2-ethylhexyl 10-ethyl-4,4-dimethyl-7-oxo-8-oxa-3,5-dithia-4-stannatetradecanoate

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

16 January 2015 to 03 January 2017

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)

Version / remarks:

2004

Deviations:

no

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

no

Remarks:

GLP is not required for this non-animal study

Radiolabelling:

no

Analytical monitoring:

yes

Buffers:

pH 1.2: 0.1 M HCl
pH 4.0: HCl / NaCl / Citric acid
pH 7.0: Na2HPO4 / NaH2PO4
pH 9.0: H3BO3 / KCl / NaOH

Details on test conditions:

TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: 250 mL Erlenmeyer flask with ground-in stopper.
- Measures to exclude oxygen: Ground-in stopper.


TEST MEDIUM
- The test material was used without a co-solvent or a detergent.
- One g (1.8 mMol) test material was added to 100 mL of 0.1 M aqueous solution of hydrochloric acid that was preheated to 37 °C in a 250 mL Erlenmeyer flask with ground-in stopper. For the initial time of the experiment (30 seconds), the reaction products were extracted with hexane immediately according to the procedure described below.
- For longer exposure/hydrolysis times, the flask was closed with a stopper and heated on a heating cabinet for 0.5, 1, 2, 4, and 72 hours at 37 °C. The mixture was stirred by a magnetic stirrer using a 40x7 mm stir bar at approximately 100 rpm.
- After the pre-determined exposure time, the solution was allowed to cool down to room temperature; extracted 2 times with 25 mL hexane; the phases were separated using a separatory funnel. The organic phase was transferred into a pre-weighed flask, and the solvent was removed in a rotary evaporator (< 40 °C, 10 mbar). The weight difference was recorded for the mass balance, and the samples were analysed by 119Sn­NMR Spectroscopy.
- One g (1.8 mMol) of the test material was added to 100 mL of the respective buffer solution in a 250 mL Erlenmeyer flask. The flask was closed with a stopper and heated in a heating cabinet for 5 days (120 hours) at 50 °C. The mixture was stirred by a magnetic stirrer using a 40x7 mm stir bar at approx. 100 rpm. The test was carried out at pH 1.2 and 37 °C.
- After the pre-determined time, the reaction mixture was allowed to cool down to room temperature extracted with 20 mL hexane, the phases were separated using a separatory funnel. The organic phase was transferred into a pre­weighed flask and the solvent was removed in a rotary evaporator (< 40 °C, 10 mbar). The weight difference was recorded for the mass balance, and the samples were analysed by 119Sn-NMR.
- The water phase was analysed by AAS for a total tin content.

Duration:

30 s

pH:

1.2

Temp.:

37 °C

Initial conc. measured:

10 g/L

Duration:

30 min

pH:

1.2

Temp.:

37 °C

Initial conc. measured:

10 g/L

Duration:

1 h

pH:

1.2

Temp.:

37 °C

Initial conc. measured:

10 g/L

Duration:

2 h

pH:

1.2

Temp.:

37 °C

Initial conc. measured:

10 g/L

Duration:

4 h

pH:

1.2

Temp.:

37 °C

Initial conc. measured:

10 g/L

Duration:

72 h

pH:

1.2

Temp.:

37 °C

Initial conc. measured:

10 g/L

Duration:

120 h

pH:

4

Temp.:

50 °C

Initial conc. measured:

10 g/L

Duration:

120 h

pH:

7

Temp.:

50 °C

Initial conc. measured:

10 g/L

Duration:

120 h

pH:

9

Temp.:

50 °C

Initial conc. measured:

10 g/L

Number of replicates:

The experiments were run in duplicate.

Positive controls:

no

Negative controls:

no

Transformation products:

yes

No.:

#1

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

- Formation and decline of each transformation product during test: The results show that the only product that is formed as a result of the in vitro metabolism is DMTEC, a mono-chloro ester of the test material.
The hydrolysis starts instantly when the test material is brought in contact with the HCl solution. Even after 30 seconds (followed by the "instant" work-up) the DMTEC concentration raised from 3.5 % in the untreated test material to 13.7 %.
After 30 minutes the concentration of DMTEC in the reaction mass reaches 25 %. The subsequent increase in the concentration of DMTEC is very moderate, and it reached 29 % after 72 hours.

% Recovery:

>= 88 - <= 98.4

pH:

1.2

Temp.:

37 °C

Duration:

>= 1 - <= 72 h

Remarks on result:

other: St. dev. not reported.

pH:

4

Temp.:

50 °C

DT50:

> 120 h

Type:

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

Remarks on result:

other: St. dev. not reported

pH:

7

Temp.:

50 °C

DT50:

> 120 h

Type:

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

Remarks on result:

other: St. dev. not reported.

pH:

9

Temp.:

50 °C

DT50:

> 120 h

Type:

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

Remarks on result:

other: St. dev. not reported.

