Tetrabutylphosphonium bromide

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

2014

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: In accordance with test guidelines EC C.7 and OECD 111. The study has not been performed under GLP.

Qualifier:

according to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Version / remarks:

(2004)

Qualifier:

according to guideline

Guideline:

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

GLP compliance:

no

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

Sampling time: t= 120 hours

Buffers:

Certified pH 4.0, 7.0 and 9.0 buffer solutions purchased from Fischer Scientific (pH 4: potassium acid phthalate; pH 7: potassium phosphate monobasic and sodium hydroxide, chlorine titrimeter reagent; pH 9: boric acid, potassium chloride, and sodium hydroxide) were vacuum filtered through sterile Thermo Scientific Nalgene Disposable Filter Units (Pore Size: 0.10 μm). These solutions were then sonicated for 5 minutes and bubbled with nitrogen for 5 minutes.

Details on test conditions:

Tier 1 preliminary test was performed at pH 4, 7 and 9 at 50 ± 0.5°C.

Sample solutions to be incubated were prepared at 3.0 mg/mL in sterile volumetric flasks with the three buffer solutions. The sample solutions were then placed into sterile Thermo ScientificTM depyrogenated vials (Type 1 borosilicate glass, assembled with butyl stoppers and aluminum seals) using sterile syringes and sterile needles, and were incubated at 50 ± 0.5°C for 120 hrs. Aluminum foil was wrapped around the vials to shield the sample from light.

After 120 hours, the incubated samples were diluted by a factor of two in methanol. End solution: 50/50 (v/v) buffer/methanol.

Time 0 standards and matrix blanks at the three buffer pHs were prepared in a simliar fashion as described for the incubated samples.

Positive controls:

no

Negative controls:

no

Preliminary study:

At pH 4, 7 and pH 9, peak area decrease (hydrolysis) of < 10% was observed after 5 day. This corresponds with a half-life time at 25°C of > 1 year. According to the guideline, no further tests were required.

Details on results:

The attachment show overlaid HPLC/CAD chromatograms of the blank, sample at time 0, and incubated sample at pHs 4, 7, and 9 respectively.

Table: Peak areas and changes in peak areas between time 0 and time 120 hrs samples.

Sample	Peak Area	Corrected Peak Area *	% Change in Peak Area
Time 0, pH 4	2293.3	2272.1	+ 0.6 **
Time 120 hrs, pH 4	2263.8	2285.1
Time 0, pH 7	2316.7	2310.5	+ 3.0 **
Time 120 hrs, pH 7	2392.7	2380.0
Time 0, pH 9	2304.8	2274.5	+ 0.8 **
Time 120 hrs, pH 9	2317.6	2293.1

* Peak area as corrected for differences in concentration due to different masses weighed of the samples.

** While it is expected that the % change in peak area would be negative if the sample is hydrolyzing, these positive values are within instrument error.

Validity criteria fulfilled:

yes

Conclusions:

At pH 4, 7 and 9 and 50°C, a degree of hydrolysis of < 10% was observed after 120 hours (5 days). This corresponds with a half-life time at 25°C of > 1 year; the substance is hydrolytically stable at pH 4, 7 and 9.

Executive summary:

The rate of hydrolysis of the substance at pH values normally found in the environment (pH 4-9) was determined in Tier 1 study according to EC C.7 and OECD 111 guidelines. At pH 4, 7 and 9 and 50°C, a degree of < 10% of hydrolysis was observed after 5 days. This corresponds with a half-life time at 25°C of > 1 year; the substance can be considered hydrolytically stable at pH 4, 7 and 9.

Description of key information

The substance has no readily hydrolysable groups and is therefore not expected to hydrolyse. The result of a non-GLP Tier 1 study confirmed this. The rate of hydrolysis of the substance at pH 4-9 was determined in a Tier 1 study according to EC C.7 and OECD 111 guidelines. At pH 4, 7 and 9 and 50°C, a degree of < 10% of hydrolysis was observed after 5 days. This corresponds with a half-life time at 25°C of > 1 year; the substance can be considered hydrolytically stable at pH 4, 7 and 9.

Additional information

Key value for CSA: half-life time at 25°C of > 1 year