process. The hydrolysis rate constants and the half-lives for degradation were determined as a function of pH at 25°C. All experiments were conducted for a 30-day period at a nominal test concentration of 10 µg/mL. Quantification of the read across substance and characterization of hydrolysis products were done by thin layer chromatography. Based on the data generated during the study, the read across substance was found to be hydrolytically stable in the pH range 5-9. An accurate estimate of half-life for the hydrolysis could not be determined since no significant degradation of the read across substance was detected during the 30-day evaluation period. The overall mean 14C-activity based on total recovery was determined to be 96.3%. Under the conditions of the study, the read across substance was determined to be hydrolytically stable in the pH range of 5 to 9 at 25°C with only a very small amount of degradation during the 30-day study period (Carpenter, 1988).

Further, the biocides assessment report available on the read across substance also concluded that “Alkyl (C12-16) dimethylbenzyl ammonium chloride was hydrolytically stable during the 30-day hydrolysis study at pH 5, 7 or 9 at 25°C” (ECHA biocides assessment report, 2015). 

Based on the results of the read across studies and in line with the biocides assessment report, the test substance is considered to be hydrolytically stable with half-life equal to or greater than one year at pH 4, 7 and 9 at ambient temperature.