Details on results:

- Mass balance at pH 1.2: For each tested 1 g (1.8 mmol) sample of the test material, the test material was added to a preheated (37 °C) solution of hydrochloric acid. The Recovered Weight was converted to the Adjusted Recovery per cent taking into consideration amounts of the formed DMTEC. Results show that except for the first two short experiments, the adjusted recovery per cent was high, ranging from 88.0 to 98.4 %.
- Hydrolysis at pH 4.0, 7.0, and 9.0: Samples of the test material were added to the respective buffer solutions at 50 °C for 5 days (120 h). The reaction products were extracted with hexane. The 119Sn-NMR spectra of the extracted reaction products did not show any sign of hydrolysis.
- Mass balance at pH 4, 7, 9: For each tested pH value, a 1 g (1.8 mmol) sample of the test material was added to the respective buffer solution. After the required hydrolysis period of 5 days, amounts of the hydrolysate were recovered via hexane extraction from the aqueous phase.
The mass balance showed a high recovery of the initial material of the test material after completing the hydrolysis test over the required period (5 days) and followed by the extraction with hexane.
- Tin in aqueous phase: After completing the hydrolyses at the specified pH values the aqueous phases were analysed for total tin content by AAS. The results show that water-soluble tin compounds were only present in trace amounts in the reaction mixture after completing the hydrolysis test followed by the extraction with hexane. The low tin content values do not indicated about the formation of water soluble tin compounds in significant amounts.

Kinetics of the test material in vitro metabolism

Test-No.	Time (h)	DMTE (%w/w)	DMTEC (%w/w)
AK/114/089/01	0	92.9 %	3.5 %
W54-174L/M	0.001	82.3 %	13.7 %
W54-174C/D	0.5	68.7 %	25.0 %
W54-174I/K	1	69.5 %	23.0 %
W54-174G/H	2	68.3 %	25.0 %
W54-174E/F	4	69.2 %	24.0 %
W54-174A/B	72	61.8 %	29.0 %

* No signal typical for DMTC was detected. 

Recovery of test material

Test-No.	Time of Hydrolysis [h]	Recovered Weight [g]	Concentration of Formed DMTEC	Adjusted Recovery
W54-174L	0.001	0.61	10.4 %	63.0 %
W54-174M	0.001	0.62	10.0 %	63.9 %
WS4-174C	0.5	0.92	21.8 %	98.4 %
W54-174D	0.5	0.91	21.3 %	97.2 %
W54-174I	1	0.81	16.5 %	85.2 %
W54-174K	1	0.90	22.7 %	96.6 %
W54-174G	2	0.89	18.5 %	94.2 %
W54-174H	2	0.85	24.7 %	91.8 %
W54-174E	4	0.86	19.1 %	91.2 %
W54-174F	4	0.84	22.0 %	89.9 %
W54-174A	72	0.81	28.4 %	88.5 %
W54-174B	72	0.82	22.8 %	88.0 %

 

Recovery of the test material

No.	pH	Initial Mass	Recovered	Recovery Rate
W57-053-D	4	1.0 g	0.89	89 %
W57-053-E	7	1.0 g	0.98	98 %
W57-053-F	9	1.0 g	0.75	75 %

 

Tin content in remaining aqueous phases

No.	pH	Tin Content
W57-053-D	4	215 mg/L
W57-053-E	7	60 mg/L
W57-053-F	9	195 mg/L

Chemical shifts (ppm) illustrating kinetics of the test material in vitro metabolism

Test- No.	Time h	δ DMTE	δ MMTE	δ DMTEC	δ MMTEC
W54-174 L	0.001	74.4	67	41.32
W54- 174 M	0.001	74.15	66.88	40.95
W54-174 C	0.5	74.11	66.66	40.86
W54-174 D	0.5	73.27	65.89	40.08
W54-174 I	1	73.47	66	40.33
W54-174 K	1	74.31	66.69	41.14
W54-174 G	2	74.29	66.76	41.2
W54-174 H	2	74.59	66.91	41.7
W54-174 E	4	73.57	66.02	40.51
W54-174 F	4	74.23	66.67	41.08
W54-174 A	72	74.41	66.83	41.47	-12.67
W54-174 B	72	74.25	66.76	41.23	-12 .96

 

Relative intensities and concentrations illustrating kinetics of DMTC in-vitro metabolism

