3-[[3-(dimethylamino)propyl]amino]propiononitrile

Adsorption / desorption

Link to relevant study record(s)

Reference

Endpoint:

adsorption / desorption: screening

Type of information:

other: No determination of the adsorption coefficient was possible by, Method C19 Adsorption Coefficient of Commission Regulation (EC) No 440/2008 of 30 May 2008 and Method 121 of the OECD Guidelines for Testing of Chemicals, 22 January 2001.

Remarks:

The method was invalid for the test item. The method is not valid for organic bases.

Adequacy of study:

weight of evidence

Study period:

This study was conducted between 09 April 2016 and 16 December 2016

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

unsuitable test system

Justification for type of information:

No determination of the adsorption coefficient was possible by the HPLC estimation method, Method C19 Adsorption Coefficient of Commission Regulation (EC) No 440/2008 of 30 May 2008 and Method 121 of the OECD Guidelines for Testing of Chemicals, 22 January 2001. This was since the method was invalid for the test item. The method is not valid for organic bases.

Qualifier:

according to guideline

Guideline:

OECD Guideline 121 (Estimation of the Adsorption Coefficient (Koc) on Soil and on Sewage Sludge using High Performance Liquid Chromatography (HPLC))

Version / remarks:

22 January 20001

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.19 (Estimation of the Adsorption Coefficient (KOC) on Soil and Sewage Sludge Using High Performance Liquid Chromatography (HPLC))

Version / remarks:

30 May 2008

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of method:

other:

Media:

other: Not applicable

Radiolabelling:

no

Key result

Remarks on result:

not determinable because of methodological limitations

Remarks:

Method not applicable to organic bases

Validity criteria fulfilled:

not applicable

Conclusions:

From available literature values and experimental experience, the test item was predicted to have a very high affinity for soils, possibly an apparent log10 Koc >5.

Executive summary:

Adsorption Coefficient. No determination was possible according to Method C.19 Adsorption Coefficient of Commission Regulation (EC) No 440/2008 of 30 May 2008 and Method 121 of the OECD Guidelines for Testing of Chemicals, 22 January 2001, due to the  reasons given below:

No determination of the adsorption coefficient was possible by the HPLC estimation method, Method C19 Adsorption Coefficient of Commission Regulation (EC) No 440/2008 of 30 May 2008 and Method 121 of the OECD Guidelines for Testing of Chemicals, 22 January 2001.  This was since the method was invalid for the test item. The method is not valid for organic bases.  The dissociation constant of the two primary amine functional groups was predicted to be 7.3 and 9.6 respectively (Advance Chemistry Development, Inc., ACD/pKa version 8.03).  Therefore the test item would maintain at least a single cationic charge over the entire environmentally relevant pH range of 5.5 to 7.5 applicable for the method. Cationic species have been demonstrated to interact with the HPLC column stationary phase by mechanisms other than partitioning, thus invalidating the estimation of the adsorption coefficient of the test item by comparison to the capacity factors of reference substances of known adsorption coefficient values.

For the test item, a unionised form will exist only at a pH of approximately 5 to 7 and therefore is not relevant to environmental assessment when addressing the adsorption coefficient.  With respect to possible experimental analysis of the remaining ionised form found at an approximately neutral pH, experience supports the method guideline caution of validity for this chemical class.  The HPLC column stationary phase required by the guidelines is that of cyanopropyl groups established on a silica backbone.  Critically however, this silica backbone contains a number of free silanol groups (Si-OH) which present an anionic charge at a neutral mobile phase pH as required by the method.  This presents a significant opportunity for retention of a cationic substance by secondary ionic interactions, as opposed to partitioning onto the cyanopropyl groups as intended by the method.

This has been demonstrated internally by the analysis of cationic substances under neutral and acidic conditions.  Under neutral conditions the silanol groups are ionised and under acidic conditions the silanol groups revert to a unionised form.  Both the stationary phase as defined by the OECD guideline and the ionised state of the cationic molecule remains the same under both sets of conditions yet a significance difference in the retention time of the analyte is observed based on whether the secondary ionic interactions from the silanol groups is activated or not. This indicates a very significant influence of these free silanol groups on the final estimated adsorption coefficient value. Although there is the option of performing the analysis at an acidic pH to eliminate the silanol interaction, this is not performed due to possible conflict on submission of the data, as it would be generated outside of the environmentally relevant pH range.

Overall the actual concept of an organic carbon normalised adsorption coefficient for a cationic molecule is limited as the organic carbon content of a soil or sludge may not be the critical factor for the mobility of the substance, hence the absence of correlation between partition coefficient and apparent adsorption coefficient for this chemical class.  

No alternative estimation method was available for the determination of the adsorption coefficient of this test item.  However, an example of a cationic structure available from literature was that of paraquat dichloride, which has a distribution coefficient (Kd) greater than 1 x 104 (Tomlin CDS (editor) The Pesticide Manual, 2000, British Crop Protection Council, Surrey).  With soils typically containing significantly less than 10% organic carbon, the resulting apparent value of log10 Koc would be greater than 5. Also from experimental experience of studying quaternary amine containing compounds in soil/water systems using OECD Method 106, this cationic chemical class typically shows a very high affinity for soils.

Therefore in conclusion, from available literature values and experimental experience, the test item was predicted to have a very high affinity for soils, possibly an apparent log10 Koc >5.

Description of key information

No determination of the adsorption coefficient was possible by the HPLC estimation method, Method C19 Adsorption Coefficient of Commission Regulation (EC) No 440/2008 of 30 May 2008 and Method 121 of the OECD Guidelines for Testing of Chemicals, 22 January 2001.  This was since the method was invalid for the test item. The method is not valid for organic bases.  The dissociation constant of the two primary amine functional groups was predicted to be 7.3 and 9.6 respectively (Advance Chemistry Development, Inc., ACD/pKa version 8.03).  Therefore the test item would maintain at least a single cationic charge over the entire environmentally relevant pH range of 5.5 to 7.5 applicable for the method. Cationic species have been demonstrated to interact with the HPLC column stationary phase by mechanisms other than partitioning, thus invalidating the estimation of the adsorption coefficient of the test item by comparison to the capacity factors of reference substances of known adsorption coefficient values.

Key value for chemical safety assessment

Koc at 20 °C:

100 000

Additional information

[LogKoc: 5.0]