Reaction mass of tetrasodium 5-{[4-chloro-6-(4-{[2-(sulfonatooxy)ethyl]sulfonyl}anilino)-1,3,5-triazin-2-yl]amino}-4-hydroxy-3-[(4-{[2-(sulfonatooxy)ethyl]sulfonyl}phenyl) diazenyl]naphthalene-2,7-disulfonate and trisodium 5-({4-chloro-6-[4-(vinylsulfonyl) anilino]-1,3,5-triazin-2-yl}amino)-4-hydroxy-3-[(4-{[2-(sulfonatooxy)ethyl]sulfonyl}phenyl)diazenyl]naphthalene-2,7-disulfonate

Dissociation constant

Link to relevant study record(s)

Reference

Endpoint:

dissociation constant

Type of information:

experimental study

Adequacy of study:

key study

Study period:

03 May 2000 to 05 May 2000

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 112 (Dissociation Constants in Water)

Deviations:

no

GLP compliance:

no

Dissociating properties:

yes

No.:

#1

pKa:

>= 1.9 - <= 2.89

Temp.:

22 °C

Remarks on result:

other: for the acid range

No.:

#2

pKa:

>= 8.93 - <= 10.16

Temp.:

22 °C

Remarks on result:

other: alkaline range

The wavelengths 294 nm and 531 nm were chosen for the acid as well as for the alkaline range quantification. During pH measurement the temperature was determined as follows: Exp. 1: 21.5 to 22.2°C; Exp. 2: 22.3 to 22.8°C; Exp. 3: 22.3 to 23.4°C. The pH data were not corrected with acidity functions.

 

Tables 3 to 5 show the results of the determination of the dissociation constant in the acid range

 

Table 3:Results of experiments 1 and calculation of pK_a(SD = standard deviation)

Exp.	pH	Absorbance 294 nm	pKa294 nm	Absorbance 531 nm	pKa531 nm
1-7	6.82	0.8273	dm	0.4948	dm
1-6	5.37	0.8256	3.94	0.4905	4.51
1-5	4.68	0.8261	3.10	0.4901	3.86
1-4	3.40	0.8239	2.29	0.4881	2.76
1-3	2.29	0.8201	1.55	0.486	1.80
1-2	1.55	0.8066	1.44	0.4771	1.54
1-1	0.96	0.7801	di	0.4591	di
1		Mean (SD):	2.46 (±1.06)	Mean (SD):	2.89 (±1.28)

 

Table 4:Results of experiments 2 and calculation of pK_a(SD = standard deviation)

Exp.	pH	Absorbance 294 nm	pKa294 nm	Absorbance 531 nm	pKa531 nm
2-7	6.27	0.842	dm	0.4982	dm
2-6	5.44	0.8440	-^a)	0.4992	-^a)
2-5	4.75	0.8433	-^a)	0.4980	2.58
2-4	3.87	0.8407	2.55	0.4970	2.49
2-3	2.19	0.8330	1.60	0.4935	1.46
2-2	1.66	0.8221	1.54	0.4862	1.49
2-1	1.10	0.7946	di	0.4685	di
2		Mean (SD):	1.90 (± 0.57)	Mean (SD):	2.01 (± 0.61)

^a)The absorbance values do not allow the calculation of the pK_avalue

 

Table 5:Results of experiments 3 and calculation of pK_a(SD = standard deviation)

Exp.	pH	Absorbance 294 nm	pKa294 nm	Absorbance 531 nm	pKa531 nm
3-7	6.72	0.7866	dm	0.4705	dm
3-6	5.77	0.7880	-^a)	0.4698	4.08
3-5	4.31	0.7823	3.33	0.4652	3.56
3-4	3.24	0.7851	1.77	0.4675	2.21
3-3	2.62	0.7809	1.78	0.4631	2.05
3-2	1.54	0.7659	1.47	0.4532	1.53
3-1	0.78	0.7413	di	0.4355	di
3		Mean (SD):	2.09 (± 0.84)	Mean (SD):	2.69 (± 1.08)

^a)The absorbance value does not allow the calculation of the pK_avalue

 

Tables 6 to 8 show the results of the determination of the dissociation constant in the alkaline range

