2-(N-methyl-p-toluidino)ethanol

Partition coefficient

Administrative data

Endpoint:

partition coefficient

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2019

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 117 (Partition Coefficient (n-octanol / water), HPLC Method)

Version / remarks:

The following deviation from the study plan was documented:
• In the preliminary test, a diluted test item solution with a concentration of 100 mg/L was measured instead of the stock solution with a concentration of 1 g/L. This is considered uncritical since the test item peaks were sufficiently strong.
The deviation was signed and assessed by the study director on 12. Apr. 2019.

Deviations:

yes

Remarks:

The following deviation from the study plan was documented: see remarks

GLP compliance:

yes (incl. QA statement)

Type of method:

HPLC method

Partition coefficient type:

octanol-water

Test material

Test material information

Constituent 1

Reference substance name:

2-(N-methyl-p-toluidino)ethanol

EC Number:

220-638-5

EC Name:

2-(N-methyl-p-toluidino)ethanol

Cas Number:

2842-44-6

Molecular formula:

C10H15NO

IUPAC Name:

2-[methyl(4-methylphenyl)amino]ethan-1-ol

Test material form:

liquid: viscous

Study design

Analytical method:

high-performance liquid chromatography

Results and discussion

Partition coefficient

Key result

Type:

log Pow

Partition coefficient:

ca. 2.2

Temp.:

25 °C

pH:

ca. 6

Any other information on results incl. tables

1      Findings and Results

1.1     Reference Items

1.1.1   Measurement Data

The retention times which were recorded for the reference items are presented in the following table.

Table9.1‑a    Retention Times (RT) Reference Items and Dead Time Marker

Compound	RT 1	RT 2	RT 3	RT 4	RT 5	RT 6
	min.	min.	min.	min.	min.	min.
Thiourea	1.410	1.413	1.413	1.410	1.410	1.410
2-Butanone	1.877	1.877	1.877	1.873	1.877	1.873
Benzyl alcohol	2.223	2.227	2.223	2.223	2.223	2.223
Acetophenone	2.760	2.760	2.760	2.760	2.760	2.760
Nitrobenzene	3.260	3.260	3.260	3.257	3.257	3.257
Benzene	4.570	4.570	4.570	4.570	4.570	4.567
Toluene	7.187	7.190	7.190	7.187	7.187	7.187
Naphthalene	10.067	10.070	10.070	10.063	10.063	10.060

 

1.1.2   Calculated Values

For each reference item, the calculated capacity factors are presented in the following table.

Table9.1‑b    Capacity Factors Reference Items and Dead Time Marker

Compound	Retention Time Mean	Retention Time Standard  Deviation	Retention Time Relative Standard Deviation	k
	min.	min.	%
Thiourea	1.411	0.002	0.122	0.0000
2-Butanone	1.876	0.002	0.092	0.3291
Benzyl alcohol	2.224	0.001	0.061	0.5760
Acetophenone	2.760	0.000	0.000	0.9559
Nitrobenzene	3.258	0.002	0.056	1.3091
Benzene	4.569	0.001	0.030	2.2382
Toluene	7.188	0.002	0.024	4.0937
Naphthalene	10.066	0.004	0.040	6.1331

 

1.1.3   log P_OW/ log k

The values for log k and log P_OWof the reference items are presented in the following table:

Table9.1‑c    log k and log P_OWof Reference Items

Compound	log k	log POW
2-Butanone	-0.4826	0.3
Benzyl alcohol	-0.2396	1.1
Acetophenone	-0.0196	1.7
Nitrobenzene	0.1170	1.9
Benzene	0.3499	2.1
Toluene	0.6121	2.7
Naphthalene	0.7877	3.6

 

Figure9.1‑a   Graphical Representation of the Correlation of log k and log P_OW

 

1.1.4   Correlation Results

Dead time is 1.411 ± 0.002 minutes, with RSD (relative standard deviation) 0.122 %.

 

The RSD of the retention times of the reference items lay all below 0.10 %.

 

Equation of the regression:

log k = 0.4187 * log P_OW– 0.6407
with a coefficient of determination r²= 0.9615

 

 

1.2     Test ItemN-(2-Hydroxyethyl)-N-Methyl-p-Toluidine (MHPT)

1.2.1   Measurement Data

The retention times of the test item are presented in the following table:

Table9.2‑a      Retention Times (RT) Test Item

Measurement	RT 1	RT 2
	min.	min.
Measurement 1	2.710	4.223
Measurement 2	2.710	4.220
Measurement 3	2.707	4.220
Mean	2.709	4.221
Standard Deviation	0.002	0.002

 

Table9.2‑b    Peak Areas Test Item

Measurement	Area Peak 1	Relative Area Peak 1	Area Peak 2	Relative Area Peak 2
	mAU*min	%	mAU*min	%
Measurement 1	4.3866	3.92	107.4607	96.08
Measurement 2	4.4003	3.95	107.0349	96.05
Measurement 3	4.3727	3.95	106.3806	96.05
Mean	4.3865	3.94^1	106.9587	96.06
Relative Standard Deviation	-	0.39	-	0.02

¹As the peak area of peak 1 was < 5 %, this peak was considered a minor peak.

