Summary of OECD 111 Tier 1 Testing: 

Hydrolysis of ALFOTERRA® Surfactants as a 

Function of pH

RESEARCH REPORT

Greg Trahan, Charles Hammond, 

Mark Bose, and Todd Houser

Research Report: R&D ANL 10-004 01-10

July 13, 2010

Sasol North America Incorporated

Research and Development

Lake Charles, LA 70669
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Test Substances

The following materials were tested for hydrolytic stability under OECD 111: OECD 

Guidelines for the Testing of Chemicals: Hydrolysis as a Function of pH. These alcohol 

propoxy sulfates are manufactured to have an active component of 30 ± 5%. This 

translates to the product sold containing 25 - 35% alcohol propoxy sulfate. Additionally, 

there is up to 10% unsulfated starting material, the propoxy alcohol. The target value for 

unsulfated propoxy alcohol is <5%. The balance of 55 - 65% is water.

Table I. Sasol Italy Substances Tested Under Tier I Guidelines of OECD 111

Trade Name Common Name Chemical Name

CAS 

Number

Carbon 

chain 

Length

PO 

Units

(n)

ALFOTERRA® 

123-4S 

C12C13 

branched 

propoxy sulfate, 

sodium salt

Poly[oxy(methyl-1,2-

ethanediyl)], α-sulfo-ωhydroxy-, C12-13-branched 

and linear alkyl ethers, 

sodium salts 958238-81-8 12-13 4

ALFOTERRA® 

123-8S

C12C13 

branched 

propoxy sulfate, 

sodium salt

Poly[oxy(methyl-1,2-

ethanediyl)], α-sulfo-ωhydroxy-, C12-13-branched 

and linear alkyl ethers, 

sodium salts 958238-81-8 12-13 8

ALFOTERRA® 

145-4S

C14C15 

branched 

propoxy sulfate, 

sodium salt

Poly[oxy(methyl-1,2-

ethanediyl)], α-sulfo-ωhydroxy-, C14-15-branched 

and linear alkyl ethers, 

sodium salts 958238-82-9 14-15 4

ALFOTERRA® 

145-8S

C14C15 

branched 

propoxy sulfate, 

sodium salt

Poly[oxy(methyl-1,2-

ethanediyl)], α-sulfo-ωhydroxy-, C14-15-branched 

and linear alkyl ethers, 

sodium salts 958238-82-9 14-15 8

ALFOTERRA® 

L167-4S

C16C17 

branched and 

linear propoxy 

sulfate, sodium 

salt

Poly[oxy(methyl-1,2-

ethanediyl)], α-sulfo-ωhydroxy-, C16-17-branched 

and linear alkyl ethers, 

sodium salts 958238-83-0 16-17 4

C16C17 branched 

and linear propoxy 

sulfate, sodium salt

Poly[oxy(methyl-1,2-

ethanediyl)], α-sulfo-ωhydroxy-, C16-17-branched 

and linear alkyl ethers, 

sodium salts 958238-83-0 16-17 7
3

Figure 1. Structure of ALFOTERRA® Substances Studied

Buffer Solutions

For Tier I testing, buffers were prepared on 6-22-10 according to “Annex 3” of OECD 

111. Each pH buffer prepared was tested with a calibrated pH meter, and the actual pH 

values for the buffers were found to be 4.0, 7.0, and 9.0 as intended. For details on the 

preparation of buffer solutions, refer to the procedure followed in Appendix I.

Test Conditions

The tests performed in the Tier 1 hydrolysis study were done in two separate batches of 

single replicate runs. ALFOTERRA® 123-4S and ALFOTERRA® 123-8S solutions 

were incubated for five days from 6/23/10 to 6/28/10. ALFOTERRA® 145-4S, 

ALFOTERRA® 145-8S, ALFOTERRA® L167-4S, and ALFOTERRA® L167-7S 

solutions were incubated for five days from 7/1/10 to 7/6/10. Test solutions in 1 oz. vials 

were incubated in the dark, in a forced air oven, which held an internal temperature of 

50°C. 100 mL samples were prepared for each test material at each pH required yielding 

buffered solutions with active concentrations between 0.25 and 0.35%. Two 1 oz vials 

were filled with approximately 30mL of each solution to make duplicate samples. One of 

the duplicates was incubated for five days and then analyzed, while the other duplicate 

was analyzed immediately to obtain a time “0” analysis. Further details of the 

experimental method can be found in Appendix I of this report.

