Mercaptoacetic acid

Additional information on environmental fate and behaviour

Administrative data

Endpoint:

additional information on environmental fate and behaviour

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

August 02 to August 05 2009

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Non GLP guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2009

Report date:

2009

Materials and methods

Test guideline

Guideline:

other:

Principles of method if other than guideline:

A concentration of appr. 100 ppm of test material in water was prepared. Concentration of thioglycolic acid (TGA) and dithiodiglycolic acid (DTDGA) at the beginning of test was determined by HPLC. The solution is aerated before and during the test with an aquarium pump connected to a glass tube with frit feeding air into the solution to maintain saturated concentration of oxygen in the solution. Samples of the aerated solution were taken every hour and measured immediately by HPLC. pH value at several stages of study was measured. Study was conducted at room temperature of 22 to 24°C.

GLP compliance:

no

Remarks:

This study was not performed under GLP conditions. The central laboratory was quality audited regarding ISO 9001:2000 by TÜV-Cert in June 2007, surveyance audit May 2009.

Test material

Test material information

Constituent 1

Reference substance name:

Mercaptoacetic acid

EC Number:

200-677-4

EC Name:

Mercaptoacetic acid

Cas Number:

68-11-1

Molecular formula:

C2H4O2S

IUPAC Name:

2-sulfanylacetic acid

Details on test material:

Test Mat.: thioglycolic acid (TGA),
Appearance: Clear colorless liquid
Content %w/w: 99.4 iodometric
Test material provider: Bruno Bock
Lot no.: Insp. Lot 790000007112

Results and discussion

Any other information on results incl. tables

The test was carried out as described.

The pH value of the tapwater was 7.66 before introducing the test material.

Change of pH-value with oxidation in shown together with the measured concentrations in the following table.

Time (h)	TGA (ppm)	DTDGA (ppm)	Ox Prod (% w/w)	pH	Temp (°C)	Peak at 6.032 min (area %)
0	0	0	0	7.66	23.2
0	101*	0	0	6.64	22.2
0	92	9	8.9	6.64	22.2	0.5
0.5	48	32	31.7	8.08	22.5	18.3
1	0	71	70.3	8.08	22.7	22.1
1.5	0	71	70.3	8.09	22.9	21.3
2	0	72	71.3	8.13	23.2	20.8
23	0	71	70.3			11.7

* nominal concentration

Applicant's summary and conclusion

Executive summary:

In aerated tap water - which is comparable to ground water and surface water - the oxidation of the test material was completed after 1.5 hours with the theoretical amount of 71.3 % of oxidation product detected. The first step of oxidation took place during the preparation of the sample at start point. After one hour ongoing oxidation another unidentified product evolved at later retention time than DTDGA. The pH value rose with ongoing oxidation. The unidentified peak is very broad, this is a hint to an alkaline substance. The area of this peak also decreases after 23 hours to a value of 60% of its maximum.

The velocity of degradation of thioglycolic acid in oxygen saturated tap water was such high, that the first sample taken at start point showed already considerable amount of oxidation product. During degradation an unidentified peak appeared, but the amount measured in area% decreased in 22 hours to 60 % of the maximum initial value of this peak after one hour degradation time.