 

Table 6:Results of experiments 1 and calculation of pK_a(SD = standard deviation)

Exp.	pH	Absorbance 294 nm	pKa294 nm	Absorbance 531 nm	pKa531 nm
1-7	6.82	0.8273	dm	0.4948	dm
1-8	7.07	0.8280	-^a)	0.4950	-^a)
1-9	9.75	0.8273	-^a)	0.4835	8.58
1-10	10.20	0.8224	8.96	0.4698	9.41
1-11	10.63	0.8109	9.97	0.4334	10.35
1-12	11.32	0.7876	11.21	0.3585	11.83
1-13	12.38	0.7363	di	0.3168	di
1		Mean (SD):	10.05 (± 1.13)	Mean (SD):	10.04 (±1.39)

^a)The absorbance values do not allow the calculation of the pK_avalue

 

Table 7:Results of experiments 2 and calculation of pK_a(SD = standard deviation)

Exp.	pH	Absorbance 294 nm	pKa294 nm	Absorbance 531 nm	pKa531 nm
2-7	6.27	0.8429	dm	0.4982	dm
2-8	6.55	0.8441	-^a)	0.4978	3.90
2-9	9.57	0.8440	-^a)	0.4871	8.39
2-10	10.36	0.8377	9.05	0.4615	9.77
2-11	10.63	0.8200	10.04	0.4350	10.36
2-12	11.47	0.7921	11.39	0.3448	12.23
2-13	12.47	0.7306	di	0.3180	di
2		Mean (SD):	10.16 (± 1.17)	Mean (SD):	8.93 (± 3.13)

^a)The absorbance values do not allow the calculation of pK_avalue

 

Table 8:Results of experiments 3 and calculation of pK_a(SD = standard deviation)

Exp.	pH	Absorbance 294 nm	pKa294 nm	Absorbance 531 nm	pKa531 nm
3-7	6.72	0.7866	dm	0.4705	dm
3-8	6.91	0.7839	5.33	0.4680	5.08
3-9	8.62	0.7874	-^a)	0.4661	7.05
3-10	9.69	0.7876	-^a)	0.4588	8.56
3-11	11.01	0.7594	10.55	0.3721	11.15
3-12	12.02	0.7177	12.29	0.3037	13.78
3-13	12.54	0.6806	di	0.3008	di
3		Mean (SD):	9.39 (± 3.62)	Mean (SD):	9.12 (± 3.42)

^a)The absorbance values do not allow the calculation of the pK_avalue

Conclusions:

The dissociation constant of the test substance at room temperature (circa 22°C) was determined within this study as pKa between 1.90 and 2.89 for the acid range, using the five mean values of three experiments.

The pKa value for the alkaline range was determined within this study as pKa between 8.93 and 10.16 based on five mean values obtained from of three experiments.

Executive summary:

The determination of the pK_ain the acid and alkaline range was carried out according to the OECD guideline no. 112.

 

The dissociation constant of the test substance at room temperature (circa 22°C) was determined within this study as pK_abetween 1.90 and 2.89 for the acid range, using the five mean values of three experiments.

 

The pK_avalue for the alkaline range was determined within this study aspK_abetween 8.93 and 10.16 based on five mean values obtained from of three experiments.

 

The quoted guideline demands pure or commercial grade substances for carrying out the described test methods. The test substance has a purity of about 71 %. Possible effects of impurity on the results has therefore not been assessed.

Description of key information

The dissociation constant of the test substance at room temperature (circa 22°C) was determined within this study as pKa between 1.90 and 2.89 for the acid range, using the five mean values of three experiments.

Additional information

The determination of the pK_ain the acid and alkaline range was carried out according to the OECD guideline no. 112.

 The dissociation constant of the test substance at room temperature (circa 22°C) was determined within this study as pK_abetween 1.90 and 2.89 for the acid range, using the five mean values of three experiments.

 

The pK_avalue for the alkaline range was determined within this study aspK_abetween 8.93 and 10.16 based on five mean values obtained from of three experiments.

 

The quoted guideline demands pure or commercial grade substances for carrying out the described test methods. The test substance has a purity of about 71 %. Possible effects of impurity on the results has therefore not been assessed.