Dibutyldimethoxystannane

Hydrolysis

Administrative data

Endpoint:

hydrolysis

Type of information:

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

Adequacy of study:

supporting study

Study period:

Not reported.

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: An internal company study conducted to a good scientific standard with a reasonable level of reporting. Study read across from other dioctyltin compounds.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2003

Report date:

2003

Materials and methods

Test guideline

Qualifier:

no guideline available

Principles of method if other than guideline:

Electrospray ionization mass spectrometry (ESI/MS) was used to determine whether dioctyltin compounds in water behave like dibutyltin compounds and form oxides relatively quickly. Dioctyltin bis(2-ethylhexylthioglycolate) (DOT(EHTG)2) and dioctyltin dichloride (DOTCl2) were studied. Dioctyltin oxide (DOTO) was also of interest but no detectable amount could be dissolved in any solvent.

The following studies were performed:
1. Identify the species present in solutions of DOT(EHTG)2 and DOTCl2 and estimate the sensitivity of ESI/MS for these compounds. In this case acetonitrile solutions mixed with water just before analysis.
2. Determine whether DOT(EHTG)2 and DOTCl2 in mixed organic/water solutions hydrolyze to form oxides.
3. For DOT(EHTG)2 and DOTCl2 in contact with water, identify the species present in the water.

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

Automatically generated during migration to IUCLID 6, no data available

IUPAC Name:

Automatically generated during migration to IUCLID 6, no data available

Details on test material:

Several dicotyltin compounds.

Radiolabelling:

no

Study design

Analytical monitoring:

yes

Details on sampling:

- Sampling intervals for the parent/transformation products:
Ca. 24 hours

- Sampling method:
not reported.

- Sampling methods for the volatile compounds, if any:
not applicable.

- Sampling intervals/times for pH measurements:
not applicable.

- Sampling intervals/times for sterility check:
not applicable.

- Sample storage conditions before analysis:
not applicable, samples analysed immediately.

- Other observation, if any (e.g.: precipitation, color change etc.):
none reported.

Buffers:

not applicable.

Estimation method (if used):

not applicable.

Details on test conditions:

TEST SYSTEM
- Sample Preparation:
Stock solutions of DOT(EHTG)2 and DOTCl2 were prepared containing 100µg/ml (as Sn) in acetonitrile (ACN).

Standards containing 125 ng/ml to 1000 ng/ml (as Sn) of either DOT(EHTG)2 or DOTCl2 were prepared from the stock solutions in polyethylene bottles by diluting with acetonitrile. Each standard was mixed 1:1 with water immediately prior to analysis using ESI/MS.

Water contact samples were prepared by adding the appropriate amount of stock solution to a polyethylene bottle and evaporating the solvent with nitrogen. This left a film of the corresponding dioctyltin compound on the walls of the bottle. Water was than added and the sample shaken for about three hours using a mechanical shaker, then the sample was allowed to sit. After the 24-hour contact time had passed, the samples were ultracentrafuged to remove any microemulsions or suspended particles. An aliquot of each sample was mixed 1:1 with acetonitrile immediately prior to analysis.
These standard stock solutions were used as anlytical standards in the main test.

- Hydrolysis in 1:1 Acetonitrile:Water Solutions:
Fresh 1000 ng/ml standard solutions of DOT(EHTG)2 and DOTCl2 were prepared, mixed 1:1 with water, and immediately analyzed using ESI/MS. These solutions were reanalyzed after 6 and 24 hours to follow the hydrolysis reaction. The results are listed in Table 4 for DOT(EHTG)2 and Table 5 for DOTCl2. The intensity of each species (measured by the height of the largest peak in the tin isotope cluster) was normalized to the most intense tin peak in the initial analysis.

Duration of test

Duration:

24 h

Number of replicates:

not reported.

Positive controls:

no

Negative controls:

no

Statistical methods:

not applicable.

Results and discussion

Preliminary study:

not applicable.

Transformation products:

yes

Identity of transformation products

Identity of transformation products 1

No.:

#1

Reference

Reference substance name:

Unnamed

IUPAC name:

(Oct)2SnO + H^+ + ACN

Identifier:

other: Chemical formula

Identity:

(Oct)2SnO + H^+ + ACN

Identity of transformation products 2

No.:

#2

Reference

Reference substance name:

Unnamed

IUPAC name:

(EHTG)2 + Na^+

Identifier:

other: Chemical formula

Identity:

(EHTG)2 + Na^+

Identity of transformation products 3

No.:

#3

Reference

Reference substance name:

Unnamed

IUPAC name:

(Oct)2Sn(SCH2COO) + H^+

Identifier:

other: Chemical formula

Identity:

(Oct)2Sn(SCH2COO) + H^+

Identity of transformation products 4

No.:

#4

Reference

Reference substance name:

Unnamed

IUPAC name:

(Oct)2Sn(SCH2COOH) + Na^+

Identifier:

other: Chemical formula

Identity:

(Oct)2Sn(SCH2COOH) + Na^+

Identity of transformation products 5

No.:

#5

Reference

Reference substance name:

Unnamed

IUPAC name:

