Pyridine-2,6-dicarboxylic acid

Water solubility

Administrative data

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2018

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Deviations:

not specified

GLP compliance:

no

Type of method:

flask method

Test material

Test material information

Constituent 1

Reference substance name:

Pyridine-2,6-dicarboxylic acid

EC Number:

207-894-3

EC Name:

Pyridine-2,6-dicarboxylic acid

Cas Number:

499-83-2

Molecular formula:

C7H5NO4

IUPAC Name:

pyridine-2,6-dicarboxylic acid

Test material form:

solid: crystalline

Results and discussion

Water solubility

Key result

Water solubility:

>= 4.29 - <= 4.39 mg/L

Conc. based on:

test mat.

Loading of aqueous phase:

20 g/L

Incubation duration:

ca. 3 d

Temp.:

20.5 °C

pH:

ca. 2.06

Any other information on results incl. tables

1.1         

The data which was acquired during equilibration time (flask 1A-C, days 1 – 3) is presented in the following table:

Table6.1‑a          Equilibration phase

Time [d] (flask)	Temperature [°C]	pH*	Dilution factor	Peak area [mAU*min]	Measured values [g/L]	QC recovery [%]	Difference to previous sample [%]
1 (1A)	20.0	2	50	52.7790	4.20	103.5	-
				55.4003
2 (1B)	20.2	2	50	55.8347	4.35		+3.5
				56.0249
3 (1C)	20.1	2	50	52.9536	4.18		-3.9
				54.6433

* pH during equilibration phase was tested using pH paper.

1.2         

Table6.2‑a          Measurements at the plateau

Flask	Temperature [°C]	pH*	Dilution factor	Peak area [mAU*min]	Measured values [g/L]	QC recovery [%]
Blank	20.3	7	-	-	< LOQ	103.5
				-
2	20.5	2.08	50	55.0015	4.29
				55.3979
3	20.5	2.08	50	55.6454	4.34
				55.9294
4	20.5	2.06	50	55.1212	4.30
				55.5387
5	20.5	2.06	50	55.8959	4.36
				56.2620
6	20.5	2.05	50	55.6743	4.39
				57.2188

* pH at the plateau was tested using a calibrated pH meter. Blank was tested using pH paper.

The measurements of flasks 2-6 were used for the calculation of the mean.

Table6.3‑a          Measurements used for Calculation of Solubility

Flask	Concentration [g/L]	Total Mean [g/L]	Total Standard Deviation [g/L] (Relative standard deviation [%])
2	4.29	4.34	0.08 (1.8)
3	4.34
4	4.30
5	4.36
6	4.39

 

Mean at the plateau is 4.34±0.08 g/L.

Applicant's summary and conclusion

Conclusions:

The solubility of Dipicolinic acid (DPA) in water was determined from the measured test item concentrations in the filtrated test solutions.
Equilibration time can be considered as approximately 1 day, as the measured values after 1 and 3 d did not give significantly different values and did not show upward tendency.
Because of a difference of less than 15 % in the concentrations on days 2 and 3 and no upward tendency, the test was finished on day 3.
All replicates showed good correspondence. Standard deviation of the five flasks which were used for the calculation of water solubility at the plateau was 0.08 g/L, corresponding to a relative standard deviation of 1.8 %.
The pH value was 2.05 – 2.08 in all five flasks, the test temperature was in the acceptable range with 20.0 – 20.5 °C over the test duration (measured in the liquid at sampling time points).
No observations arousing doubts concerning the accuracy of the results and the validity of the study were made.

Executive summary:

The solubility of the test itemDipicolinic acid (DPA) in water was determined by measurement of the test item concentration in the filtrated test solutions using HPLC.

In the pre-test, a test item-water mixture with nominal concentration 1 g/L appeared after 10 min. shaking turbid, but was after 18 h shaking clear. Additionally test item-water mixtures with nominal concentrations 10 g/L resp. 50 g/L were shaken for 21 h, and 3.44 resp. 3.77 g/L test item were measured after sample preparation in the filtrates. Thus solubility was estimated to be approx. 4 g/L in the pre-test.

Therefore the flask method was used according to the guideline.

In the main test,the loading rate 20 g/L, corresponding to 5 fold excess, was chosen for all flasks. Three flasks 1A - C with the same loading rate were used during equilibration. Seven vessels (flasks blank, 1C (for the sampling point 1 d) and 2 – 6) were set onto the shaking apparatus immediately. After 1 d, flask 1B (for the sampling point 2 d) and after 2 d, flask 1A (for the sampling point 1 d) were set on the shaker and all flasks were shaken for further 24 hours at room temperature (20.0 ± 0.5 °C). Then, flasks 1A - 1C were taken from the shaker, samples were taken, membrane filtered and analysed. 

Because of a difference of less than 15 % in the concentrations on days 2 and 3 and no upward tendency, the test was finished on day 3.

The final measurement was performed as determination from flasks 2 – 6 after 3 d shaking. All filtrated test solutions showed no Tyndall effect (i.e. a laser beam was not scattered when transmitted through the liquid).

At the plateau, the concentration of Dipicolinic acid (DPA) in water had reached.

 4.34 ± 0.08 g/L at 20.5 °C

= 4.34 ± 0.08 kg/m³(SI units) (mean value ± standard deviation of five individual vessels