Ethyltriphenylphosphonium iodide

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2003-03-18 to 2003-09-19

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

adopted July 17, 1992

Qualifier:

according to guideline

Guideline:

EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)

Version / remarks:

Publication No. L383, December 1992

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source: The source of test organisms was activated sludge freshly obtained from a municipal sewage treatment plant: 'Waterschap de Maaskant', 's-Hertogenbosch, the Netherlands.
- Pretreatment: The sludge was kept under continuous aeration until further treatment. The concentration of suspended solids was 2.4 g/L in the concentrated sludge (information obtained from the municipal sewage treatment plant). Before use, the sludge was allowed to settle (30-90 minutes) and the liquid decanted for use as inoculum at the amount of 12.5 ml/L of mineral medium.
- Concentration: 1% in test vessels

Duration of test (contact time):

28 d

Initial conc.:

21 mg/L

Based on:

act. ingr.

Initial conc.:

12 mg/L

Based on:

TOC

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS

- Composition of medium:
-- Milli-RO I Milli-Q water: Tap-water purified by reverse osmosis (MiIIi-RO) and subsequently passed over activated carbon and ionexchange cartridges (Milli-Q) (Millipor.e Corp., Bedford, Mass., USA).
-- Stock solutions of mineral components: A) 8.50 g KH2P04, 21.75 g K2HP04, 67.20 g Na2HP04.12H20, 0.50 g NH4CI dissolved in 1 L Milli-Q water, pH 7.4 ± 0.2
B) 22.50 g MgS04.7H20 dissolved in 1 L MiIIi-Q water.
C) 36.40 g CaCI2.2H20 dissolved in 1L MiIIi-Q water.
D) 0.25 9 FeCls.6H20 dissolved in 1 L Milli-Q water.
-- Mineral medium: 1 L mineral medium contains: 10 mL of solution (A), 1 mL of solutions (8) to (D) and Milli-RO water.
- Additional substrate: no
- Solubilising agent (type and concentration if used): no
- Test temperature: The temperature recorded in a vessel with water in the same room varied between 22.1 and 23.4°C.
- pH: 7.4 - 7.6 (test item), 7.4 - 7.6 (blanc control), 7.7 - 7.8 (positive control), 7.5 -7.8 (toxicity control)
- pH adjusted: no
- Aeration of dilution water: During the test period aeration and stirring took place.
- Suspended solids concentration: 1% in test vessels
- Continuous darkness: yes
- Generation of CO2-free air: A mixture of oxygen (21 %) and nitrogen (79%) was passed through a bottle, containing 0.5 - 1 litre 0.0125 M Ba(OH) solution to trap CO2 which might be present in small amounts. The CO2-free air was sparged through the scrubbing solutions at a rate of approximately 1-2 bubbles per second (ca. 30-100 mL/min).

TEST SYSTEM
- Culturing apparatus: 2 litre all-glass brown coloured bottles
- Number of culture flasks/concentration:
-- 2 blank controls (no test material),
-- 2 test bottles (test item, 21 mg/L),
-- 1 positive control (sodium acetate, 40 mg/L) and
-- 1 toxicity control (test item, 21 mg/L; plus sodium acetate, 40 mg/L).
- Method used to create aerobic conditions:
-- Pretest: The medium was aerated with CO2-free air overnight to purge the system of CO2.
-- During test: During the test period aeration and stirring took place.
- Preparation of bottles:
-- Pre-incubation medium: Mineral components, Milli-RO water (ca. 80% total volume) and inoculum (1% final volume) were added to each bottle. This mixture was aerated with CO2-free air overnight to purge the system of CO2.
-- Test bottles: The test item and positive control were added to the bottles containing the microbial organisms and mineral components (ca. 80% of total volume). The volumes of suspensions were made up to 2 litres with Milli-RO water, resulting in the mineral medium described before. The test item was not sufficiently soluble to allow preparation of a concentrated aqueous solution of 1 g/L and indicated to be light sensitive. Therefore, amounts of test substance were weighed in a room especially equipped with yellow light and shipped to the testing chamber in darkened bottles. Weighed amounts of test item were quantitatively added to the test bottles containing the microbial organisms and mineral components. 10 mL of milli-RO water was added to each weighing bottle and 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 substance and the test organisms.