		DMTE		MMTE		DMTEC		MMTEC
Test-No.	Time h	Mol %	% w/w	Mol %	% w/w	Mol %	% w/ w	Mol %	% w/w
AK/14/089/01	0	92.2	92.9	4.9	3.7	2.4	3.5	ND*	ND
W54- 174 L	0.001	84	82.2	5.3	3.9	9.9	13.9	ND	ND
W54- 174 M	0.001	84	82.4	5.6	4.1	9.6	13.5	ND	ND
W54-174 C	0.5	73.2	69.0	8.1	5.7	18.7	25.3	ND	ND
W54-174 D	0.5	72	68.3	9.8	6.9	18.2	24.7	ND	ND
W54-174 I	1	75	72.4	10.6	7.6	14.4	19.9	ND	ND
W54-174 K	1	70.4	66.6	10.3	7.3	19.3	26.1	ND	ND
W54-174 G	2	74	70.9	10	7.2	16	22.0	ND	ND
W54-174 H	2	70.3	65.8	8.7	6.1	21	28.1	ND	ND
W54-174 E	4	74.1	70.7	9.4	6.7	16.5	22.6	ND	ND
W54-174 F	4	71.5	67 .7	9.7	6.9	18.8	25.5	ND	ND
W54- 174 A	72	61.9	57.8	12.5	8.7	23.8	31.8	1.8	1.6
W54- 174 B	72	69.7	65.8	9.7	6.8	19.4	26.2	1.3	1.2

* ND = Not detected

Validity criteria fulfilled:

not specified

Conclusions:

Under the simulated gastric conditions the test material in vitro metabolism equilibrated within a short period and resulted in the formation of DMTEC (amono-chloro-ester of the test material) at about 30 %.
At higher pH values (4, 7, 9) no spectroscopic indications for a breakdown product have been detected in the hexane extracts of the reaction mixtures.
Low tin contents of the remaining aqueous phases together with the spectroscopic results demonstrate the high hydrolytic stability of the test materials at higher pH values.

Executive summary:

The hydrolysis as function of pH of the test material was assessed according to OECD Test Guideline 111 and EU Method C.7. 

The hydrolysis as function of pH can be monitored using 119Sn­NMR Spectroscopy by the decrease in the relative intensity of the respective 119Sn-NMR signal at ~74 ppm attributable to the test material and the increase of the signal at ~41 ppm characteristic to DMTEC.

Under the simulated gastric conditions (0.1 M HCl/pH 1.2 /37 °C) the test material in vitro metabolism equilibrated within a short period and resulted in the formation of DMTEC (a mono-chloro-ester of the test material) at about 30 %.

DMTC was not detected in any of the metabolised test material samples at δDMTC = 131 ppm using the 119Sn-NMR spectroscopy.

At higher pH values (4, 7, 9) no spectroscopic indications for a breakdown product have been detected in the hexane extracts of the reaction mixtures.

Low tin contents of the remaining aqueous phases together with the spectroscopic results demonstrate the high hydrolytic stability of the test items at higher pH values.

The results are congruent with earlier studies on other alkyltin thioglycolates.

Description of key information

Under the simulated gastric conditions the test material in vitro metabolism equilibrated within a short period and resulted in the formation of DMTEC (amono-chloro-ester of the test material) at about 30 %.

At higher pH values (4, 7, 9) no spectroscopic indications for a breakdown product have been detected in the hexane extracts of the reaction mixtures.

Low tin contents of the remaining aqueous phases together with the spectroscopic results demonstrate the high hydrolytic stability of the test materials at higher pH values.

Additional information

The hydrolysis as function of pH of the test material was assessed according to OECD Test Guideline 111 and EU Method C.7.  The study was awarded a reliability score of 1 in accordance with the criteria set forth by Klimisch et al. (1997).

The hydrolysis as function of pH can be monitored using 119Sn­ NMR Spectroscopy by the decrease in the relative intensity of the respective 119Sn-NMR signal at ~74 ppm attributable to the test material and the increase of the signal at ~41 ppm characteristic to DMTEC.

Under the simulated gastric conditions (0.1 M HCl/pH 1.2 /37 °C) the test material in vitro metabolism equilibrated within a short period and resulted in the formation of DMTEC (a mono-chloro-ester of the test material) at about 30 %.

DMTC was not detected in any of the metabolised test material samples at δDMTC = 131 ppm using the 119Sn-NMR spectroscopy.

At higher pH values (4, 7, 9) no spectroscopic indications for a breakdown product have been detected in the hexane extracts of the reaction mixtures.

Low tin contents of the remaining aqueous phases together with the spectroscopic results demonstrate the high hydrolytic stability of the test items at higher pH values.

The results are congruent with earlier studies on other alkyltin thioglycolates.