(EHTG)2 + Na^+ + ACN

Identifier:

other: Chemical formula

Identity:

(EHTG)2 + Na^+ + ACN

Identity of transformation products 6

No.:

#6

Reference

Reference substance name:

Unnamed

IUPAC name:

(Oct)2Sn(SCH2COO) + H^+ + ACN

Identifier:

other: Chemical formula

Identity:

(Oct)2Sn(SCH2COO) + H^+ + ACN

Identity of transformation products 7

No.:

#7

Reference

Reference substance name:

Unnamed

IUPAC name:

(Oct)2Sn(EHTG)^+

Identifier:

other: Chemical formula

Identity:

(Oct)2Sn(EHTG)^+

Identity of transformation products 8

No.:

#8

Reference

Reference substance name:

Unnamed

IUPAC name:

(Oct)2Sn(EHTG)^+ + ACN

Identifier:

other: Chemical formula

Identity:

(Oct)2Sn(EHTG)^+ + ACN

Identity of transformation products 9

No.:

#9

Reference

Reference substance name:

Unnamed

IUPAC name:

(Oct)2Sn(EHTG)2 + Na^+ + ACN

Identifier:

other: Chemical formula

Identity:

(Oct)2Sn(EHTG)2 + Na^+ + ACN

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

- Hydrolysis in 1:1 Acetonitrile:Water Solutions:
Fresh 1000 ng/ml standard solutions of DOT(EHTG)2 and DOTCl2 were prepared, mixed 1:1 with water, and immediately analyzed using ESI/MS. These solutions were reanalyzed after 6 and 24 hours to follow the hydrolysis reaction. The results are listed in Table 4 for DOT(EHTG)2 and Table 5 for DOTCl2. The intensity of each species (measured by the height of the largest peak in the tin isotope cluster) was normalized to the most intense tin peak in the initial analysis.

For DOT(EHTG)2, the parent compound (mass 755) and the others which contain EHTG (masses 549, 590) show the most pronounced intensity loss with time (about a two-thirds decrease). By contrast, the free EHTG (masses 429, 470) shows an increase in intensity by approximately a factor of three. The oxide peak intensity (mass 404) remained about the same. DOTCl2 follows the same trend as DOT(EHTG)2 but the decrease in the parent compound is smaller over the same time frame.

It is evident from the DOT(EHTG)2 data that the stabilizer is hydrolyzing with time, noted especially by the increase in the EHTG peak. While the oxide peak at mass 404 does not increase, this may be a solubility issue. The oxide may already be at saturation concentration in the solution. This is supported by the fact that the absolute intensity of the mass 404 peak is about the same in the initial DOT(EHTG)2 and DOTCl2 analyses.

- Water Contact:
ESI/MS spectra from the 24-hour contact study are shown in Figure 5 for DOT(EHTG)2 and Figures 6 and 7 for DOTCl2. Only the oxide (mass 404) is visible in the DOT(EHTG)2 spectrum, while both the oxide and the parent chloride are present in the DOTCl2 spectra. This indicates the DOTCl2 has some solubility in water.

It is difficult to determine the amount of oxide present in the water contact samples because standards of DOTO cannot be made. Using DOT(EHTG)2 and DOTCl2 as surrogate standards is complicated by the fact that they show multiple species when analyzed using ESI/MS and the relative ratio of those species change with concentration. Additionally, it is not known if all the species have the same ionization efficiency as the oxide.

The concentration of oxide in the water contact samples was estimated from the DOT(EHTG)2 and DOTCl2 standards, using the intensity of the mass 404 oxide peak relative to the total intensity of all the tin species. The oxide concentration is estimated as 10 – 40 ng/ml for DOT(EHTG)2 and 30 – 120 ng/ml for DOTCl2.

Other kinetic parameters:

The analytical standard solutions were analysed immediately after the water was added. In all samples we observe hydrolysis products under these very short times. In particular, at 125 ng/ml (as Sn), almost all of the parent compound has converted to the oxide in less than 10 minutes (estimated).

Details on results:

INSTRUMENT SENSITIVITY
Standards containing DOT(EHTG)2 in the concentration range of 125 ng/mL to 1000 ng/mL were analyzed using ESI/MS in both the positive and negative ionization modes. No tin species were detected for DOT(EHTG)2 in the negative mode. The 125 ng/ml and 1000 ng/ml spectra for each sample were set at the same scale so that relative intensities could be compared.

The spectra indicate that the sensitivity of ESI/MS is better than 100 ng/mL. At 1000 ng/mL, the parent compound is most intense, although the oxide is visible. As the tin concentration decreases to 125 ng/mL, the oxides become more predominant. While the tin concentration decreases 8 fold, the oxide intensities hardly change. This is similar to the trends found with the dibutyltin stabilizer and may indicate the oxide is at saturation concentration.

The solutions were analysed immediately after the water was added, the analyses provide an indication of the speed of hydrolysis. In all samples hydrolysis products were observed under very short times. In particular, at 125 ng/ml (as Sn), almost all of the parent compound has converted to the oxide in less than 10 minutes (estimated).

