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Hydrolysis

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Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Qualifier:
no guideline followed
Principles of method if other than guideline:
This study was designed specifically to provide confirmation of the hydrolysis behaviour and identity of the hydrolysis products of Mergal® V615 under conditions representative of those of the biocidal product in use.
GLP compliance:
no
Remarks:
Special study for confirmatory purpose. Therefore, not performed under GLP but with detailed documentation.
Analytical monitoring:
yes
Transformation products:
yes
No.:
#1
No.:
#2
Key result
pH:
8.5
Temp.:
25 °C
DT50:
< 2 h
Type:
(pseudo-)first order (= half-life)

Concentrations (%) of the hydrolysis products of Mergal® V615 at 25°C obtained by13C‑NMR, quantified by external calibration

Substance

Time (h)

1.98

4.02

6.05

8.08

24.05

Mean

Ethylene glycol

0.142

0.143

0.145

0.142

0.144

0.143

Formaldehyde

0.141

0.140

0.140

0.142

0.141

0.141

 0.315% preparation of Mergal® V615 mixed in a 0.1 M aqueous borate buffer solution

Half-life was not calculated, but the hydrolysis DT50 and DT100 of Mergal® V615 are < 2 h. Complete release of formaldehyde and ethylene glycol had occurred at the initial analysis (1.98 h) and practically identical concentrations of the hydrolysis products were observed at all four subsequent measurements (4.02, 6.05, 8.08 and 24.05 h).

Under conditions representative of the uses of Mergal® V615 in PT06 and PT13 applications, the test substance was rapidly and completely hydrolysed. The hydrolysis products consisted of free formaldehyde and ethylene glycol only. 

Validity criteria fulfilled:
yes
Executive summary:

A non-guideline study of the hydrolysis of Mergal® V615 was conducted in an aqueous borate buffer system at a pH (8.5) and concentration (0.315%) both relevant to the use of the test substance as a preservative of in-can articles (PT06) and metal-working fluids (PT13). Hydrolysis products were identified and quantified by means of 13C NMR analysis, a non-destructive technique necessary to avoid the analysis itself influencing the hydrolysis.

Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
2000
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
test procedure in accordance with generally accepted scientific standards and described in sufficient detail
Qualifier:
according to
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)
Deviations:
no
GLP compliance:
yes
Analytical monitoring:
yes
Buffers:
Buffered test solutions were kept at 50 ± 0.5°C in a water bath. Aliquots of each test solution were analysed before incubation, after 2.4 hours and after 120 hours.
Test performance:
. Concentration was approximately 5 mg/mL at each pH at the start of the study.
Transformation products:
yes
No.:
#1
Details on hydrolysis and appearance of transformation product(s):
The test item is a reaction product between formaldehyde and ethylene glycol in the presence of water following the general formula:
CH2O + 2ROH ⇄ CH2(OR)2 + H2O
Addition of water shifts the equilibrium to the left and free formaldehyde is formed in a rapid reaction.
Key result
pH:
4
Temp.:
50 °C
DT50:
< 2.4 h
Type:
(pseudo-)first order (= half-life)
Key result
pH:
7
Temp.:
50 °C
DT50:
< 2.4 h
Type:
(pseudo-)first order (= half-life)
Key result
pH:
9
Temp.:
50 °C
DT50:
< 2.4 h
Type:
(pseudo-)first order (= half-life)

Hydrolysis of MERGAL® V615 at 50°C

pH

Nominal concentration

[μg / 10 mL]

Measured concentration   [μg / 10 mL]

T = 0

(Before incubation)

T = 2.4 hours

T = 5 days

4.0

33.34

28.82

29.67

27.37

27.48

31.56

31.77

7.0

36.47

33.28

31.26

29.98

29.81

35.23

35.13

9.0

35.30

30.15

30.17

28.79

29.02

32.55

34.99

 

Dt values were not calculated. Plots of concentration versus time were not provided.

Validity criteria fulfilled:
no
Conclusions:
According to EEC Directive 92/69, Section C.7, the estimated half-life time is shorter than one day under representative environmental conditions (25°C). Therefore, ‘MERGAL V615’ was considered to be hydrolytically not stable, and no further testing was necessary.
Executive summary:

A GLP-compliant study of the hydrolysis of ‘MERGAL V615’ was conducted according to OECD No. 111 and EEC Directive 92/69, C.7, without deviation. Dilutions of test material in oxygen-free buffer solutions were incubated at pH 4, 7, and 9 at 50 °C for five days. Samples were taken for analysis at initiation (before incubation), 2.4 hours, and 120 hours, i.e., five days. Test substance content was determined by spectrophotometric analysis following derivatization. 

