(2-hydroxyethyl)ammonium mercaptoacetate

Adsorption / desorption

Administrative data

Endpoint:

adsorption / desorption: screening

Type of information:

(Q)SAR

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model and falling into its applicability domain, with limited documentation / justification

Justification for type of information:

1. SOFTWARE
EpiSuite v4.11, US EPA, 2012

2. MODEL (incl. version number)
KOCWIN v2.00 (MCI method)

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
O=C(O)CS

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
- Defined endpoint: Koc
MCI (molecular connectivity index) method
The equation derived by the non-polar (no correction factor) regression is:
log Koc = 0.5213 MCI + 0.60
(n = 69, r2 = 0.967, std dev = 0.247, avg dev = 0.199)
for comparison, the previous version of PCKOCWIN used a very similar equation:
log Koc = 0.53 MCI + 0.62
Adding in the correction factor regression yields the final MCI equation:
log Koc = 0.5213 MCI + 0.60 + ΣPfN
where ΣPfN is the summation of the products of all applicable correction factor coefficients multiplied by the number of times (N) that factor is counted for the structure.

- Defined domain of applicability:
Currently there is no universally accepted definition of model domain. However, users may wish to
consider the possibility that log P estimates are less accurate for compounds outside the MW
range of the training set compounds, and/or that have more instances of a given fragment than the
maximum for all training set compounds. It is also possible that a compound may have a functional
group(s) or other structural features not represented in the training set, and for which no fragment
coefficient was developed. These points should be taken into consideration when interpreting
model results.

Training Set Molecular Weights:
Minimum MW: 32.04
Maximum MW: 665.02
Average MW: 224.4
Validation Molecular Weights:
Minimum MW: 73.14
Maximum MW: 504.12
Average MW: 277.8

- Appropriate measures of goodness-of-fit and robustness and predictivity:
Overall, the MCI methodology is somewhat more accurate than the Log Kow methodology, although both methods yield good results. If the Training datasets are combined in to one dataset of 516 compounds (69 having no corrections plus 447 with corrections), the MCI methodology has an r2, standard deviation and average deviation of 0.916, 0.330 and 0.263, respectively.

5. APPLICABILITY DOMAIN
- Descriptor domain: The components of the substance are within the molecular weight range of the training set compounds, and all fragments are represented in the training set. Thus, it is concluded, that the substance is within the applicability domain.
- Similarity with analogues in the training set: several linear and branched alkanes and alkenes, which are considered to be similar, are present in the training set.

6. ADEQUACY OF THE RESULT
The QSAR prediction is valid and of good reliability. Thus, the result is adequate for chemical safety assessment.

Data source

Reference

Reference Type:

other: QSAR

Title:

Adsorption estimations by KocWin 2.0

Author:

KocWin v2.0

Year:

2012

Bibliographic source:

Epiweb v4.11

Materials and methods

Principles of method if other than guideline:

(Q)SAR: QSAR linear regression analysis equations were developed utilizing Molecular Connectivity Index (MCI).

GLP compliance:

no

Remarks:

not applicable for in silico method

Type of method:

other: estimated by QSAR

Test material

Test material information

Constituent 1

Reference substance name:

(2-hydroxyethyl)ammonium mercaptoacetate

EC Number:

204-815-4

EC Name:

(2-hydroxyethyl)ammonium mercaptoacetate

Cas Number:

126-97-6

Molecular formula:

C2H7NO.C2H4O2S

IUPAC Name:

2-hydroxyethan-1-aminium 2-sulfanylacetate

Details on test material:

- Name of test material: Monoethanolamine Thioglycolate 83,7%
- Content of active ingredient: 83.7%
All test concentrations were corrected for active ingredient content.
- Lot/batch No.: 9787
- Physical state: colourless liquid
- Description: aqueous solution
- Storage condition of test material: room temperature in the dark, under nitrogen in a glass bottle

Study design

Test temperature:

n.a.

HPLC method

Details on study design: HPLC method:

n.a.

Batch equilibrium or other method

Analytical monitoring:

not required

Details on sampling:

n.a.

Details on matrix:

n.a.

Details on test conditions:

n.a.

Computational methods:

n.a.

Results and discussion

Adsorption coefficient

Key result

Type:

Koc

Value:

1.44 L/kg

Temp.:

25 °C

Remarks on result:

other: no data on pH; QSAR

Remarks:

QSAR

Results: HPLC method

Details on results (HPLC method):

n.a.

Results: Batch equilibrium or other method

Adsorption and desorption constants:

n.a.

Recovery of test material:

n.a.

Concentration of test substance at end of adsorption equilibration period:

n.a.

Concentration of test substance at end of desorption equilibration period:

n.a.

Transformation products:

not measured

Details on results (Batch equilibrium method):

n.a.

Statistics:

Koc was estimated with the Kocwin software v2.00 (MCI method). Thioglycolic acid is a small linear molecule with one terminal carboxilic group and one terminal mercaptan group. According to its descriptors, it falls in the scope of the MCI model, as indicated in appendix D of the KOCWIN v2.00 user manual.

Any other information on results incl. tables

SMILES : O=C(O)CS
MOL FOR: C2 H4 O2 S1
Koc may be sensitive to pH!
--------------------------- KOCWIN v2.00 Results ---------------------------

Koc Estimate from MCI:
---------------------
First Order Molecular Connectivity Index ........... : 2.270
Non-Corrected Log Koc (0.5213 MCI + 0.60) .......... : 1.7832
Fragment Correction(s):
* Organic Acid (-CO-OH) ............... : -1.6249
Corrected Log Koc .................................. : 0.1583

Estimated Koc: 1.44 L/kg <===========

Koc Estimate from Log Kow:
-------------------------
Log Kow (experimental DB) ......................... : 0.09
Non-Corrected Log Koc (0.55313 logKow + 0.9251) .... : 0.9749
Fragment Correction(s):
* Organic Acid (-CO-OH) ............... : -0.7694
Corrected Log Koc .................................. : 0.2055

Estimated Koc: 1.605 L/kg <===========

********************************************************************
* NOTE: *
* The Koc of this structure may be sensitive to pH! The estimated *
* Koc represents a best-fit to the majority of experimental values *
* however, the Koc may vary significantly with pH. *
********************************************************************

 

Applicant's summary and conclusion

Validity criteria fulfilled:

not applicable

Conclusions:

Log Koc was estimated by QSAR using the MCI method. Log Koc = 1.44

Executive summary:

Log Koc was estimated with KOCWIN v2.0 of the Episuite v4.11 software by QSAR using the MCI method. The descriptors of thioglycolic acid fall in the scope of the MCI model, as indicated in appendix D of the KOC user manual. Log Koc = 1.44