Benzimidazole

Adsorption / desorption

Link to relevant study record(s)

Reference

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

Experimental result using OECD guidelines.

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:

To determine Adsorption coefficient (KOC) on soil and on sewage sludge of the Benzimidazole (CAS No. 51-17-2) using HPLC.

GLP compliance:

no

Type of method:

HPLC estimation method

Media:

soil/sewage sludge

Specific details on test material used for the study:

- IUPAC name: 1H-benzimidazole
- Name of test material (as cited in study report):Benzimidazole
- Molecular formula: C7H6N2
- Molecular weight: 118.1384 g/mol
- Substance type: Organic
- Physical state: Solid

SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material:L146211607
- Expiration date of the lot/batch:2021-06-01


STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material:Ambient Temp (23 to 27 °C) (Store in a cool, dry, well ventilated place. Keep away from sources of heat & ignition. Store away from incompatible compounds, such as oxidizing agents, acids)
- Stability under test conditions:Stable in recommended storage conditions

Radiolabelling:

not specified

Test temperature:

25°C

Details on study design: HPLC method:

The solutions of the test substance and reference substances were prepared in the mobile phase. Each of the reference substance and test substance were analysed by HPLC at 210 nm.
After equilibration of the HPLC system, Urea was injected first, the reference substances were injected in duplicate, followed by the test chemical solution in duplicate. Reference substances were injected again after test sample, no change in retention time of reference substances was observed.
Retention time tR were measured, averaged and the decimal logarithms of the capacity factors k were calculated. The graph was plotted between log Koc versus log k(Annex - 2).The linear regression parameter of the relationship log Koc vs log k were also calculated from the data obtained with calibration samples and therewith, log Koc of the test substance was determined from its measured capacity factor.

Operating Conditions:
HPLC Model No. : Agilent Technologies,1260 Infinity
Flow Rate : 1.0 mL/min
Column : ZORBAX Eclipse Plus C18, 4.6×100mm, 3.5 μm
Mobile phase : Acetonitrile: water (55:45)
Temperature : 25°C
Detector : Diode Array Detector @210nm
Injector : Autosampler
Injector volume : 10μl
Data Acquisition software : ChemStationOpen lab Control Panel

Details on test conditions:

A test item solution was prepared by accurately weighing 5 mg of test item and diluted with mobile phase up (Acetonitrile: water- 55:45, %v/v) to 10 ml. Thus, the test solution concentration was 500 mg/l. The pH of test substance was 7.65.

Key result

Type:

log Koc

Value:

1.687 dimensionless

pH:

7.65

Temp.:

25 °C

Remarks on result:

other: reported as 1.6871± 0.0

Transformation products:

