Results - Biodegradability - STABILGREEN® K

PERFORMANCE OF THE STUDY

Preparations

The medium was prepared from the stock solutions. The inoculum was taken from its source, washed, aerated and the dry matter was determined.

The test vessels were filled with medium and inoculum. Then all flasks were aerated for 72 hours with purified, CO2-free, moistened air to purge the system of CO2.

Experimental Parameters

Flask volume	1500 mL
Apparatus blanks	2, containing mineral medium only
Controls	2, containing mineral medium and inoculum
Positive control flasks	2, containing positive control, mineral medium and inoculum
Test flasks	2, containing test substance, mineral medium and inoculum
Abiotic control	1, containing test substance, mineral medium and HgCl2
Toxicity control	1, containing test substance, positive control, mineral medium and inoculum
Inoculum concentration	25.0 mg/L
Temperature	19.2 – 21.4°C
Duration	28 days

The test was performed with a nominal start concentration of 20 mg organic carbon/L. The following amounts of test substance and positive control were added to the flasks:

Table Amounts of test substance and positive control in the flasks

Flask	Positive Control 1	Positive Control 2	Test 1	Test 2	Abiotic Control	Toxicity Control
Amount STABILGREEN®K (Polyglyceryl-4 Oleyl Ether, Dioleyl Phosphate)in mg / L	—	—	28.1	27.5	27.7	28.0
Amount Aniline in mg / L	24.5	24.5	—	—	—	24.5
organic C (calculated) in mg / L	20.0	20.0	20.3	19.9	20.1	40.2

Apparatus

The test vessels were aerated with purified (by activated charcoal), CO2-scrubbed, moistened air. The scrubbing of carbon dioxide was achieved by bubbling the purified air through a flask containing 1.5 m-NaOH. To control the absence of CO2, the air was then led through a flask containing a solution of Ba(OH)2 before reaching the test vessels.
Magnetic stirrers were used to prevent deposition of inoculum.

The emitted CO2 was trapped in 0.25-m-NaOH. Two scrubbers containing 100 mL each were connected in series to the test vessels. The initial IC value of the 0.25 m-NaOH was separately determined in each flask.

Sampling

From each front scrubber flask, ten samples were taken in order to determine the emitted CO2. (on days 0, 2, 4, 7, 9, 11, 14, 18, 23 and 29). The sample volume was 1 mL. The resulting change in the volume of the front flask was considered in the calculation of emitted CO2.

On day 28, 5 mL HCl 2-m. were added to each test flask in order to drive off dissolved CO2. On day 29, samples from both scrubber flasks were taken.

CO2 Determination

Analyses of the emitted CO2 were made by IC measurement using the carbon analyser TOC multi N/C 2100S, Analytik Jena. Each sample was measured at least in duplicate. The carbon analyser was calibrated with freshly prepared reference solutions containing potassium hydrogen phthalate and sodium carbonate once a week. After every start, quality control samples were measured.

FINDINGS

Tables

IC-Values

In the following tables, the IC values (given in mg/L) which were measured in the samples of the front scrubber flasks are stated.

Table IC Values in mg/L Apparatus Blanks, Controls, front scrubber

Day	Apparatus blank 1	Apparatus blank 2	Control 1	Control 2
0	0.74	1.20	1.28	1.80
2	2.70	4.08	10.24	9.09
4	4.14	5.18	21.03	17.16
7	4.69	6.07	35.74	29.69
9	5.79	7.64	42.17	37.43
11	6.33	8.34	43.62	41.19
14	7.24	11.36	51.94	50.40
18	10.24	13.27	59.40	57.75
23	12.48	17.61	65.40	66.07
29	16.60	22.49	75.91	76.79

Table IC Values in mg/L Positive Control, Test Flasks, front scrubber

Day	Positive Control 1	Positive Control 2	Test 1	Test 2	Abiotic Control	Toxicity Control
0	1.42	1.00	0.63	0.35	0.55	1.86
2	7.51	11.91	23.60	18.76	5.20	43.74
4	55.54	109.72	88.12	58.05	5.38	303.68
7	193.95	251.25	187.58	162.56	6.97	448.58
9	264.64	278.75	204.48	210.59	8.09	493.20
11	270.29	282.51	227.77	234.35	8.05	504.15
14	289.95	288.15	259.95	261.16	10.01	519.19
18	318.81	322.09	281.70	277.74	12.01	516.20
23	335.71	338.78	301.60	291.50	13.31	551.95
29	347.17	353.45	334.16	332.07	16.02	583.85

In the following tables, the IC values which were measured in the samples of the back scrubber flasks are stated.

