Ammonium sulphamidate

Adsorption / desorption

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

key study

Study period:

24 May 2011 and 08 November 2011

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Study conducted in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results. The study report was conclusive, done to a valid guideline and the study was conducted under GLP conditions.

Qualifier:

equivalent or similar to guideline

Guideline:

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

Deviations:

no

Qualifier:

equivalent or similar to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of method:

HPLC estimation method

Media:

other: Not applicable.

Radiolabelling:

no

Test temperature:

30ºC

Details on study design: HPLC method:

Preparation of sample solution:
Test item (2.0233 g) was diluted to 100 ml with mobile phase.

Preparation of reference solutions:
The dead time was determined by measuring the retention time of formamide (purity 99.94%, 626 mg/l solution in mobile phase).

Solutions of reference standards (see table 1) were prepared in methanol.

Determination of retention time:
The sample, dead time and reference standard solutions were injected in duplicate using the following HPLC parameters:
HPLC System : Agilent Technologies 1200, incorporating workstation
Column : Optimal CN 5 µm (150 x 4.6 mm id)
Column temperature : 30ºC
Mobile phase : methanol : reverse osmosis water (55:45 v/v)
Flow-rate : 1.0 ml/min
Injection volume: 10 µl
Detectors :
Standards and dead time: UV: 210 nm
Samples: Refractive index: positive polarity
Temperature: 35°C


Construction of calibration curve:
A calibration curve was constructed from the retention time data of the dead time and reference standard solutions. The capacity factors (k) for the reference standards were calculated using Equation 1 (see below)

Adsorption coefficient of sample:
The capacity factor was calculated using Equation 2 (see below) and the log10 Koc value determined with reference to the calibration curve.

Analytical monitoring:

no

Type:

Koc

Value:

< 17.8

Temp.:

30 °C

Type:

log Koc

Value:

< 1.25

Temp.:

30 °C

Details on results (HPLC method):

See any other information on results incl. tables section.

Transformation products:

not measured

Details on results (Batch equilibrium method):

Not applicable.

Statistics:

None stated.

Calibration

The retention times of formamide and the retention times, capacity factors (k) and log₁₀K_oc values for the reference standards are shown in the two following tables:

Dead Time (UV detector)	Retention Time (mins)		Mean Retention Time (mins)
	Injection 1	Injection 2
Formamide	2.021	2.012	2.017

Standard	Retention Time (mins)		Mean Retention Time (mins)	Capacity Factor (k)	Log10k	Log10Koc
	Injection 1	Injection 2
Acetanilide	2.629	2.629	2.629	0.304	-0.517	1.25
Phenol	2.677	2.677	2.677	0.328	-0.485	1.32
Atrazine	3.086	3.090	3.088	0.531	-0.275	1.81
Isoproturon	3.401	3.401	3.401	0.687	-0.163	1.86
Triadimenol	4.140	4.140	4.140	1.05	2.24 x 10^-2	2.40
Linuron	4.854	4.849	4.852	1.42	0.148	2.59
Naphthalene	4.495	4.495	4.495	1.23	8.96 x 10^-2	2.75
Endosulfan-diol	6.113	6.103	6.108	2.03	0.307	3.02
Fenthion	7.575	7.585	7.580	2.76	0.441	3.31
a-Endosulfan	8.834	8.829	8.832	3.38	0.529	4.09
Phenanthrene	7.643	7.643	7.643	2.79	0.446	4.09
Diclofop-methyl	8.878	8.882	8.880	3.40	0.532	4.20
DDT	17.692	17.711	17.702	7.78	0.891	5.63

 

Adsorption coefficient of sample

The retention times, capacity factors and log₁₀K_oc values determined for the sample are shown in the following table:

Injection	Retention Time (mins)	Capacity Factor (k)	Log10k	Log10Koc
1	2.030	6.67 x 10^-3	<-0.517	<1.25
2	2.038	1.07 x 10^-2	<-0.517	<1.25

Mean log₁₀K_oc:                    <1.25
Adsorption coefficient:       <17.8

Validity criteria fulfilled:

yes

Conclusions:

The adsorption coefficient (Koc) of the test item has been determined to be less than 17.8 (log10 Koc <1.25).

Executive summary:

Adsorption Coefficient Less than 17.8 (log₁₀K_oc <1.25) using the HPLC screening method, designed to be compatible with 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.

Reference 2

Endpoint:

adsorption / desorption: screening

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Remarks:

sodium sulphamidate

Adequacy of study:

weight of evidence

Justification for type of information:

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
A read across, based on analogue approach, has been performed between ammonium sulphamidate EC 231-871-7 (target chemical) and sodium sulphamidate EC 237-572-8 (source chemical).
The read-across hypothesis, according to Read Across Assessment Framework published by ECHA, is based on the fact that different compounds which have the same type of effect(s). It corresponds to the scenario 2 described as follows:
« This scenario covers the analogue approach for which the read-across hypothesis is based on different compounds which have the same type of effect(s). For the REACH information requirement under consideration, the effects obtained in a study conducted with one source substance are used to predict the effects that would be observed in a study with the target substance if it were to be conducted. The same type of effect(s) or absence of effect is predicted. The predicted strength of the effects may be similar or based on a worst case assumption. »

1) Chemical structure
The target and source substances share the same anionic structure, i.e. a sulphamidate (formula: –OSO2NH2). They only differ by the positive counter ion: an ammonium ion (NH4+) for the target substance and a sodium ion (Na+) for the source substance. It is well known that usually, the counter ion has no impact on the toxicity profile of the substance. For this reason, the QSARs are classically performed on the “core” of the salt and do not consider the counter ion.
See the structures in attached justification.