not specified

Table 1

Reference substance	Log Koc	Rt1	Rt2	Rt3	Mean Rt ± S.D.	k	Log k
Urea		0.887	0.887	0.888	0.887±0.0005	0	0
4-chloroaniline	1.96	2.012	2.021		2.0165±0.0063	1.2734	0.105
4-methylaniline(p-Tolouidine)	1.9	1.755	1.748		1.7515±0.0049	0.9746	-0.0112
N-methylaniline	2.28	2.303	2.294		2.2985±0.0063	1.5913	0.2018
p-toluamide	1.78	1.18	1.182		1.181±0.0014	0.3315	-0.4796
Aniline	2.07	1.513	1.495		1.504±0.0127	0.6956	-0.1576
2,5-Dichloroaniline	2.58	3.548	3.574		3.561±0.0183	3.0147	0.4792
4-nitrophenol	2.46	1.559	1.56		1.5595±0.0007	0.7582	-0.1202
2-nitrophenol	2.47	2.213	2.224		2.2185±0.0077	1.5011	0.1764
2-nitrobenzamide	1.45	1.091	1.094		1.0925±0.0021	0.2317	-0.6351
3-nitrobenzamide	1.95	1.159	1.158		1.1585±0.0007	0.3061	-0.5142
Nitrobenzene	2.35	2.426	2.429		2.4275±0.0021	1.7368	0.2397
4-Nitrobenzamide	1.93	1.161	1.159		1.16±0.0014	0.3078	-0.5118
1-naphthylamine	3.51	2.389	2.393		2.391±0.0028	1.6956	0.2293
1-naphtol	3.3	2.41	2.403		2.4065±0.0049	1.7131	0.2338
DirectRed81	3.43	0.827	0.818		0.8225±0.0063	-0.0727	1.139
Benzoicacidmethylester	1.8	2.585	2.61		2.5975±0.0176	0.1917	-0.7175
Carbendazim	2.35	1.193	1.193		1.193±0	0.345	-0.4622
Benzoicacidphenylester	2.87	6.57	6.642		2.5975±0.0509	1.9284	0.2852
Xylene	2.58	6.241	6.232		6.2365±0.0063	6.031	0.7804
Ethylbenzene	2.649	6.359	6.355		6.357±0.0028	6.1669	0.7901
Toluene	2.369	4.378	4.382		4.38±0.0028	3.938	0.5953
Naphthalene	2.75	6.127	6.218		6.1725±0.0643	5.9589	0.7752
1,2,3-trichlorobenzene	3.16	9.519	9.541		9.53±0.0155	9.7441	0.9887
Pentachlorophenol	3.695	8.282	8.259		8.2705±0.0162	8.3241	0.9203
Phenol	1.32	1.455	1.455		1.455±0	0.6404	-0.1936
N,N-dimethylbenzamide	1.52	1.287	1.288		1.2875±0.0007	0.4515	-0.3453
3,5-dinitrobenzamide	2.31	1.308	1.311		1.3095±0.0021	0.4763	-0.3221
N-methylbenzamide	1.3	1.175	1.174		1.1745±0.0007	0.3241	-0.4893
Benzamide	1.26	1.092	1.092		1.092±0	0.2311	-0.6362
phenanthrene	4.09	11.996	11.779		11.8875±0.1534	12.4019	1.0935
Acetanilide	1.25	1.265	1.267		1.266±0.0014	0.4273	-0.3693

Test substance Benzimidazole		K	Log k	Log Koc by Generalized Calibration Graph	Mean of Log Koc ± S.D.
tR1	1.159	0.3066	-0.5133	1.6871	1.6871± 0.0
tR2	1.159	0.3066	-0.5133	1.6871

Validity criteria fulfilled:

yes

Conclusions:

The Adsorption Coefficient of test substance Benzimidazole (CAS No. 51-17-2)was determined as per the HPLC method (OECD Guideline-121). The Log Koc value was determined to be 1.6871± 0.0 at 25°C.

Executive summary:

The adsorption coefficient Koc in soil and in sewage sludge Benzimidazole (CAS No.51-17-2) was determined by the Reverse Phase High Performance Liquid Chromatography method according to OECD Guideline No. 121 for testing of Chemicals. The reference substances were chosen according to estimated Koc range of the test substance and generalized calibration graph was prepared. The reference substances were having Koc value ranging from 1.25 to 4.09. The Log Koc value was found to be 1.6871± 0.0 at 25°C.

 

Thus based on the result it is concluded that the test substance Benzimidazole (CAS No.51-17-2) has a low sorption to soil and sediment and therefore has moderate migration potential to ground water.

Description of key information

The adsorption coefficient Koc in soil and in sewage sludge Benzimidazole (CAS No.51-17-2) was determined by the Reverse Phase High Performance Liquid Chromatography method according to OECD Guideline No. 121 for testing of Chemicals. The reference substances were chosen according to estimated Koc range of the test substance and generalized calibration graph was prepared. The reference substances were having Koc value ranging from 1.25 to 4.09. The Log Koc value was determined to be 1.6871± 0.0 at 25°C.