Table IC Values in mg/L Controls, Apparatus Blanks, back scrubber

Day	Apparatus blank 1	Apparatus blank 2	Control 1	Control 2
0	0.86	1.88	0.72	1.29
29	10.06	12.28	3.22	4.31

Table 3.1-d IC Values in mg/L Positive Control, Test Flasks, back scrubber

Day	Positive Control 1	Positive Control 2	Test 1	Test 2	Abiotic Control	Toxicity Control
0	1.19	0.73	1.08	1.67	0.64	2.20
29	5.29	3.20	4.16	6.57	21.56	10.96

Net IC

For each flask, the IC value which was measured at the start of the test (d = 0) was subtracted from all following measurements. The net IC was calculated using this corrected measurement value and subtracting the mean IC value of the apparatus blanks of that sampling date.
The net IC values are presented in the following table.

Table Net IC-values in mg/L front scrubber flasks

Day	Control 1	Control 2	Positive Control 1	Positive Control 2	Test 1	Test 2	Abiotic Control	Toxicity Control
0	1.3	1.8	1.4	1.0	0.6	0.3	0.6	1.9
2	7.8	6.7	5.1	9.5	21.2	16.3	2.8	41.3
4	17.3	13.5	51.9	106.0	84.4	54.4	1.7	300.0
7	31.3	25.3	189.5	246.8	183.2	158.2	2.6	444.2
9	36.4	31.7	258.9	273.0	198.7	204.8	2.3	487.5
11	37.3	34.8	263.9	276.1	221.4	228.0	1.7	497.8
14	43.6	42.1	281.6	279.8	251.6	252.8	1.7	510.9
18	48.6	47.0	308.0	311.3	270.9	267.0	1.2	505.4
23	51.3	52.0	321.6	324.7	287.5	277.4	-0.8	537.9
29	57.3	58.2	328.6	334.9	315.6	313.5	-2.6	565.3

Table Net IC-values in mg/L back scrubber flasks

Day	Control 1	Control 2	Positive Control 1	Positive Control 2	Test 1	Test 2	Abiotic Control	Toxicity Control
0	0.7	1.3	1.2	0.7	1.1	1.7	0.6	2.2
29	-6.6	-5.5	-4.5	-6.6	-5.6	-3.2	11.8	1.2

Negative values occur, when the apparatus blank was higher than the respective treatment. As the measured values in these blanks as well as in the abiotic control are very low, measurement uncertainties lead to negative degradation values in the abiotic control.

pH

In the following table, the pH at the end of the test (before addition of HCl) is given:

Table pH Test flasks on day 28

Day	Control 1	Control 2	Positive Control 1	Positive Control 2	Test 1	Test 2	Abiotic Control	Toxicity Control
28	7.4	7.4	7.2	7.2	7.4	7.3	6.8	7.2

Equations

Emitted Carbon in mg/L

Emitted Carbon in mg/L test solution at time t is calculated using the following equation:

with:

emittC: emitted carbon in mg/L test solution
IC(t): inorganic carbon in mg/L NaOH at time t
IC(0): inorganic carbon in mg/L NaOH at the start of the test
VolNaOH (t): remaining volume NaOH in L in the scrubber at time t (Volume at t = 0 (here: 0.1 L) – Ʃ (all sample volumes up to time t))
VolTestVessel: test vessel volume in L (here: 1.5)

For day 29, the IC content of both scrubber flasks was taken into account.

Calculation of emitted carbon is necessary for the assessment of validity. The value obtained with this equation is multiplied with 3.667 (44/12) in order to obtain emitted CO2.

Degradation in %

The percentage biodegradation in the test flasks was calculated from:

Degradation in positive control and toxicity flasks was calculated analogously.

