Benzoyl chloride, 3-methoxy-2-methyl-

Adsorption / desorption

Administrative data

Endpoint:

adsorption / desorption, other

Type of information:

experimental study

Adequacy of study:

key study

Study period:

24 October 1996 - 29 January 1997

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study conducted to GLP 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.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1997

Report date:

1997

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

other: The estimation of the soil adsorption coefficient (Koc) by high performance liquid chromatography (HPLC) method as described in OECD draft document TGP/94.75 (April 1994).

Deviations:

no

Principles of method if other than guideline:

The test substance hydrolyses almost immediately in contact with water. Therefore the soil adsorption coefficient has been determined on the hydrolysis product MMBA (3-methoxy-2-methylbenzoic acid).

GLP compliance:

yes

Type of method:

HPLC estimation method

Media:

soil

Test material

Test material information

Constituent 1

Reference substance name:

3-methoxy-2-methyl benzoic acid

IUPAC Name:

3-methoxy-2-methyl benzoic acid

Test material form:

solid: particulate/powder

Remarks:

migrated information: powder

Details on test material:

MMBA
Appearance: white powder
Storage conditions: room temperature

Radiolabelling:

no

Study design

HPLC method

Details on study design: HPLC method:

INSTRUMENTATION AND APPARATUS
HPLC system
Autosampler: Model 712 WISP, Waters Associates.
Pump: Model 510, Waters Associates.
Detector: Model 484, Waters Associates.
Data handling system: Model 1020, PE Nelson.
Plotter: Model Diconix 180si, Kodak.

Analytical balance: Model AT261, Mettler-Toledo.
Autopipette: Model EPD 10 mL, Anachem.
Ultrasonic bath: Model FS 300b. Decon Laboratories.
Water: Double glass-distilled.


MEASUREMENT OF THE DEAD TIME
The dead time (the average time a solvent molecule needs to pass through the column) was taken as 3.362 minutes, the time of the earliest consistently appearing peak (mean of 3.360 and 3.363) Thiourea, a recommended organic compound for the measurement of the dead time, was used.

PREPARATION OF REFERENCE MIXTURE
The reference compounds used were Monolinuron, Linuron, Pyrazophos, Trifluralin, Sulprofos and Isofenphos. Stock solutions were prepared as follows: Monolinuron and Trifluralin ca 0.05 g into 50 mL, Sulprofos ca 0.1 g into 50 mL, Isofenphos and Linuron ca 0.1 g into 100 mL and Pyrazophos ca 0.2 g into 100 mL. All stock solutions were diluted to volume with methanol. Differing volumes of each reference stock were pipetted into a volumetric flask and diluted to 100 mL with methanol so that the chromatogram of the reference mixture would contain peaks of approximately the same height.

PREPARATION OF TEST SOLUTIONS
Test substance 0.01934 g (test A) and 0.01901 g (test B) was weighed into a volumetric flask and diluted to 20 mL with methanol.
An aliquot (3.5 mL) of each solution was diluted to 100 mL with methanol.
The quantity of test substance introduced onto the HPLC column in a 20 µL injection was 676.90 ng for test A and 665.36 ng for test B.

PREPARATION OF THIOUREA SOLUTION
A stock solution of concentration of 1026.0 µg/mL was prepared by weighing 0.05130 g into a 50 mL volumetric flask and dissolving in and diluting to volume with methanol. This solution was diluted 3 mL to 100 mL with methanol in the reference mixture, to produce a concentration of 30.780 µg/mL.

HPLC CONDITIONS
Column: Apex Cyano, 25 x 4.6 mm id. 5 µ particle size.
Mobile phase: Water/methanol, 50:50, v/v.
Flow rate: 1.0 mL/min.
Pressure: 2500 psi.
Analytical wavelength: 220 nm.
Injection volume: 20 µL.
Range: -5 to 275 mV.