Thus based on the result it is concluded that the test substance Benzimidazole (CAS No.51-17-2) has a low sorption to soil and sediment and therefore has moderate migration potential to ground water

Key value for chemical safety assessment

Koc at 20 °C:

48.7

Additional information

Four different studies which includes three experimental reports from and remaining one from validated predicted model for adsorption endpoint for target chemical 1H-benzimidazole or benzimidazole (CAs no. 51-17-2) are summarized as followed:

 

Experimental key study for adsorption was performed in this study the adsorption coefficient Koc in soil and in sewage sludge Benzimidazole(CAS No.51-17-2) was determined by the Reverse Phase High Performance Liquid Chromatography method according to OECD Guideline No. 121 for testing of Chemicals. The reference substances were chosen according to estimated Koc range of the test substance and generalized calibration graph was prepared. The reference substances were having Koc value ranging from 1.25 to 4.09. The Log Koc value was determined to be 1.6871± 0.0 at 25°C.

Thus based on the result it is concluded that the test substance Benzimidazole (CAS No.51-17-2) has a low sorption to soil and sediment and therefore has moderate migration potential to ground water

Above result supported by one another experimental study for target which indicate the effect of pH on the adsorption by montmorillonite and kaolinite clays of three benzimidazole derivatives, thiabendazole (TBZ), 2-benzimidazole carbamic acid methyl ester (MBC), and benzimidazole, was investigated.

Montmorillonite No. 25 API, Project No. 49 (bentonite), was from Upton Wyoming, and a commercial supply of bentonite was obtained from Upton Wyoming. During this study no real differences were found between the two sources of bentonite and montmorillonite. Ca- and Na-montmorillonite were prepared from Wyoming bentonite according to the procedure described by Shainberg . Kaolinite, Peerless clay No. 2, was from South Carolina.

Adsorption as a function of pH was determined by stirring a clay fungicide suspension of 450 ml with an ionic strength of 0.01MCaC12, the pH being changed by the addition of either HCl or NaOH. The suspension was progressively sampled, after 3 hr of equilibration, duplicate suspension samples of 10 ml each were withdrawn and centrifuged, and the supernatant was taken for analysis. The pH was changed every 30 min by 0.5 pH unit. At the end of each 30-min period, duplicate samples were withdrawn.The solution reached equilibrium within these 30-min intervals; it has been shown that 3 hr of continuous equilibration gave the same result. Variations in concentration between duplicate suspension samples were less than 5%;each experiment was repeated three times.The quantities of fungicide and clay used in these experiments were as follows: 4500 µg of benzimidazole and 1.5 g of Ca-bentonite.To the clear supernatant (20 ml), 10 ml of 3NNaOH was added. (If a 10-ml sample was taken, 10 ml of water was added.) The basic aqueous solution was extracted three times with 30 ml of ethyl acetate.

Since benzimidazole is much more soluble in water than TBZ or MBC, it was measured directly in the water by spectrophotometry, at 277 nm for the nonprotonated molecule or at 273 nm for the charged species, at the lower pH.Benzimidazole was almost not adsorbed on bentonite when the pH of the suspension was 7.

 

And supporting study from authoritative database (HSDB by US EPA) indicate the Koc of benzimidazole is estimated as 110, using a log Kow of 1.32 and a regression derived equation. This estimated Koc value suggests that 1H-benzimidazole (benzimidazole) is expected to have high mobility in neutral and basic soils.

 

Also predicted model support to all experimental results i.e the Soil Adsorption Coefficient i.e Koc value of 1H-benzimidazole was estimated using EPI suite KOCWIN Program (v2.00) program as Koc 214.6 L/kg (log Koc=2.33) by means of MCI method at 25 deg.C. This Koc value indicates that the substance 1H-benzimidazole has a Low sorption to soil and sediment and therefore have rapid to moderate migration potential to groundwater.

 

Thus above all available studies conclude the test chemical 1H-benzimidazole or benzimidazole (CAs no. 51-17-2) is not likely to adsorb on soil and thus it can be considered to be highly mobile in soil.

[LogKoc: 1.6871]