Calculation Results

Emitted Carbon in mg/L

In the following table, the calculated emitted carbon (from IC values given in 3.1 and equation stated in 3.2.1) is presented.

Table Emitted carbon in mg/L

Day	Control 1	Control 2	Positive Control 1	Positive Control 2	Test 1	Test 2	Abiotic Control	Toxicity Control
2	0.43	0.32	0.24	0.56	1.36	1.06	0.15	2.60
4	1.05	0.76	3.29	6.86	5.47	3.53	0.07	19.48
7	1.94	1.52	12.17	15.90	11.80	10.20	0.13	28.60
9	2.25	1.91	16.48	17.41	12.68	13.09	0.11	31.08
11	2.28	2.09	16.63	17.43	13.98	14.42	0.07	31.41
14	2.65	2.52	17.56	17.47	15.73	15.82	0.07	31.90
18	2.93	2.80	19.01	19.24	16.76	16.53	0.04	31.22
23	3.07	3.08	19.64	19.85	17.60	16.99	-0.08	32.88
29	2.92	2.98	19.47	19.77	18.66	18.67	0.55	34.11

Degradation Values

In the following table the percentage biodegradation is presented:

Table Degradation values in %

Day	Positive Control 1	Positive Control 2	Positive Control Mean	Test 1	Test 2	Test Mean	Abiotic Control	Toxicity Control
2	-0.7	0.9	0.1	4.8	3.4	4.1	0.7	5.5
4	12.0	29.9	20.9	22.5	13.2	17.9	0.4	46.2
7	52.3	71.0	61.7	49.6	42.7	46.2	0.6	66.9
9	72.2	76.8	74.5	52.2	55.4	53.8	0.6	72.1
11	72.4	76.4	74.4	58.1	61.6	59.9	0.4	72.7
14	75.0	74.6	74.8	64.8	66.6	65.7	0.4	72.9
18	80.9	82.1	81.5	68.4	68.8	68.6	0.2	70.5
23	83.0	84.1	83.6	71.6	70.1	70.8	-0.4	74.1
29	82.8	84.3	83.6	77.5	79.2	78.3	2.7	77.5

Degradation Graph

RESULTS AND VALIDITY
Results for the Test substance

Time in Days

The test substance STABILGREEN®K (Polyglyceryl-4 Oleyl Ether, Dioleyl Phosphate) is considered as “readily biodegradable“.
Ready biodegradability is defined in the guidelines as degradation surpassing 60% within 10 days after reaching a level of 10%. The 10-day-window began on day 3, at its end, 64 % were reached, surpassing the pass level of 60 % given in the OECD guideline.
The degree of biodegradation reached 78% after 28 days.
The abiotic degradation reached 2.7 %.

Validity

All validity parameters and values are presented in the following table:

Table Validity

Parameter	Criterion	Found	Assessment
IC content of test substance solution in medium	≤ 5% of TC	0.60 %	valid
CO2 emitted by the controls	< 70 mg/L	10.8 mg/L	valid
Difference within replicates	≤ 20%	1.7 %	valid
Degradation of positive control > 60%	< 14 days	7 days	valid
Degradation in the toxicity flask on day 14	> 25%	73%	valid

Materials & methods Results Download

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Results – Biodegradability – STABILGREEN® K

PERFORMANCE OF THE STUDY

Preparations

Experimental Parameters

Apparatus

Sampling

CO2 Determination

FINDINGS

Tables

IC-Values

Net IC

pH

Equations

Emitted Carbon in mg/L

Degradation in %

Calculation Results

Emitted Carbon in mg/L

Degradation Values

Degradation Graph

RESULTS AND VALIDITY
Results for the Test substance

Validity

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Results – Biodegradability – STABILGREEN® K

PERFORMANCE OF THE STUDY

Preparations

Experimental Parameters

Apparatus

Sampling

CO2 Determination

FINDINGS

Tables

IC-Values

Net IC

pH

Equations

Emitted Carbon in mg/L

Degradation in %

Calculation Results

Emitted Carbon in mg/L

Degradation Values

Degradation Graph

RESULTS AND VALIDITYResults for the Test substance

Validity

RESULTS AND VALIDITY
Results for the Test substance