Miristalkonium chloride

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

read-across from supporting substance (structural analogue or surrogate)

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 section 13 for details on the read-across justification. The study with the read across substance is considered sufficient to fulfil the information requirements as further explained in the provided endpoint summary.

Reason / purpose for cross-reference:

read-across source

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.

Validity criteria fulfilled:

not specified

Conclusions:

Based on the results of the read across study, the test substance was considered to be hydrolytically stable.

Executive summary:

A study was conducted to determine the hydrolysis of the read across substance, C12-16 ADBAC, according to US EPA Guideline Subdivision N 161-1, in compliance with GLP. The hydrolysis as a function of pH at 25°C was investigated. Hydrolysis rate constants and the half-lives for degradation of the test substance were determined in aqueous buffered solutions of pH 5, 7 and 9 at 25±1°C. Two pH 7 buffers were employed during the study to evaluate buffer catalysis of the degradation process. All experiments were conducted for a 30 d period at a nominal test concentration of 10 µg/mL. The measured pH values in the four buffer systems indicate that they were properly prepared and stable for the duration of the study. The results show that no significant degradation of the test substance occurred over the pH range of 5 to 9 at 25°C. The mean total recovery was 96.3%. Further, an accurate estimate of half-life for the hydrolysis could not be determined since no significant degradation of the test substance was detected during the 30 day evaluation period. Under study conditions, the test substance was considered 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 d study period (Carpenter, 1988). Based on the results of the read across study, the test substance, C14 ADBAC, was considered to be hydrolytically stable.

Description of key information

Based on the results of the read across study, the test substance, C14 ADBAC, can also be considered to be hydrolytically stable.

Additional information

A study was conducted to determine the hydrolysis of the read across substance, C12-16 ADBAC, according to US EPA Guideline Subdivision N 161-1, in compliance with GLP. The hydrolysis as a function of pH at 25°C was investigated. Hydrolysis rate constants and the half-lives for degradation of the test substance were determined in aqueous buffered solutions of pH 5, 7 and 9 at 25±1°C. Two pH 7 buffers were employed during the study to evaluate buffer catalysis of the degradation process. All experiments were conducted for a 30 d period at a nominal test concentration of 10 µg/mL. The measured pH values in the four buffer systems indicate that they were properly prepared and stable for the duration of the study. The results show that no significant degradation of the test substance occurred over the pH range of 5 to 9 at 25°C. The mean total recovery was 96.3%. Further, an accurate estimate of half-life for the hydrolysis could not be determined since no significant degradation of the test substance was detected during the 30 day evaluation period. Under study conditions, the test substance was considered 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 d study period (Carpenter, 1988). Based on the results of the read across study, the test substance, C14 ADBAC, can also be considered to be hydrolytically stable.