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Endpoint:
adsorption / desorption: screening
Remarks:
adsorption
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
GLP study according to standard guideline.
Qualifier:
according to
Guideline:
other: Section G. 1.2 of the Dutch Pesticide Guideline
Deviations:
no
Principles of method if other than guideline:
The test guideline used is comparable to OECD guideline 106.
GLP compliance:
yes
Type of method:
HPLC estimation method
Media:
soil
Radiolabelling:
yes
Test temperature:
20 ± 2 °C
Details on study design: HPLC method:
HPLC system:
Column: Hypersil ODS 100 x 3 mm with a reversed phase guard column.
Mobile phase: methanol: ultrapure water (40:60), pH adjusted to 2.5 with phosphoric acid.
Flow: 0.8 mL/min, injection volume 100 μl
Details on test conditions:
TEST SOLUTIONS
A stock solution containing about 100 μg/mL of [14C]Chloramine-T trihydrate was prepared as follows: The stock solution of [14C]Chloramine-T trihydrate in ethanol contained about 35.6 MBq/mL. An aliquot of 40 μL was transferred to a vial and the ethanol was evaporated by a stream of air. The [14C]-labelled test substance was then dissolved in 16 mL 0.01 M CaS04 solution. The initial amounts of radioactivity per series were determined by pipetting duplicate aliquots of the solution into scintillation vials containing 5 mL scintillation fluid (Ultima Gold Canberra Packard).

TEST CONDITIONS
The test was carried out in 20 mL scintillation vials closed with screw caps. One gram dry weight of each soil sample was placed in an appropriate number of test vials together with a total volume of 10 mL liquid (0.01 M CaS04 solution and radiolabelled test solution). The reference vials were prepared without soil, and were treated in the same manner as the other vials. Appropriate amounts of the test substance stock solution were pipetted into duplicate test vials for each soil type to reach nominal final concentrations of 5, 10, 20 and 50 μg [14C]Chloramine-T trihydrate per vial. The test vials were shaken for about 18 hours in a temperature controlled room at 20 ± 2 °C in the dark. The vials were then centrifuged and duplicate samples of the supernatant (1 mL) were pipetted into vials containing 5 mL scintillation fluid and counted. From the results of the counts the Ceq (concentration of test substance in the solution (μg/mL) was calculated.
As the adsorption was found to be less than 10% the adsorption to the soil samples was estimated by extracting the samples with the highest concentration of [14C]Chloramine-T trihydrate (50 μg per vial) with a total amount of 10 mL of methanol by shaking the vials for about 2 hours. After centrifugation, one mL of the methanol of each extract was counted in duplicate.
Computational methods:
The adsorption constants were calculated according to the equation of Freundlich
(modified by Boesten [3])
Type:
other: Adsorption constants calculated on organic matter base (Kom)
Value:
31 L/kg
Temp.:
20 °C
Matrix:
sandy laom soil
Type:
other: Adsorption constants calculated on organic matter base (Kom)
Value:
52 L/kg
Temp.:
20 °C
Matrix:
loam soil
Type:
other: Adsorption constants calculated on organic matter base (Kom)
Value:
43 L/kg
Temp.:
20 °C
Matrix:
Low humic content sand soil
Concentration of test substance at end of desorption equilibration period:
No desorption was determined
Transformation products:
yes
No.:
#1
Statistics:
Regression analyses

The adsorption constant values based on total soil were: (1 microgram/ml) 
0.68 ml/g sandy laom soil
1.04 ml/g loam soil
0.43 ml/g low humic content soil  
Adsorption constants calculated on organic matter (Kom) were 31, 52 and 43 ml/g respectively for these soils. These
values indicates that Halamid is only very slightly adsorbed
to soil particles.

Percentage adsorption of [14C]Halamid to soil after 18 hours of shaking at 20 °C in the dark. Adsorption was calculated using the concentration of [14C]Halamid found in the reference vials.

Amount of [14C]Halamid

Sandy loam soil

Low humic content sand soil

Loam soil

Nominal conc. µg/10 ml

Found conc. µg/10 ml

Ads* (%)

Ads* (%)

Ads* (%)

5

4.89

8.8

3.4

11.8

10

10.12

6.5

5.8

9.2

20

19.64

3.9

3.6

7.8

50

48.31

5.3

3.8

7.4

Extract**

10.5

7.4

12.9

* calculated by dividing the amount of test substance adsorbed by the amount of [14C]Halamid found

** percentage of test substance found in the methanol extract of the soil samples

Calculated values for the distribution coeffiecient K, the adsorption coefficient based on organic matter Kom, the Freundlich exponent 1/N and the correlation coefficient for the adsorption isotherm r for [14C]Chloramine-T trihydrate at the reference concentration 1 μg/mL.