The active substance in MERGAL® V615 is unstable to hydrolysis at pH 4, 7, and 9. At the initial analysis, almost all, i.e., 87 %, of the potential formaldehyde yield had already been released. After 2.4 hours the yield of free formaldehyde was more than 50%. 

Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
2002-2007
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
comparable to guideline study
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Deviations:
not applicable
GLP compliance:
no
Remarks:
the studies follow quality assurance standards
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
Samples stored at 4 or 7 °C before analysis
Details on test conditions:
TEST SYSTEM
Different solutions of the test substances were filled into 5 mm NMR tubes.
Study 1: 1% solution in H2O/DMSO-D6 (90/10), 20°C, pH 6.5 and 7.2, no buffer solution
Study 2: (Ethylendioxy)dimethanol / D2O: 100/0, 50/50 and 20/80, no buffer solution
Study 3: 1% solution in H2O/DMSO-D6 (90/10), 20°C, pH 2, 4, 5.4, 7.1 and 8.9 in aqueous or aqueous buffer solution (pH 2 = 10mM HCl, pH 4 = 30mM acetate buffer, pH 5.4 = water, pH 7.1 = 25mM phosphate buffer, pH 8.9 = 50mM borate buffer)
- Test system:
5 mm NMR tubes
Study 1: two series of measurement;
Study 3: capillary insert for acetone-d6
- Temperature: Study 1: 20°C; Study 2: no data; Study 3: 20°C
- pH: Study 1: 6.5 and 7.2 ; Study 2: no data; Study 3: 2, 4, 5.4, 7.1 and 8.9
Duration:
14 h
pH:
6.5
Temp.:
20 °C
Initial conc. measured:
1 other: %
Remarks:
Study 1
Duration:
14 h
pH:
7.2
Temp.:
20 °C
Initial conc. measured:
1 other: %
Remarks:
Study 1
Number of replicates:
1
Transformation products:
yes
No.:
#1
Key result
pH:
2
Temp.:
20 °C
DT50:
0.48 h
Type:
(pseudo-)first order (= half-life)
Key result
pH:
4
Temp.:
20 °C
DT50:
0.91 h
Type:
(pseudo-)first order (= half-life)
Key result
pH:
5.4
Temp.:
20 °C
DT50:
0.33 h
Type:
(pseudo-)first order (= half-life)
Key result
pH:
7.1
Temp.:
20 °C
DT50:
0.1 h
Type:
(pseudo-)first order (= half-life)
Key result
pH:
8.9
Temp.:
20 °C
DT50:
0.08 h
Type:
(pseudo-)first order (= half-life)
Details on results:
The formation of the hydrolysis product formaldehyde is determined. The results prove this formation not to be a (pseudo) first-order reaction due to subsequent reaction(s). Therefore, no calculated half-life can be presented. However, the half-life of hydrolysis is < 1 hours for a 1% solution as the rise of concentration of formaldehyde within ca. 1 hour is up to minimum 24 to 26% (equally to > 50% of totally releasable formaldehyde).

Concentration and hydrolysis values

Study 1:

 pH 6.5

Time [h]

Formaldehyde [%]

0.38

13.36

0.88

24.85

2.44

40.36

3.99

41.83

5.55

45.60

7.10

46.72

8.65

47.54

10.21

47.93

11.76

47.45

13.31

47.08

 

pH 7.2

Time [h]

Formaldehyde [%]

0.45

15.84

0.97

26.19

2.53

38.94

4.10

41.83

5.67

46.31

8.27

45.93

9.83

46.86

11.40

44.95

12.97

47.64

At both pH values, the percentage of formaldehyde reached a plateau after 5-6 hours.

