Tris(2-methylphenyl)phosphine

Biodegradation in water: screening tests

Administrative data

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

21 Aug 2017 to 12 Nov 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2018

Report date:

2018

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

Deviations:

yes

Remarks:

None of the deviations were considered to have impacted the overall integrity of the study or the interpretation of the study results and conclusions.

Test guideline 2

Qualifier:

according to guideline

Guideline:

other: ISO International Standard 10634. "Water Quality - Guidance for the preparation and treatment of poorly water-soluble organic compounds for the subsequent evaluation of their biodegradability in an aqueous medium", (1995).

Deviations:

yes

Remarks:

None of the deviations detailed in the study report were considered to have impacted the overall integrity of the study or the interpretation of the study results and conclusions.

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

Tris(2-methylphenyl)phosphine

EC Number:

228-193-9

EC Name:

Tris(2-methylphenyl)phosphine

Cas Number:

6163-58-2

Molecular formula:

C21H21P

IUPAC Name:

tris(2-methylphenyl)phosphane

Test material form:

solid: particulate/powder

Details on test material:

Lot number: 2000850599
Analysis date: 19 August 2016

Specific details on test material used for the study:

Appearance: Off-white crystalline powder (determined by Charles River Den Bosch)
Batch: B64002 (Pfizer Lot no. 2000850599)
Test item storage: At room temperature
Stable under storage conditions until: Unknown

Study design

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

Source: The source of test organisms was activated sludge freshly obtained from a municipal sewage treatment plant: 'Waterschap Aa en Maas', 's-Hertogenbosch, The Netherlands, receiving predominantly domestic sewage.

Treatment: The freshly obtained sludge was used immediately. The concentration of suspended solids was determined to be 4.9 g/L. Before use, the sludge was allowed to settle (approximately 30 minutes)
and the supernatant liquid was used as inoculum at the amount of 10 mL/L of mineral medium.

Reason for selection: The test has been accepted internationally for determining the 'ready' biodegradability of test items under aerobic conditions.

Pre-incubation medium: The day before the start of the test (day -1) mineral components, Milli- RO water (ca. 80% of final volume) and inoculum (1% of final volume) were added to each bottle. This mixture was aerated with synthetic air overnight to purge the system of CO2
.

Duration of test (contact time):

28 d

Initial test substance concentration

Initial conc.:

ca. 14.5 mg/L

Based on:

test mat.

Remarks:

corresponding to 12 mg TOC/L

Parameter followed for biodegradation estimation

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
Test vessels: 2 litre brown coloured glass bottles.
Milli- RO water: Tap-water purified by reverse osmosis (Milli- RO) and subsequently passed over activated carbon.
Stock solutions of mineral components A) 8.50 g KH2PO4
21.75 g K2HPO4
62.20 g Na2HPO4.12H20
0.50 g NH4Cl
dissolved in Milli- RO water and made up to 1 litre, pH 7.4 ± 0.2
B)22.50 g MgSO4.7H2O dissolved in Milli- RO water and made up to 1 litre.
C)36.40 g CaCl2.2H2O dissolved in Milli- RO water and made up to 1 litre.
D)0.25 g FeCl3.6H2O dissolved in Milli- RO water and made up to 1 litre.
Mineral medium: 1 litre mineral medium contains: 10 mL of solution (A), 1 mL of solutions (B) to (D) and Milli- RO water.
Barium hydroxide: 0.0125 M Ba(OH)2 (Boom, Meppel, The Netherlands),
stored in a sealed vessel to prevent absorption of CO2 from the air.
Synthetic air (CO2 < 1 ppm) A mixture of oxygen (ca. 20%) and nitrogen (ca. 80%) was passed through a bottle, containing 0.5 - 1 litre 0.0125 M Ba(OH)2 solution to trap CO2 which might be present in small amounts. The synthetic air was passed through the scrubbing solutions at a rate of approximately 1-2 bubbles per second (ca. 30-100 mL/min).
Illumination: The test media were excluded from light.

TEST SYSTEM
Source: The source of test organisms was activated sludge freshly obtained from a municipal sewage treatment plant: 'Waterschap Aa en Maas', 's-Hertogenbosch, The Netherlands, receiving predominantly domestic sewage.

Treatment: The freshly obtained sludge was used immediately. The concentration of suspended solids was determined to be 4.9 g/L (data obtained from the sewage treatment plant; see GLP deviation in the Compliance Statement). Before use, the sludge was allowed to settle (approximately 30 minutes) and the supernatant liquid was used as inoculum at the amount of 10 mL/L of mineral medium.