Table II. Amount of Test Substance diluted in Buffer Solutions

Test Material

Mass diluted to 

100mL with pH 4 

buffer (g)

Mass diluted to 

100mL with pH 7 

buffer (g)

Mass diluted to 

100mL with pH 9 

buffer (g)

ALFOTERRA® 

123-4S 0.7434 0.7660 0.7332

ALFOTERRA® 

123-8S 1.1844 1.1722 1.1633

ALFOTERRA® 

145-4S 0.7342 0.7398 0.7483

C12 to C17 Carbon Chain Length

2-4 carbon branching

n = 4 – 8
4

ALFOTERRA® 

145-8S 1.1196 1.1075 1.1019

ALFOTERRA® 

L167-4S 0.8947 0.9236 0.9051

ALFOTERRA® 

L167-7S 1.1305 1.1457 1.1224

Results

ASTM D3049, Synthetic Anionic Ingredient by Cationic Titration, was the analysis used 

to quantify the amount of material in each test sample. Sasol control charts show the 

repeatability of this test to have a standard deviation of 0.16% when expressed as % 

active anionic surfactant. 

The amount of hydrolysis that occurred was determined on a molar basis by comparing 

the meq/100mL of the time “0” sample to the that of the time “5 day” sample. The 

following equation gives the % reduction of active surfactant test material after 

incubation for 5 days at 50°C.

 “meq/100mL of time 0”- “meq/100mL of time 5 days”

% reduction = ----------------------------------------------------------------- x 100%

“meq/100mL of time 0”

Table III. Reduction of Test Materials after 5 days at 50°C in pH 4 buffer

Test Material

Time "0" Analysis 

(meq active/100 mL)

Time "5 Day" Analysis 

(meq active/100 mL) % reduction

ALFOTERRA® 

123-4S 0.4560 0.4373 4.10

ALFOTERRA® 

123-8S 0.4670 0.4502 3.60

ALFOTERRA® 

145-4S 0.4401 0.4248 3.48

ALFOTERRA® 

145-8S 0.4578 0.4285 6.40

ALFOTERRA® 

L167-4S 0.4679 0.4437 5.17

ALFOTERRA® 

L167-7S 0.4682 0.4489 4.12

Table IV. Reduction of Test Materials after 5 days at 50°C in pH 7 buffer

Test Material

Time "0" Analysis 

(meq active/100 mL)

Time "5 Day" Analysis 

(meq active/100 mL) % reduction

ALFOTERRA® 

123-4S 0.4660 0.4581 1.70

ALFOTERRA® 

123-8S 0.4550 0.4373 3.90

ALFOTERRA® 

145-4S 0.4428 0.4358 1.58

ALFOTERRA® 

145-8S 0.4505 0.4269 5.24

ALFOTERRA® 

L167-4S 0.4767 0.4758 0.19
5

ALFOTERRA® 

L167-7S 0.4767 0.4599 3.52

Table V. Reduction of Test Materials after 5 days at 50°C in pH 9 buffer

Test Material

Time "0" Analysis 

(meq active/100 mL)

Time "5 Day" Analysis 

(meq active/100 mL) % reduction

ALFOTERRA® 

123-4S 0.4239 0.4074 3.90

ALFOTERRA® 

123-8S 0.4563 0.4428 3.00

ALFOTERRA® 

145-4S 0.4529 0.4517 0.26

ALFOTERRA® 

145-8S 0.4462 0.4395 1.50

ALFOTERRA® 

L167-4S 0.4703 0.4642 1.30

ALFOTERRA® 

L167-7S 0.4694 0.4673 0.45

According to the above data and OECD 111, the six materials tested above are 

considered to be hydrolytically stable since in all cases less than 10% hydrolysis was 

observed after 5 days of incubation at 50°C. No additional testing was performed under 

OECD 111 Tier 2 or Tier 3 guidelines. 
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Appendix I

Sasol Procedure Followed to determine Hydrolysis as a Function of pH: 

OECD 111 Tier I Testing

(Derived from OECD 111 Guidelines for the Testing of Chemicals: 

Hydrolysis as a Function of pH)

1. Properly clean glassware

a. Wash volumetric flasks and other glassware in a laboratory glassware 

washer with deionized water prior to use.

b. Rinse new 1 oz. vials for hydrolysis study three times with 18 MOhm 

NANOpure water, and dry in a vacuum oven overnight at 100°C.

