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Description of key information

Adsorption / desorption:

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.

Additional information

Adsorption / desorption:

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 dimensionless, 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 concluded 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.