Reason for selection: The test has been accepted internationally for determining the 'ready' biodegradability of test items under aerobic conditions.

Preparation of Bottles
Pre-incubation medium: The day before the start of the test (day -1) mineral components, Milli- RO water (ca. 80% of final volume) and inoculum (1% of final volume) were added to each bottle. This mixture was aerated with synthetic air overnight to purge the system of CO2.

SAMPLING
Test item storage: At room temperature

CONTROLS
-1 positive control (sodium acetate) and
-1 toxicity control (Tri-o-tolylphosphine plus sodium acetate).

Reference substance

Reference substance:

other: Sodium acetate

Results and discussion

% Degradation

Parameter:

other: Relative Biodegradation %

Value:

3

Sampling time:

28 d

Remarks on result:

other:

Remarks:

The relative biodegradation values calculated from the measurements performed during the test period revealed no biologically significant biodegradation of Tri-o-tolylphosphine (3% and 0%, based on ThCO 2 ).

Details on results:

Theoretical CO2 Production
The ThCO2 of Tri-o-tolylphosphine was calculated to be 3.04 mg CO2/mg.
The ThCO2 of sodium acetate was calculated to be 1.07 mg CO2/mg

Biodegradation
The results of CO2 production and biodegradation in blank bottles, background bottles and each test bottle are listed in Table 2 to 8 in the results table attachments below.

Biodegradation of Tri-o-tolylphosphine and Sodium Acetate in the Modified Sturm Test
The relative biodegradation values calculated from the measurements performed during the test period revealed no biologically significant biodegradation of Tri-o-tolylphosphine (3% and 0%, based on ThCO2).

In the toxicity control, more than 25% biodegradation occurred within 14 days (41%, based on ThCO2). Therefore, the test item was assumed not to inhibit microbial activity.

Functioning of the test system was checked by testing the reference item sodium acetate, which showed a normal biodegradation curve

Monitoring of Temperature and pH
The temperature recorded in a vessel with water in the same room varied between 22 and 24°C.

Any other information on results incl. tables

Results tables can be found in the attachment below.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

In conclusion, Tri-o-tolylphosphine was not readily biodegradable under the conditions of the modified Sturm test presently performed.

Executive summary:

The objective of the study was to evaluate the non-volatile test item Tri-o-tolylphosphine for its ready biodegradability in an aerobic aqueous medium with microbial activity introduced by inoculation with the supernatant of activated sludge; Carbon dioxide (CO2) evolution test (modified Sturm test).

The study procedures described in this report were in compliance with the OECD guideline No. 301 B, 1992. In addition, the procedures were designed to meet the test methods of the ISO standard 10634, 1995.

Tri-o-tolylphosphine was an off-white crystalline powder with a purity of 99.9%. The test item was tested in duplicate at a target concentration of 14.5 mg/L, corresponding to 12 mg TOC/L. The organic carbon content was based on the molecular formula. The Theoretical CO2 production (ThCO2) of Tri-o-tolylphosphine was calculated to be 3.04 mg CO2/mg.

The study consisted of six bottles:

• 2 inoculum blanks (no test item),

• 2 test bottles (Tri-o-tolylphosphine),

• 1 positive control (sodium acetate) and

• 1 toxicity control (Tri-o-tolylphosphine plus sodium acetate).

Since Tri-o-tolylphosphine was not sufficiently soluble to allow preparation of an aqueous solution at a concentration of 1 g/L, weighed amounts were added to the 2-litres test bottles containing medium with microbial organisms and mineral components. To this end, 10 mL of Milli- RO  water was added to each weighing bottle containing the test item. After vigorous mixing (vortex) the resulting suspension was added quantitatively to the test medium. The test solutions were continuously stirred during the test to ensure optimal contact between the test item and test organisms. Furthermore, the test medium was daily swirled around, since the test item tended to float on the water surface. Test duration was 28 days for the inoculum blank and test item (last CO2 measurement on day 29) and 14 days for the positive and toxicity control (last CO2 measurement on day 15).

The relative biodegradation values calculated from the measurements performed during the test period revealed no biologically significant biodegradation of Tri-o-tolylphosphine (3% and 0%, based on ThCO2).

In the toxicity control, Tri-o-tolylphosphine was found not to inhibit microbial activity. Since all criteria for acceptability of the test were met, this study was considered to be valid. In conclusion, Tri-o-tolylphosphine was designated as not readily biodegradable.