Zinc bis(hydroxymethanesulphinate)

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

February 2010 - April 2010

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: GLP-guideline study: The test was made in accordance with the „Revised OECD Principles of Good Laboratory Practice“ (Paris, 1997) as stated in the following guideline: OECD 111

Qualifier:

according to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Deviations:

not specified

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):
Physico-chemical properties
- Vapour pressure: 2.68 * 10-5 hPa at 20 °C
- Water solubility > 1,000 g/L
- log Pow < -3
- pKa1 6.6; pKa2 9.6;
- Base or acid catalysis of test material:
- UV absorption:
- Stability of test material at room temperature: stable at room temperature

OTHER PROPERTIES (if relevant for this endpoint)

Radiolabelling:

no

Details on sampling:

Measurement of Samples:
1 ml sample solution was diluted with 100 ml of demineralised water. After addition of 2 ml formaldehyde solution 30 % and 2 drops phenolphthalein, the solution was adjusted to pH 3 with 0.05-m sulphuric acid. Then 2 ml starch solution were added and the test solution was titrated with I2 0.005-m (f = 0.9718) to blue colour. Every sample solution was titrated in duplicate.

Buffers:

General: Deionised water was used for the solution of the test item and for the preparation of the buffer solutions.

Buffer-Solution, pH 4:
CH3COOH, 2M 16.0 mL
CH3COONa, 1M 8 mL
Water ad 200 mL
pH is adjusted to 4.00 using acetic acid.

Buffer-Solution, pH 7:
KH2PO4 1.7418 g
Water 50 mL
NaOH, 2M 2.98 mL
Wate ad 200 mL
pH is adjusted to 7.00 using NaOH 2M.

Buffer-Solution, pH 9:
H3BO3 0.7462 g
KCl 0.6188 g
Water 100 mL
NaOH, 2M 2.15 mL
Water ad 200 mL
pH is adjusted to 9.00 using NaOH 2M.

Estimation method (if used):

-

Details on test conditions:

TEST SYSTEM
- Type, material and volume of test flasks, other equipment used:
Glassware: All test vessels was autoclaved before use. Duran 3.3 was used. Tubes, nominal volume 10 ml, with teflon seals were used as test
flasks.
Incubation Chambers: Incubation chamber #5 Memmert, adjustable to 50  0.5 °C. Usage and calibration follow-ing the corresponding SOP in
the current edition.
Other Instruments and Devices: The following instruments and devices were used for the performance of the study:
• Autoclave Sanyo MLS 3020
• pH-Meter wtw pH 540 GLP
• PT100-thermometer testo 720
• Adjustable pipettes with one-way tips Rainin® LAUS No.: 23, 30, 39
• Burette (maximum volume 10 mL)
• Sterilised nylon syringe filters 0,2 µm
• Standard laboratory glassware

TEST MEDIUM
- Kind and purity of water: deionised water
- Preparation of test medium: A stock solution was prepared by dissolving 300.2 mg test item in deionised water and filling up to volume in a 100 ml volumetric flask. Stock solution of the test item concentration: 3.0 g/L . The concentrations of the test item were measured by titration with iodine solution at the beginning und after storage at 50 °C for five days

Duration:

5 d

pH:

4

Temp.:

50 °C

Initial conc. measured:

1 500 mg/L

Number of replicates:

two per pH and one blank

Positive controls:

not specified

Negative controls:

not specified

Preliminary study:

Tier 1:
Performance: 08. Feb. – 15. Feb. 2010
pH values: 4.0; 7.0; 9.0
Buffers: see under "buffers"
Test temperature: 50 ± 0.5 °C
Number of replicates: two per pH and one blank

Test performance:

see "Preliminary study"

Transformation products:

not measured

Details on hydrolysis and appearance of transformation product(s):

no transformation products measured.

% Recovery:

68

pH:

4

Temp.:

20 °C

Duration:

5 d

% Recovery:

77

pH:

7

Temp.:

20 °C

Duration:

5 d

% Recovery:

66

pH:

9

Temp.:

20 °C

Duration:

5 d

Other kinetic parameters:

none

Details on results:

MAJOR TRANSFORMATION PRODUCTS
At pH5:
- Range of maximum concentrations in % of the applied amount and day(s) of incubation when observed:see table 2
- Range of maximum concentrations in % of the applied amount at end of study period: see table 2

At pH7: see table 1
- Range of maximum concentrations in % of the applied amount and day(s) of incubation when observed: see table 2
- Range of maximum concentrations in % of the applied amount at end of study period: see table 2

At pH9: see table 1
- Range of maximum concentrations in % of the applied amount and day(s) of incubation when observed: see table 2
- Range of maximum concentrations in % of the applied amount at end of study period:see table 2

A solution of the test item in water was mixed with buffer solutions (pH values: 4, 7, and 9), filtered sterile and degassed using sterile Argon. The resulting solutions were stored at 50 °C for aperiod of five days. Sam pies were taken at the beginning and after five days. The analysis of the sampies (titration with lodine) showed significant changes in the concentration

of the test item within five days.

table 1: (Tier 1): The consumptions of the titrations and the calculated concentration of the test item in the sample solutions:

Sample	Volume 1 in mL	Volume 2 in mL	Mean Volume in mL	Conc. in mg/L
Blank pH 4 day 0	0.3	0.25	0.275	-
Blank pH 7 day 0	0.3	0.3	0.3
Blank pH 9 day 0	0.3	0.3	0.3
09111902G pH 4 day 0	4.5	4.5	4.5	1500
09111902G pH 7 day 0	4.5	4.5	4.5	1500
09111902G pH 9 day 0	4.5	4.5	4.5	1500
Blank pH 4 day 5	0.3	0.3	0.3	-
Blank pH 7 day 5	0.3	0.3	0.3
Blank pH 9 day 5	0.3	0.3	0.3
09111902G pH 4 day 5 a	3.1	3.1	3.1	1020
09111902G pH 4 day 5 b	3.1	3.1
09111902G pH 7 day 5 a	3.4	3.4	3.475	1150
09111902G pH 7 day 5 b	3.55	3.55
09111902G pH 9 day 5 a	3.6	3.6	3.0	990
09111902G pH 9 day 5 b	2.4	2.4

table 2: The measured concentrations and the decrease in tier 1:

Parameter	pH 4.0	pH 7.0	pH 9.0
cm0 h	1500	1500	1500
cm120 h Mean	1020	1150	990
c after 5 days (% of start concentration)	68 %	77 %	66 %
Decrease	32 %	23 %	34 %

Validity criteria fulfilled:

yes

Conclusions:

The test shows that the test item hydrolyses depending on the pH value. The 50 % hydrolyses at pH 4 and pH 7 are estimated to be in a range between 7 and 8 days.

Executive summary:

The pre-test indicates that is substance is not resistant against hydrolysis. Since the substance is readily biodegradable, no further testing is required.

Tiers 2 and 3 were not conducted on request of the sponsor.

Description of key information

Recovery Rate (20°C, 5d) in % : 68 (pH 4); 77 (pH 7).
Half-life for hydrolyses (estimation): 7.5 d (pH 4); 7.2 (pH 7).

Key value for chemical safety assessment

Half-life for hydrolysis:

7.5 d

at the temperature of:

20 °C

Additional information

The pre-test indicates that is substance is not resistant against hydrolysis. Since the substance is readily biodegradable, no further testing is required.

The hydrolysis behaviour is not relevant for the classification. The substance is readily biodegradable.