 

Study 2:

 amounts of transformation products are determined in dependent of the concentration

 

Study 3:

pH 2

Time [h]

H2CO (%)#

0.25

22.75

0.53

32.81

1.12

41.46

1.9

43.23

2.68

43.93

3.87

46.01

5.43

46.01

8.07

46.26

 

pH 4

Time [h]

H2CO (%)#

0.28

9.71

0.57

19.16

1.15

30.03

1.93

36.7

2.72

40.24

3.5

41.96

4.28

43.02

5.57

44.49

6.8

45.55

8.45

46.01

 

pH 5

Time [h]

H2CO (%)

0.27

18.5

0.55

33.52

1.15

41.91

1.93

45.5

2.72

40.24

3.5

41.96

 

pH 7

Time [h]

H2CO (%)#

0.23

35.89

0.33

41.81

0.53

44.59

1.18

45.9

1.97

45.75

2.75

46.01

# In the previous study 1 the apparent release of formaldehyde started later which was due to a less sensitive NMR probe head

 

pH 9

Time [h]

H2CO (%)

0.27

41.2

0.57

45.85

1.17

46.21

1.95

46.01

2.73

46.21

 

Specification of the transformation products:

 Amount of identified components contained in EGForm and in EGForm/D2O mixtures (study 2):

Component1)

Content (%)

EGForm/D2O

100/0

50/50

20/80

HO-CH2-CH2-OH
Ethylene glycol

5.6

9.7

18.9

HO-CH2-O-CH2-CH2-OH
Monomethylol-ethylene glycol

20.4

24.5

25.1

HO-CH2-O-CH2-O-CH2-CH2-OHb)
asym. Dimethylol-ethylene glycol

10.4

8.6

4.3

HO-CH2-O-CH2-CH2-O-CH2-OH
symmetr. Dimethylol-ethylene glycol

15.0

13.1

7.1

HO-CH2-O-CH2-O-CH2-CH2-O-CH2-OH
Trimethylol-ethylene glycol

14.2

8.7

2.9

H2C(OH)2
Formaldehyde-hydrate2)

0.5

10.9

32.3

HO-CH2-O-CH2-OH
dimer Formaldehyde-hydrate2)

0.4

4.8

8.3

HO-CH2-O-CH2-O- CH2-OH
trimer Formaldehyde-Hydrate
2)

0.1

1.3

1.4

Sum of identified components

66.6

76.2

86.0

1) compounds in italics are provisional structure proposals
2) for summing up, formaldehyde contents calculated from the hydrates were used

Validity criteria fulfilled:
yes
Conclusions:
The studies clearly prove rapid hydrolysis and pH dependency thereof for EGForm. At pH values >7 the most rapid hydrolysis was observed. Products of hydrolysis are formaldehyde and ethyleneglycol. Complete hydrolysis is to be expected under environmental conditions and in human body fluids.
Executive summary:

The hydrolysis of EGForm was studied using 1H and 13C-NMR technique. The test substance was mixed with D2O to obtain a 1% solution at 20°C; pH values were adjusted to either 6.5 or 7.2 in study 1 and in a subsequent study (study 3) to pH 2, 4, 5.4, 7.1 and 8.9. The degree of hydrolysis was measured by detection of free formaldehyde via the 13C-NMR-spectra. In a further study, the individual constituents in EGForm were determined at different dilutions with D2O by applying the same technique.The individual constituents were identified via their characteristical chemical shifts, and quantified via the corresponding intensities.

In the first study, increasing amounts of formaldehyde were observedduring a reaction time of 14 hours, At both pH values, the amount of formaldehyde reached a plateau after 5-6 hours. Equilibrium between the reactants was observed: about 45-50% of formaldehyde content could be determined with respect to the initial weight of EGForm that is nearly the totally releasable formaldehyde (46.8%). Although, exact half-life times can not be calculated as the reaction is no pseudo first order, T1/2-values were estimated from the released formaldehyde in study 3. A clear effect of pH upon the estimated T1/2‑values was demonstrated. Thus T1/2-values were highest at pH 4 and most rapid hydrolysis was demonstrated at pH values >7. However, estimated values indicate a relatively fast hydrolysis (DT50< 1 hour) over the total pH range. The quantification of individual constituents of EGForm (study 2) showed increasing contents of the hydrolysis products ethylene glycol and formaldehyde in parallel to increasing the D2O content. Simultaneously, the content of methylolated ethylene glycols decreased.

Description of key information

Hydrolysis of the test substance was studied using 13C-NMR techniques and spectrophotometric analysis. The degree of hydrolysis was measured by detection of formaldehyde. During the reaction time, increasing amounts of formaldehyde were observed. At all pH values, the content of formaldehyde reached a plateau, an equilibrium between the reactants was observed.

The studies demonstrate the rapid hydrolysis. At large dilutions which are expected under environmental conditions (in wastewaters or surface waters) as well as in human body fluids, the test substance is expected to hydrolyse completely to formaldehyde and ethylene glycol.

Key value for chemical safety assessment

Additional information