CALCULATION
The retention time (tR) of each reference compound was measured, and the capacity factor (k) calculated as follows:

k = (tR - tO) / (tO)

where tO = dead time
tR = retention time of reference compound

A plot was made of log k versus log Koc for the reference compounds. A linear regression was also performed on the data, using the equation:

log k = I + S log Koc

where I and S are the intercept and slope respectively.


The retention time of the test substance was used to calculate a log k value from the equation:

log k = log [(tM - tO) / tO)

where tM = retention time of the test substance
tO = dead time
k = capacity factor for the test substance

This was then used to determine log Koc of the test substance as follows:

Log Koc = (log K - I) / S

where I = intercept described from linear regression of reference compound
S = slope derived from linear regression of reference compound

Results and discussion

Adsorption coefficient

Adsorption coefficient 1

Type:

Koc

Value:

< 60.3

Adsorption coefficient 2

Type:

log Koc

Value:

< 1.78

Results: HPLC method

Details on results (HPLC method):

Calibration data for the reference compounds are given in Table 1. The dead time (tO) was determined as 3.362 minutes (mean of 3.36 and 3.363 minutes) and the mean retention times of the reference compounds ranged from 5.939 to 30.459 minutes. This resulted in values of log k in the range - 0.11548 to 0.90632.

A linear regression analysis of the results provided a slope of 0.38284, an intercept of -0.80342 and a correlation coefficient of 0.98579.

Analytical data for the test substance are given in Table 2. A mean retention time of 2.200 minutes was obtained. The test substance was found to retain on the HPLC column for a shorter period of time than any of the reference compounds. Therefore the log Koc value will be quoted as less than 1.78 (the Koc value for the fastest eluting reference compound, Monolinuron) and thus Koc as less than 60.3.

No significant peaks were obtained in the chromatograms of the blank solutions.

Using the calculated regression equation and the experimentally determined log k values, the log Koc values of the individual reference compounds were calculated and found to be within ± 0.27 log units of their literature values. Therefore the result will be quoted to this accuracy.

Any other information on results incl. tables

Table 1 Calibration Data: Reference Compounds

Reference Compound	Literature Value Log Koc	Conc. Used in Stock Reference Solutions (µg/mL)	Quantity Introduced onto Column (ng)	Retention Time (minutes)			K	Log K
				1^stInjection	2^ndinjection	3^rdInjection
Monolinuron Linuron Isofenphos Pyrazophos Trifluralin SuIprofos	1.78 2.59 2.94 3.65 3.94 4.46	81.285 61.452 114.05 220.67 302.46 308.13	1625.7 1229.0 2281.0 4413.4 6049.2 6162.6	5.947 8.183 11.547 13.797 23.297 30.617	5.930 8.143 11.480 13.687 23.150 30.300	5.939 8.163 11.514 13.742 23.224 30.459	0.76651 1.4280 2.4247 3.0874 5,9078 8.0598	-0.11548 0.15473 0.38466 0.48959 0.77143 0.90632

 

Table 2 Test Substance Analytical Data

Retention Time (minutes)			Log Koc	Koc
Test A	Test B	Mean
2.193	2.207	2.200	<1.78	<60.3

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

The soil adsorption coefficient of the test substance was determined to be:
Koc = <60.3
Log Koc = <1.78
The result indicates that the test substance is likely to be highly mobile in soils.

Executive summary:

The adsorption coefficient of the test substance was determined using a High Performance Liquid Chromatography method. A HPLC system fitted with a cyanopropyl analytical column was used to measure the retention times of the test substance and the selected reference compounds. The cyanopropyl column had both polar and non-polar isolates and therefore allowed for the interaction of polar and non-polar groups of the molecules in a similar way to the organic matter in soil.

The dead time of the HPLC system was determined by the use of thiourea, a suitable inert substance that was not retained by the column. The capacity factors (k) for the test substance and reference substances were then calculated and the log k values were plotted against their adsorption coefficient values (log Koc) to construct a calibration curve. The calibration curve was used to estimate the adsorption coefficient of the test substance. The estimated log Koc for the test substance was < 1.78 (Koc = < 60.3). The potential mobility of the test substance is therefore likely to be high.