2) Kinetics
Ammonium sulphamidate
The substance is highly water soluble, meaning its ions dissolve in water. Following oral administration of ammonium sulfamate to dogs for 5 days, 80 to 84% of the dose was excreted as sulfamic acid in the urine, indicating that ammonium sulfamate is readily absorbed into the bloodstream from the gastrointestinal tract. (Pesticide Active Ingredient Information – EXTOXNET)

Sodium sulphamidate
Absorption of sodium sulphamidate from the gastrointestinal tract is supported by the repeated dose reproductive screening study in rats. The high water solubility and small molecular size of sodium sulphamidate allow absorption through passive diffusion. This would suggest that the gastro-intestinal tract provides a route of absorption, following oral administration, before entering the circulatory system via the blood.
Absorption of sodium sulphamidate may also take place via the skin due to small molecular size and water solubility. Although the substance is not a skin sensitizer there is evidence of mild dermal irritation. Therefore damage to the skin surface may allow for increased penetration of the substance through the skin.

Once absorbed, the substance would be distributed in the serum due to the water solubility.

The results of the repeated dose reproductive screening study would suggest that the most likely route of excretion is the kidney due to the likely systemic distribution and water solubility of the test item. Any test item that is not absorbed will be excreted in the faeces. [ECHA’s registration dossier of sodium sulphamidate].

Conclusion
Both substances are absorbed via oral route and are found excreted in urine. Inhalation exposure is not relevant due to the low vapour pressure of each substance.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
1) Physical and chemical information
The physico-chemical properties were compared between the target and the source substance. Synthron data are in blue and Nalco data (found in ECHA’s registration dossier of sodium sulphamidate) are in green. Published data are in purple and other data are in black (please refer to the comparative table in attached justification).

Both substances share some common physico-chemical properties: white solid appearance, decomposition, high partition coefficient, negligible vapour pressure, absence of surface activity, good water solubility, absence of flammability/explosive and oxidizing properties.
Some physico-chemical differences can be highlighted between the two substances: the different molecular weight is attributed to the counter-ion. The boiling and melting points are slightly different as well as the relative density. The dissociation constants vary due to the different counter-ions which cannot be used for the read-across proposal. In this case, the sulphamidic acid is the most appropriate substance. The pKa values around 1.0 (0.9 or 0.997 or 1.05 as found in the "Handbook of Chemistry and Physics", 85th ed.) all refer to the free acid, sulphamidic acid. Ammonium sulphamate contains as cation the ammonium ion with a pKa of 9.25 ("Handbook of Chemistry and Physics", 85th ed.) Any attempt of coming into the region of pH that is near the pKa of the primary amine group (13.6 ± 0.6) would cause the deprotonation of the ammonium ion and the transformation of the target chemical into the respective alkaline metal salt, for instance sodium sulphamidate. Therefore, the pKa of the primary amine group in the sulphamidate anion reported in the sodium sulphamidate dossier is not relevant for ammonium sulphamidate.
Therefore, both substances share many common physico-chemical features, and the observed differences can be attributed to the different counter-ion.

2) Toxicological and ecotoxicological information
The ammonium ion of the target substance may contribute to the toxicity of ammonium sulphamidate, compared to sodium sulphamidate. However, as both substances are highly water soluble, their ions dissolve in water. Therefore, the ammonium ion is no more a concern.
Please refer to the comparative table in attached justification.

Regarding the toxicity endpoints, some common points are shared by the two substances: low acute toxicity by oral route, no mutagenicity in bacteria, mild to no skin or eye irritation. Some differences occurred in the systemic toxicity study: in the repeated dose toxicity study, the NOAEL are not the same between sodium (NOAEL = 1000 mg/kg bw/d) and ammonium sulphamidate (NOEL = 214.3 mg/kg bw/d). In the reproductive study, NOEL for ammonium sulphamidate was found to be 25 mg/kg bw/d in the literature whereas the NOAEL for sodium sulphamidate is 1000 mg/kg bw/d. However, these differences must be considered with caution as the experimental protocols differ.

As for the ecotoxicity endpoints, both substances seem not to be toxic to fish, based on their LC50 > 100 mg/L (LC50 of at least 650 mg/L).

Last, the environmental fate data on both substances indicate that they are likely to be adsorbed into the soil. Their half-life differ as sodium sulphamidate is very stable (half-life > 1 year) and ammonium sulphamidate may be less stable (half-life of 14 days, based on a published data).


3) Classification proposal
The sodium sulphamidate is not classified in ECHA’s registration dossier. Based on the read-across approach, ammonium sulphamidate would not be classified either.

3. ANALOGUE APPROACH JUSTIFICATION
Based on the available elements, it can be assumed that ammonium and sodium sulphamidate may have close kinetic profiles, physico-chemical, toxicological and ecotoxicological properties. The read-across approach is therefore relevant.

Reason / purpose for cross-reference:

read-across source

Type:

Koc

Value:

< 17.8 L/kg

Temp.:

30 °C

Type:

log Koc

Value:

< 1.25 dimensionless

Temp.:

30 °C

Validity criteria fulfilled:

yes

Conclusions:

Based on the read-across on sodium sulphamidate, ammonium sulphamidate is expected to have a log10 Koc lower than 1.25.

Key value for chemical safety assessment

Koc at 20 °C:

17.8