Metam-sodium

Adsorption / desorption

Link to relevant study record(s)

Reference

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

secondary literature

Justification for type of information:

Data is from secondary source and authoritative database

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))

Principles of method if other than guideline:

Soil adsorption study was conducted for determining the adsorption coefficient (Koc) of test chemical Metam-sodium. The study was performed according to OECD Guideline 121 (Estimation of the Adsorption Coefficient (Koc) on Soil and on Sewage Sludge using High Performance Liquid Chromatography (HPLC)).

GLP compliance:

not specified

Type of method:

HPLC estimation method

Media:

soil

Specific details on test material used for the study:

- Name of test material (IUPAC name): Metam-sodium
- Common name: Sodium methyldithiocarbamate
- Molecular formula: C2H5NNaS2
- Molecular weight: 129.1826 g/mol
- Smiles notation: C(=S)(NC)[S-].[Na+]
- InChl: 1S/C2H5NS2.Na/c1-3-2(4)5;/h1H3,(H2,3,4,5);/q;+1/p-1
- Substance type: Organic
- Physical state: Solid
- Purity: 99.2%
- Batch: NV799R
- Other: Test chemical Metam-sodium was not radiolabelled during the study.

Radiolabelling:

not specified

Details on study design: HPLC method:

HPLC procedure
Metam-sodium was introduced onto a HPLC column in a 10 μl injection containing 507.90 ng (test 1, pH 4), 508.80 ng (test 2, pH4), 501.55 ng (test 1, pH 9) and 530.30 ng (test 2, pH 9). The capacity factor (k) was determined based on the retention time of Metam-sodium and sodium nitrate (inert substance). In order to correlate k with its Koc, six reference compounds (acetanilide, atrazine, triadimenol, naphthalene, pyrazophos and DDT) with log Koc values between 1.25 and 5.63 were selected and injected.

Analytical monitoring:

not specified

Key result

Type:

Koc

Value:

< 17.8 dimensionless

Remarks on result:

other: Log Koc= < 1.25, at pH 4 and 9

Transformation products:

not specified

Details on results (Batch equilibrium method):

Metam-sodium was eluted from the column more quickly than acetanilide (the reference standard with the lowest iterature value for log Koc). Therefore, the Adsorption coefficient (KOC) on soil of the substance Metam-sodium (CAS No. 137-42-8) was determined to be < 17.8 at 25°C.
The result indicates that the test substance is likely to have very high mobility in soils.
The pH’s of 4 and 9 were chosen as the two limits of pH likely to be found in the environment as this material is known to have a dissociation constant. However in each case the material was found to be very mobile in soil. An intermediate value of pH (neutral) would not be expected to give another result for the Koc if the two extremes give the same result.
The values from the dissociation constant study support these findings (values were 2.99 and 11.06) and hence no change would be expected over the range pH 4 to 9.

Validity criteria fulfilled:

not specified

Conclusions:

The Adsorption Coefficient of test substance Metam-sodium (CAS No. 137-42-8) was determined as per the HPLC method (OECD Guideline-121). The Log Koc value was determined to be < 1.25at pH 4 and 9, respectively.

Executive summary:

The adsorption coefficient Koc in soil of test chemical Metam-sodium (CAS No. 137-42-8) was determined by the Reverse Phase High Performance Liquid Chromatographic method according to OECD Guideline No. 121 for testing of Chemicals.Metam-sodium was introduced onto a HPLC column in a 10 μl injection containing 507.90 ng (test 1, pH 4), 508.80 ng (test 2, pH4), 501.55 ng (test 1, pH 9) and 530.30 ng (test 2, pH 9). The capacity factor (k) was determined based on the retention time of Metam-sodium and sodium nitrate (inert substance). In order to correlate k with its Koc, six reference compounds (acetanilide, atrazine, triadimenol, naphthalene, pyrazophos and DDT) with log Koc values between 1.25 and 5.63 were selected and injected. Metam-sodium was eluted from the column more quickly than acetanilide (the reference standard with the lowest iterature value for log Koc).The Log Koc value of the test chemical Metam-sodium was determined to be < 1.25 at pH 4 and 9, respectively. This log Koc value indicates that the substance Metam-sodium has a negligible sorption tosoil and sediment and therefore have rapid migration potential to ground water.