SAMPLING, ANALYTICAL METHOD, DATA EVALUATION:
- Sampling method: Three CO2-absorbers (bottles filled with 100 mL 0.0125 M Ba(OH)2) were connected in series to the exit air line of each test bottle Sampling frequency: 0, 2, 5, 7, 9, 14, 19, 23, 27 and 29 days
- Measurement of CO2 production: The CO2 produced in each test bottle reacted with the barium hydroxide in the gas scrubbing bottle and precipitated out as barium carbonate. The amount of CO2 produced was determined by titrating the remaining Ba(OH) with 0.05 M standardized HCI.
- Sample storage before analysis: Titrations were made every second or third day during the first 10 days, and thereafter at least every fifth day until the 28th day. Each time the CO2-absorber nearest to the test bottle was removed for titration; each of the remaining two absorbers was moved one position in the direction of the test bottle. A new CO2-absorber was placed at the far end of the series. Phenolphthalein was used as pH-indicator. On the 28th day, the pH of the test suspensions was measured and 1 mL of concentrated HCI was added to each bottle. The bottles were aerated overnight to drive off CO2 present in the test suspension. The final titration was made on day 29.
- Significance: A figure of more than 10% degradation was considered as significant.
- Toxicity control: Toxicity control: if less than 25% degradation (based on ThC02) occurred within 14 days, the test substance can be assumed to be inhibitory.

Reference substance:

acetic acid, sodium salt

Parameter:

% degradation (CO2 evolution)

Value:

2

Sampling time:

2 d

Remarks on result:

other: mean of bottles A and B

Parameter:

% degradation (CO2 evolution)

Value:

3

Sampling time:

7 d

Remarks on result:

other: mean of bottles A and B

Parameter:

% degradation (CO2 evolution)

Value:

5

Sampling time:

14 d

Remarks on result:

other: mean of bottles A and B

Parameter:

% degradation (CO2 evolution)

Value:

5

Sampling time:

27 d

Remarks on result:

other: mean of bottles A and B

Key result

Parameter:

% degradation (CO2 evolution)

Value:

6

Sampling time:

29 d

Remarks on result:

other: mean of bottles A and B

Details on results:

Theoretical CO2 production:
The Theoretical CO2 production (ThCO2) of the test item was calculated to be 2.10 mg CO2/mg.
The concentration was 41.7 (A) and 41.9 mg (B) test item in 2 litres test medium. Hence, the theoretical CO2 production following complete degradation was 87.6 mg per 2 Iitres for A and 88.0 mg per 2 litres for B.
The positive control contained 80.0 mg sodium acetate (ThC02=1.07 mg CO2/mg) resulting in a theoretical CO2 production following complete degradation of 85.6 mg per 2 litres.
The toxicity control contained 80.0 mg sodium acetate and 42.1 mg test item in 2 Iitres of test medium. Hence, the theoretical CO2 production following complete degradation of test substance plus sodium acetate was 174.0 mg per 2 litres.
In the toxicity control more than 25 % degradation occurred within 14 days (39%, based on ThCO2). Therefore, the test substance was assumed to be not inhibitory to microbial activity.

Acceptability of the test:
The positive control substance was degraded at least 60% (73%) within 14 days.
The total CO2 release in the blank at the end of the test did not exceed 40 mg/L (47.2 mg CO2 per 2 Iitres of medium, corresponding with 23.6 mg CO2/L).
The difference of duplicate values for %-degradation of the test substance was always less than 20.
Since all criteria for acceptability of the test were met, this study was considered to be valid.

Results with reference substance:

The positive control substance was degraded at least 60% (73%) within 14 days.

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

Ethyltriphenylphosphonium iodide was not readily biodegradable under the conditions of the modified Sturm test.

Description of key information

Ethyltriphenylphosphonium iodide is not readily biodegradable under the conditions of the CO₂ Evolution Test (modified Sturm test, OECD 301B, GLP).

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

The biodegradation of Ethyltriphenylphosphonium iodide was investigated over a 29-day period in a CO₂ Evolution Test (modified Sturm test) according to OECD guideline 301 B (1992).

Ethyltriphenylphosphonium iodide is not readily biodegradable in this test.

Ethyltriphenylphosphonium iodide is not inhibitory to microorganisms at a concentration of 21 mg/L.