Soil

K (mL/g)

Kom (mL/g)

1/N

r

Sandy loam soil

0.68

31

0.723

0.945

Loam soil

1.04

52

0.777

0.995

Low humic content sand soil

0.43

43

0.976

0.976

Validity criteria fulfilled:
yes
Conclusions:
The adsorption constants were found to be low, indicating that [14C]Tosylchloramide sodium, trihydrate is only very slightly adsorbed to soil particles.
A complicating factor is that the [14C]Tosylchloramide sodium, trihydrate preparation contains a considerable amount of its hydrolysis product p-toluenesulfonamide (p-tsa). Furthermore, results of a soil biodegradation test indicate that [14C]Halamid will disappear rapidly in the soil leaving the slower degrading p-tsa. The results therefore indicate that also this hydrolysis product of [14C]Tosylchloramide sodium, trihydrate is only very slightly adsorbed to soil particles.
Executive summary:

The adsorption of [14C] Tosylchloramide sodium, trihydrate to soil particles was determined according to the Dutch Board for the Authorization of Pesticides Guidelines section G. 1.2, the OECD Guideline no. 106, and in compliance with the OECD Principles of Good Laboratory Practice (GLP). The adsorption of test substance has been determined by the slurry method with three soil types (i.e. sandy loam, loam and low humic content sand soil) known to have a pH value between 6 and 8.5. Adsorption constant values based on total soil, were 0.68 mL/g for sandy loam soil, 1.04 mL/g for loam soil and 0.43 mL/g for low humic content sand soil at the reference solution concentration of 1 µg/mL. Adsorption constants calculated on organic carbon base (Koc,) were 31, 52 and 43 mL/g respectively for these soils. These low adsorption coefficients indicate that the test substance is only very slightly adsorbed to soil particles. Due to the instability of the substance in water and soil it is assumed that also its hydrolysis product p-toluenesulfonamide is only very slightly adsorbed to soil particles.

Endpoint:
adsorption / desorption
Remarks:
adsorption
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
4 (not assignable)
Rationale for reliability incl. deficiencies:
other: No standard method used, not enough details on test method and test conditions.
Qualifier:
according to
Guideline:
other: protocols set up by the Dutch Commission for the Authorization of Herbicides (CTB)
Principles of method if other than guideline:
An adsorption test was carried out in which use was made of one type of synthetic soil and one type of activated sludge. Since the decomposition of Chloramine-T trihydrate into PTSA and possible other waste products might have an adverse effect on the analysis, and hence on the measurement of the adsorption behavior, it was decided to measure by means of DOC (= Dissolved Organic Carbon) determination.
The determination was carried out as follows:
10 g of dry soil or 100 mL of sludge having a solids content of 2.3 g / L was introduced into 100 mL of a Chloramine-T trihydrate solution in distilled water. After shaking for 20 hours and 30 min., respectively, the suspension was centrifuged. Samples of the clear supernatant were analyzed using a Dohrmann TC 80 TOC analyzer.
GLP compliance:
no
Remarks:
test was conducted pre-GLP
Type of method:
other: DOC determination in time
Media:
soil
Radiolabelling:
no
Analytical monitoring:
no
Value:
< 500 other: mg/kg
Matrix:
Organic matter in soil or sludge
Remarks on result:
other: Less than 500 mg of Chloramine-T trihydrate is adsorbed per kg of organic matter in soil or sludge.

The theoretical DOC value for the test substance is 0.298 mg
C/l. A solution of 1 g/l test substance gave DOC-values of
resp. 276 and 293 for soil and sludge. Recovery of the
analytical method therefore is resp. 93 and 98%. Measured
versus theoretical DOC values indicate that an insignificant
amount of test material is adsorbed to soil or sludge (<500
mg/kg).  For this reason no further than one type of soil
was studied.

DOC values found testing halamid adsorption by soil

Nominal halamid conc. (mg/l)

Measured DOC

DOC minus control

Nominal DOC x recovery (=93%)

Control

0.9-1.1

-

-

10

3.7

2.8

2.8

32

9.2

8.3

8.8

100

28.6

27.7

27.7

320

91.5

90.6

88.7

1000

287

286

277

DOC values found testing halamid adsorption by activated sludge

Nominal halamid conc. (mg/l)

Measured DOC

DOC minus control

Nominal DOC x recovery (=93%)

Control

6.1-6.4

-

-

10

8.6

2.5

2.9

32

15.1

8.9

9.4

100

31.2

25.0

29.2

320

97.5

91.1

93.6

1000

288.5

282.3

292.0

Validity criteria fulfilled:
no
Conclusions:
Given the accuracy of this measuring technique (5%), it is safe to conclude that no significant adsorption has occurred. Less than 500 mg of Chloramine-T trihydrate is adsorbed per kg of organic matter in soil or sludge.

Description of key information

The adsorption of [14C] Tosylchloramide sodium, trihydrate to soil particles was determined according to the Dutch Board for the Authorization of Pesticides Guidelines section G. 1.2, the OECD Guideline no. 106, and in compliance with the OECD Principles of Good Laboratory Practice (GLP). The adsorption of test substance has been determined by the slurry method with three soil types (i.e. sandy loam, loam and low humic content sand soil) known to have a pH value between 6 and 8.5. Adsorption constant values based on total soil, were 0.68 mL/g for sandy loam soil, 1.04 mL/g for loam soil and 0.43 mL/g for low humic content sand soil at the reference solution concentration of 1 µg/mL. Adsorption constants calculated on organic carbon base (Koc,) were 31, 52 and 43 mL/g respectively for these soils. These low adsorption coefficients indicate that the test substance is only very slightly adsorbed to soil particles. Due to the instability of the substance in water and soil it is assumed that also its hydrolysis product p-toluenesulfonamide is only very slightly adsorbed to soil particles.

Key value for chemical safety assessment

Koc at 20 °C:
52

Additional information

The test substance is immediately transformed into p-TSA when it is brought into contact with soil. The distribution parameters presented therefore refer to the degradation product p-TSA. Based on the log Kow of both the parent compound and the degradation product, the sorption of the parent compound will be lower or comparable.