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Adsorption / desorption

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adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2001-03-22 to 2001-03-26
1 (reliable without restriction)
Cross-referenceopen allclose all
Reason / purpose for cross-reference:
reference to same study
Reason / purpose for cross-reference:
reference to other study

Data source

Reference Type:
study report
Report date:

Materials and methods

Test guideline
according to 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:
GLP compliance:
yes (incl. QA statement)
Type of method:
HPLC estimation method
soil/sewage sludge

Test material

Constituent 1
Chemical structure
Reference substance name:
Pentapotassium bis(peroxymonosulphate) bis(sulphate)
EC Number:
EC Name:
Pentapotassium bis(peroxymonosulphate) bis(sulphate)
Cas Number:
Molecular formula:
pentapotassium bis(peroxymonosulphate) bis(sulphate)
Details on test material:
- Physical state: white powder
- Lot/batch No.: H-24607
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):

Study design

Test temperature:

HPLC method

Details on study design: HPLC method:
Principle of the method
Chemicals injected onto a cyano column move along it by partitioning between the mobile phase and the stationary phase. The velocity of each component thereby depends on the degree of adsorption in the stationary phase. The dual nature of the moderately polar stationary phase, which contains lipophilic and polar moieties, allows for interaction of polar and apolar parts of a molecule in a similar way as in the case for soil. This enables the relationship between retention time on such a column and the adsorption coefficient on the organic parts of the soil to be established. The adsorption coefficient is deduced from the capacity factor (k) using a calibration plot of log k versus log Koc of the selected reference compounds. The capacity factor is calculated from the equation:
k = (tr-to)/to
to = column dead time (retention time of an inert substance)
tr = retention time of the test substance/reference compound

Measurement of dead time
The dead time (the average time a solvent molecule needs to pass through the column) was taken as the elution time of the thiourea, an organic compound for this purpose.

Preparation of the reference solutions
In order to correlate the measured capacity factor (k) of the test material with its Koc, six reference compounds are normally selected from the list of recommended compounds. However, in this particular case, preliminary results indicated that KMPS triple salt was not retained on the column. Therefore only two were selected in order to demonstrate that these were indeed retained.
Stock solutions of thiourea and of the reference compounds were prepared in methanol/water, 55/45 v/v. Individual solutions of thiourea and of each reference compound were then prepared by diluting the stock solutions with methanol/water, 55/45 v/v. The reference compound (and concentration) used were thiourea (5.54 mg/L), acetanilide (9.82 mg/L) and atrazine (3.17 mg/L). These solutions were analysed by HPLC to determine the individual retention times.

Preparation of test solution
KMPS triple salt (0.25048 g) was weighed into a 100 ml volumetric flask, and dissolved in and diluted to volume with water. An aliquot (9ml) was then pipetted into a 20 ml volumetric flask, and diluted to volume with methanol, in duplicate, to give solutions of concentration 1127.2 mg/L in methanol/water, 55/45 v/v. Injections (50 µl) were made onto the HPLC column from these solutions.
Methanol/water 55/45, v/v, was injected onto HPLC column, under the same conditions as the test solution, to act as blank solution.

HPLC conditions
HPLC system:
Autosampler: Moedl ISS200, Perkin Elmer
Detector: Model 481, Water Associates
Pump: Model 510, Water Associates
Data handling system: Turbochrom, PE Nelson
Column: Cyano Apex, 5 µm, 25 cm * 4.6 mm id.
Mobile phase: Methanol/water, 55/45, v/v
Flow rate: 1 ml/min
Comunm temperature: 20 °C
Injection volume: 50 µl
Detection: 210 nm

Batch equilibrium or other method

Analytical monitoring:
not specified
Details on sampling:
not indicated
Details on matrix:
not indicated
Details on test conditions:
not indicated
Computational methods:
not indicated

Results and discussion

Adsorption coefficientopen allclose all
< 18
log Koc
< 1.25

Results: HPLC method

Details on results (HPLC method):
The dead time (to), as determined from the retention time of thiourea, was 3.26 minutes. The retention time of acetanilide was 3.79 minutes (0.49 µg injected) and that of atrazine was 4.17 minutes (0.16 µg injected).
KMPS triple salt chromatographed as a single peak with retention times from the two injections of 2.15 and 2.16 minutes (the mass of the test substance introduced onto the column in each injection was 56 µg). Hence, log Koc will be quoted as being less than that of the fastest-eluting reference compound (acetanilide, which has a log Koc of 1.25 and a Koc of 18).
It was evident that thiourea was not a suitable compound for the assessment of the dead time of the column, as it eluted after the test substance. However, as the result from the test is being quoted as a limit value, it does not affect the validity of the conclusion drawn.
No peaks were seen in the blank solution chromatogram at the expected retention time of KMPS triple salt or at the characteristic retention times of two reference compounds.
There was no evidence of the column degradation in this study: reference compounds injected before and after the test substance produced peaks with no difference in retention time or peak shape.

Results: Batch equilibrium or other method

Adsorption and desorption constants:
not indicated
Recovery of test material:
not indicated
Concentration of test substance at end of adsorption equilibration period:
not indicated
Concentration of test substance at end of desorption equilibration period:
not indicated
Transformation products:
not specified
Details on results (Batch equilibrium method):
not indicated

Any other information on results incl. tables

no remarks

Applicant's summary and conclusion

Validity criteria fulfilled:
not specified
The soil adsorption coefficient of Oxone® Monopersulfate Compound has been determined as:
Koc < 18 at 20 °C
The result indicates that the test substance is likely to have very high mobility in soils.
Executive summary:

The study was performed to determine the soil adsorption coefficient (Koc) of Oxone® Monopersulfate Compound. The method followed was amongst those described in the OECD Guidelines for the testing of Chemicals. The result from the study is summarised below:

OECD-Method  Test  Result 
Draft Guideline 121  Soil adsorption coefficient  Koc < 18 at 20 °C 

The result indicates that the mobility of the test substance in soils is very high.

The result also indicates that the test substance is not likely to adsorp to sewage sludge in significant amounts.