1.2.2   Calculated Values

The calculated values are presented in the following table:

Table9.2‑c    Capacity Factor, log Capacity Factor, log P_OWTest Item Peaks

Peak	Measurement No.	k	log k	log POW
1	1	0.9205	-0.0360	1.4
	2	0.9205	-0.0360	1.4
	3	0.9181	-0.0371	1.4
	Mean	-	-	1.4
	Standard Deviation	-	-	0.0
2	1	1.9929	0.2995	2.2
	2	1.9906	0.2990	2.2
	3	1.9906	0.2990	2.2
	Mean	-	-	2.2
	Standard Deviation	-	-	0.0

 

The log P_OWwas calculated from the capacity factors as follows:

 

log P_OW= (log k + 0.6407) / 0.4187

 

1.3     Result and Validity

1.3.1   Result

As peak 1 showed a relative area < 5 %, it was considered a minor peak.

Although area is not necessarily correlated to absolute concentration if a UV detector is used, it is assumed that the test item consists mainly of peak 2. Using the correlation log k / log P_OW, the log P_OWof the major component of the test itemN-(2-Hydroxyethyl)-N-Methyl-p-Toluidine (MHPT)was calculated as 2.2 ± 0.0 (mean ± standard deviation).

1.3.2   Validity

The validity criteria and results are presented in the following table:

Table9.3‑a      Validity Criteria and Results

Peak	Parameter	Criterion	Found	Assessment
1	Range (Max – Min. log POW)	< 0.1	0.003	valid
	Value within Range of Ref. Items	0.30 - 3.60	1.444	valid
2	Range (Max – Min. log POW)	< 0.1	0.001	valid
	Value withinofItems	0.30 - 3.60	2.245	valid

 

Applicant's summary and conclusion

Conclusions:

Variations in the retention times of reference items and test item were very small, demonstrating a stable configuration of the HPLC-column. The correlation log k / log POW is good: the coefficient of determination r2 was calculated with 0.9615. This value was considered as sufficiently high to use the calibration function for the determination of the log POW of the test item N-(2-Hydroxyethyl)-N-Methyl-p-Toluidine (MHPT). As peak 1 showed a relative area < 5 %, it was considered a minor peak. Although area is not necessarily correlated to absolute concentration if UV detection is used, it is assumed that the test item N-(2-Hydroxyethyl)-N-Methyl-p-Toluidine (MHPT) consists mainly of peak 2, indicating that the log POW should be stated as 2.2 ± 0.0 (mean ± standard deviation) at a temperature of 25 ± 0.5 °C. No observations were made which might cause doubts concerning the validity of the study outcome.

Executive summary:

The study was performed using a HPLC with a C18 column. Seven reference items with different retention times and thiourea for the determination of the dead time were used to produce a calibration curve, since retention time on hydrophobic columns and P_OWare correlated. The reference items were chosen based on the results of the pre-test.

One vial was filled with the reference item mix and one vial with the test item solution. The vials were analysed using the HPLC with the program described below. First one injection from the solvent blank methanol/water 65/35 (v/v) was made. Then three injections were measured from the reference item mix, three injections from the test item and again three injections from the reference item mix.

For each reference item, the capacity factor k was calculated from the retention time of thiourea and the retention time of the respective reference item.

A calibration function (log k versus log P_OW, linear fit) was determined using the literature values for the log P_OWof the reference items and the retention times in the six determinations.

The chromatogram of the test item gave one major and one minor peak. With the calibration function log k versus log P_OW, the corresponding log P_OWvalues of the two peaks were determined with:

 

Peak	Mean Retention Time [min]	Mean Area [mAU*min][1]	Relative Area [%]	log POW ±Standard Deviation
1	2.709	4.3865	3.94^2	1.4 ± 0.0
2	4.221	106.9587	96.06	2.2 ± 0.0

²As the peak area of peak 1 was < 5 %, this peak was considered a minor peak.

 

These values are the means ± standard deviations of three independent determinations

As peak 1 showed a relative area < 5 %, it was considered a minor peak and is not taken into account in the determination of log P_OWof the test item.

Although area is not necessarily correlated to the absolute concentration, if a UV detector is used, it is assumed that the test item consists mainly of peak 1. Thus, the log P_OWof the test item N-(2-Hydroxyethyl)-N-Methyl-p-Toluidine (MHPT) is stated as 2.2 ± 0.0 at a temperature of 25 ± 0.5 °C.