HYDROLYSIS IN 1:1 ACETONITRILE:WATER SOLUTIONS
Fresh 1000 ng/mL standard solutions of DOT(EHTG)2 were prepared, mixed 1:1 with water, and immediately analyzed using ESI/MS. These solutions were reanalysed after 6 and 24 hours to follow the hydrolysis reaction.

The parent compound (mass 755) and the others which contain EHTG (masses 549, 590) gave the most pronounced intensity loss with time (about a two-thirds decrease). By contrast, the free EHTG (masses 429, 470) showed an increase in intensity by approximately a factor of three. The oxide peak intensity (mass 404) remained about the same.

It was apparent the stabiliser was hydrolysing with time, noted especially by the increase in the EHTG peak. While the oxide peak at mass 404 did not increase, this may be attributed to solubility. The oxide may have already reached saturation concentration in the solution. This is supported by the fact that the absolute intensity of the mass 404 peak is about the same in the initial DOT(EHTG)2 and DOTCl2 analyses.

WATER CONTACT
Only the oxide (mass 404) was visible in the DOT(EHTG)2 spectrum.

It is difficult to determine the amount of oxide present in the water contact samples because standards of DOTO cannot be made. Using DOT(EHTG)2 as a surrogate standards is complicated by the fact that it shows multiple species when analysed using ESI/MS and the relative ratio of those species change with concentration. Additionally, it is not known if all the species have the same ionization efficiency as the oxide.

The concentration of oxide in the water contact samples was estimated from the DOT(EHTG)2 standards, using the intensity of the mass 404 oxide peak relative to the total intensity of all the tin species. The oxide concentration is estimated at 10 – 40 ng/mL for DOT(EHTG)2.

Any other information on results incl. tables

Table 2: Species found for (Oct)₂Sn(EHTG)₂

Ion	Ion Mass (m/z)	MS mode
Unknown: Sn + Cl	315	ESI(+)
(Oct)2SnO + H^++ ACN	404	ESI(+)
(EHTG)2+ Na^+	429	ESI(+)
(Oct)2Sn(SCH2COO) + H^+	437	ESI(+)
(Oct)2Sn(SCH2COOH) + Na^+	460	ESI(+)
(EHTG)2+ Na^++ ACN	470	ESI(+)
(Oct)2Sn(SCH2COO) + H^++ ACN	478	ESI(+)
(Oct)2Sn(EHTG)^+	549	ESI(+)
(Oct)2Sn(EHTG)^++ ACN	590	ESI(+)
(Oct)2Sn(EHTG)2+ Na^++ ACN	775	ESI(+)

Table 3: Ion intensity change with time for (Oct)₂Sn(EHTG)₂

Ion	Ion Mass (m/z)	Initial Relative Intensity	6 hour Relative Intensity	24 hour Relative Intensity
(Oct)2SnO + H^++ ACN	404	11	11	12
(EHTG)2+ Na^+	429	32	75	102
(Oct)2Sn(SCH2COO) + H^+	437	44	35	23
(Oct)2Sn(SCH2COOH) + Na^+	460	19	15	11
(EHTG)2+ Na^++ ACN	470	24	45	67
(Oct)2Sn(SCH2COO) + H^++ ACN	478	83	51	32
(Oct)2Sn(EHTG)^+	549	44	21	11
(Oct)2Sn(EHTG)^++ ACN	590	18	7	6
(Oct)2Sn(EHTG)2+ Na^++ ACN	775	100	66	39

Applicant's summary and conclusion

Validity criteria fulfilled:

not applicable

Conclusions:

Dioctyltins hydrolyse in acetonitrile/water solutions to form dioctyltin oxide. It was determined that contact of these dioctyltins with water alone produces the oxide. In addition, the following conclusions were made:

The detection of the octyltin species in the solutions depends on the ionization procedure used for the mass spectral analysis. For example, the positive ion mode allows for the detection of the oxide and the dioctyltin monochloride, whereas the dioctyltin dichloride is only seen in the negative ion mode where the oxide is not observed.

The species observed in solution depends on the solution make up. In acetonitrile/water solutions, where there is a significant amount of organic solvent, the presence of the parent EHTG stabilisers as well as the oxide are observed. In the water contact experiments, no EHTG stabilizer is observed in solution, only oxide.

The results indicate that these dioctyltin compounds behave like their dibutyltin counterparts and readily form oxides when in contact with water.

Executive summary:

The purpose of the current study was to determine whether dioctyltin compounds exhibit the same behaviour as dibutyltin compounds in the presence of water. The results indicate that these dioctyltin compounds behave like their dibutyltin counterparts and readily form oxides when in contact with water. In addition, the following conclusions were made:

The detection of the octyltin species in the solutions depends on the ionization procedure used for the mass spectral analysis. For example, the positive ion mode allows for the detection of the oxide and the dioctyltin monochloride, whereas the dioctyltin dichloride is only seen in the negative ion mode where the oxide is not observed.

The species observed in solution depends on the solution make up. In acetonitrile/water solutions, where there is a significant amount of organic solvent, the presence of the parent EHTG stabilisers as well as the oxide are observed. In the water contact experiments, no EHTG stabilizer is observed in solution, only oxide.