2. Calculate the amount of test material to be used in the hydrolysis study.

a. Solutions are to be made in 100mL volumetric flasks.

b. ASTM D3049, Synthetic Anionic Ingredient by Cationic Titrations, will 

be used to characterize samples.

c. Ideally, a 10mL aliquot of sample will be used to analyze via ASTM 

D3049, thus the amount of test material to be added to each 100mL 

volumetric can be calculated by “grams of sample = (0.045 x eq wt of 

active)/(% active)”.

3. Prepare pH 4.0, 7.0, and 9.0 buffers according to “Annex 3” of OECD 111:

OECD Guidelines for the Testing of Chemicals: Hydrolysis as a Function of pH.

a. Prepare pH 4.0 buffer by combining 4.0mL of 0.1N NaOH and 500mL of 

0.1M potassium biphthalate in a 1000mL volumetric flask. Dilute to 

volume with 18 MOhm NANOpure water and mix by inverting several 

times.

b. Prepare pH 7.0 buffer by combining 296.3mL of 0.1N NaOH and 500mL 

of 0.1M monopotassium phosphate in a 1000mL volumetric flask. Dilute 

to volume with 18 MOhm NANOpure water and mix by inverting several 

times.

c. Prepare pH 9.0 buffer by combining 213.0mL of 0.1N NaOH and 500mL 

of 0.1M boric acid in 0.1M KCl in a 1000mL volumetric flask. Dilute to 

volume with 18 MOhm NANOpure water and mix by inverting several 

times.

4. Test each pH buffer.

a. Calibrate a pH meter with purchased pH 4, 7, and 9 standards.

b. Check each buffer with the calibrated pH meter to ensure it is +/- 0.1 units 

within the desired pH.

c. Remake any pH buffers that do not fall with the +/- 0.1 range of the target 

pH. 

5. Sparge each pH buffer with argon for five minutes. 
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Note: The remaining steps should be repeated

for each individual material being tested.

6. Purge and fill glassware with argon. 

a. Three 100mL volumetric flasks are required for each product tested. 

Purge and fill each with argon.

b. Six 1 oz. vials are required for each product being tested. Purge and fill 

each with argon. 

7. Charge each 100mL volumetric flask the appropriate amount of material being 

tested. 

a. Shake or mix the surfactant well before use.

b. Weigh the appropriate amount of surfactant into three volumetric flasks 

using an analytical balance. 

c. Record the weight. 

8. Dilute the three 100mL volumetric flasks.

a. Dilute the three 100mL volumetric flasks to volume with pH 4.0, 7.0, and 

9.0 buffers. 

b. Invert the flasks several times to thoroughly mix. 

9. Dispense the solutions to 1 oz. vials for testing.

a. Fill two 1 oz. vials to the neck (~30 mL per vial) with the contents of each 

100mL volumetric flask. There will be six 1 oz. vials; a duplicate for each 

pH.

b. Fill the headspace of the filled 1 oz. vials with argon.

c. The remainder of the contents of the 100mL volumetric flask can be 

retained or discarded.

10. Begin the hydrolysis study.

a. Place one of each pair of 1 oz vials in a equilibrated oven at 50°C. 

b. Submit the duplicate samples to the Analytical Services Department 

immediately for a time “0” analysis by ASTM D3049.

i. If samples can not be analyzed immediately, place them in a 

refrigerator for storage.

ii. Samples must be at room temperature before performing ASTM 

D3049 because sampling will be done by volume.

11. Allow the vials to remain in the oven for 5 days.

12. After 5 days, remove the vials from the oven and submit to the Analytical services 

Department immediately for the final time “5 day” analysis by ASTM D3049.

13. Compare time “0” and time “5 days” results to ascertain the amount of each 

sample that was hydrolyzed.
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a. If more than 10% of hydrolysis is observed after 5 days for any of the 

three pHs, proceed with Tier 2 testing.