Description of key information

The adsorption coefficient Koc in soil of test chemical Metam-sodium (CAS No. 137-42-8) was determined by the Reverse Phase High Performance Liquid Chromatographic method according to OECD Guideline No. 121 for testing of Chemicals (from secondary source (Draft Assessment Report, 2007) and authoritative database (AGRITOX - Plant Protection Phentopharmaceuticals Database, 2012)). Metam-sodium was introduced onto a HPLC column in a 10 μl injection containing 507.90 ng (test 1, pH 4), 508.80 ng (test 2, pH4), 501.55 ng (test 1, pH 9) and 530.30 ng (test 2, pH 9). The capacity factor (k) was determined based on the retention time of Metam-sodium and sodium nitrate (inert substance). In order to correlate k with its Koc, six reference compounds (acetanilide, atrazine, triadimenol, naphthalene, pyrazophos and DDT) with log Koc values between 1.25 and 5.63 were selected and injected. Metam-sodium was eluted from the column more quickly than acetanilide (the reference standard with the lowest iterature value for log Koc).The Log Koc value of the test chemical Metam-sodium was determined to be < 1.25 at pH 4 and 9, respectively. This log Koc value indicates that the substance Metam-sodium has a negligible sorption tosoil and sediment and therefore have rapid migration potential to ground water.

Key value for chemical safety assessment

Koc at 20 °C:

0.096

Additional information

Experimental study and various predicted data for the target compound Metam-sodium (CAS No. 137-42-8) and various supporting weight of evidence studies for its structurally and functionally similar read across substance were reviewed for the adsorption end point which are summarized as below:

 

In an experimental weight of evidence study from secondary source (Draft Assessment Report, 2007) and authoritative database (AGRITOX - Plant Protection Phentopharmaceuticals Database, 2012), adsorption coefficient Koc in soil of test chemical Metam-sodium (CAS No. 137-42-8) was determined by the Reverse Phase High Performance Liquid Chromatographic method according to OECD Guideline No. 121 for testing of Chemicals.Metam-sodium was introduced onto a HPLC column in a 10 μl injection containing 507.90 ng (test 1, pH 4), 508.80 ng (test 2, pH4), 501.55 ng (test 1, pH 9) and 530.30 ng (test 2, pH 9). The capacity factor (k) was determined based on the retention time of Metam-sodium and sodium nitrate (inert substance). In order to correlate k with its Koc, six reference compounds (acetanilide, atrazine, triadimenol, naphthalene, pyrazophos and DDT) with log Koc values between 1.25 and 5.63 were selected and injected. Metam-sodium was eluted from the column more quickly than acetanilide (the reference standard with the lowest iterature value for log Koc).The Log Koc value of the test chemical Metam-sodium was determined to be < 1.25 at pH 4 and 9, respectively.

 

Another adsorption study was conducted for estimating the adsorption coefficient (Koc) value of test chemical Metam-sodium (CAS no. 137-42-8) (Pesticide Properties Database, 2017). The adsorption coefficient (Koc) value of substance Metam-sodium was estimated to be 10 (Log Koc = 1), respectively.

 

In a supporting weight of evidence study from authoritative database (Pesticide Properties Database, 2017) for the test chemical Metam-sodium (CAS no. 137-42-8),adsorption study was conducted for estimating the adsorption coefficient (Koc) value of test chemical Metam-sodium (CAS no. 137-42-8). The adsorption coefficient (Koc) value of substance Metam-sodium was estimated to be 17.8 (Log Koc = 1.25), respectively.

 

From CompTox Chemistry Dashboard using OPERA (OPEn (quantitative) structure-activity Relationship Application)  V1.02 model in which calculation based on PaDEL descriptors (calculate molecular descriptors and fingerprints of chemical), the adsorption coefficient i.e KOC for test substance Metam-sodium was estimated to be 13.4 L/kg (log Koc = 1.127).The predicted KOC result based on the 5 OECD principles.

 

In a supporting weight of evidence study from authoritative database (HSDB, 2017) for the read across chemical Disodium cyanodithiocarbamate (CAS no. 138-93-2),asorption experiment was conducted for estimating the adsorption coefficient (Koc) value of read across chemical Disodium cyanodithiocarbamate (CAS no. 138-93-2). The adsorption coefficient (Koc) value was calculated using a structure estimation method based on molecular connectivity indices. The adsorption coefficient (Koc) value of test substance Disodium cyanodithiocarbamate was estimated to be 2 (Log Koc = 0.3).

 

For the read across chemical Sodium dimethyldithiocarbamate (CAS no. 128-04-1),adsorption study was conducted for estimating the adsorption coefficient (Koc) value of read across chemical Sodium dimethyldithiocarbamate (CAS no. 128-04-1). The adsorption coefficient (Koc) value was calculated using a water solubility of 1000000 mg/l and a regression derived equation. The adsorption coefficient (Koc) value of test substance Sodium dimethyldithiocarbamate was estimated to be 2.2 (Log Koc = 0.342).

 

On the basis of above overall results for target chemical Metam-sodium (from secondary source, authoritative database AGRITOX - Plant Protection Phentopharmaceuticals Database and Pesticide Properties Database &CompTox Chemistry Dashboard,2017) and for its read across substance (from authoritative database HSDB, 2017), it can be concluded that the log Koc value of test substance Metam-sodiumranges from 1–1.25 indicating that the test chemical Metam-sodium has a negligible sorption to soil and sediment and therefore have rapid migration potential to ground water.

 

[LogKoc: 1.25]