2,3,5,6-tetrachloropyridine

Hydrolysis

Administrative data

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

16 January 1991 to 19 February 1992

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP study conducted in compliance with agreed protocols, with only minor deviations from standard test guidelines.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1992

Report date:

1992

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Deviations:

yes

Remarks:

Details of buffer solutions not specified.

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

2,3,5,6-tetrachloropyridine

EC Number:

219-283-9

EC Name:

2,3,5,6-tetrachloropyridine

Cas Number:

2402-79-1

Molecular formula:

C5HCl4N

IUPAC Name:

2,3,5,6-tetrachloropyridine

Details on test material:

Lot number WP900914-748 of purity = 98.6%

Study design

Analytical monitoring:

yes

Details on sampling:

All hydrolysis reaction mixtures were prepared under aseptic conditions. Glassware, reaction vessels and septa were sterilised by autoclaving for 30 minutes at 121 deg C. All buffers were prepared at 0.1 M and fliter sterilised (0.2 µm). Duplicate vials were sacrificed at regular time intervals for extraction and analysis. Samples were extracted for 30 minutes with an equal volume of cyclohexane. Extraction efficiency was determined to be 100%. Samples were analysed as previously described.

Buffers:

Not specified.

Details on test conditions:

Preliminary experiments were conducted to examine the effect of pH on hydrolysis. Initial hydrolysis studies were performed for 5 days at 50.0 ± 0.1 °C using sterile, buffered aqueous solutions at a pH of 4, 7 and 9. All samples were incubated in the dark. Subsequent hydrolysis studies were run at 25.0 ± 0.1 °C and 40.0 ± 0.1 °C for 31 days over the same pH range from 4 to 9. Buffers were prepared following OECD guidelines using biphthalate, phosphate, and borate (5).

Hydrolysis mixtures for the long-term (31 days) studies were prepared in sealed reaction vessels. Reaction mixtures were constructed by filling 10 mL serum vials with 10 mL of an aqueous buffer solution. The test solutions were spiked with the test material at an initial concentration of 10 mg/L. The serum vials were sealed with Teflon®-coated, butyl rubber septa and aluminum crimp seals.

All hydrolysis reaction mixtures were prepared under aseptic conditions. Glassware, reaction. vessels and septa were sterilized by autoclaving for 30 min at 121 °C. All buffers were prepared at 0.1 M and filter sterilized (0.2 pm.). Duplicate vials were sacrificed at regular time intervals for extraction and analysis. Samples were extracted for 30 min with an equal volume of cyclohexane. Extraction efficiency was determined to be 100 %. Samples were analyzed as previously described.

Additional studies were conducted to identify the products of hydrolysis. To ensure the recovery of both parent and degradation products, all reactions were set in sealed glass ampules at an initial concentration of 10 mg/L. Parent and degradation products were determined by high pressure liquid chromatography (HPLC) using a YMC-Basic® column coupled to a UV detector. The mobile phase was 60:40 acetonitrile:water with 0.1 % phosphoric acid delivered at a flow rate of 1.0 mL/min.

Duration of test

Duration of test 1

Duration:

5 d

Duration of test 2

Duration:

31 d

Duration of test 3

Duration:

10 d

pH:

9

Results and discussion

Transformation products:

not measured

Details on hydrolysis and appearance of transformation product(s):

The hydrolysis of Sym-Tet, as determined according to OECD method 111, was negligible after 5 days at 50 °C at a pH of either 4 or 7. Hydrolysis was only noted at pH 9 where a loss of 18 % of the parent compound was observed (data not shown). However, this loss may not have been due to hydrolysis, since the predicted hydrolysis product, trichloropyridinol, was not detected. Additional hydrolysis reactions were set in sealed glass ampules to facilitate mass balance recovery. All reactions were prepared at a pH of 9 and incubated for 10 days at 70°C. Prior to sample analysis, the test vessels were rinsed twice with an equal volume of acetonitrile to eliminate the possibility of test material losses due to adsorption. Acetonitrile washes were combined with the aqueous samples for HPLC analysis. After 10 days, Syrn-Tet recovery was > 98 %, and no trichloropyridinol was detected. The results from these studies demonstrated that 'Sym-Tet was hydrolytically stable at all three pHs up to 70 °C.

Details on results:

The results of the hydrolysis experiments demonstrated that Sym-Tet was hydrolytically stable over a pH ranging from 4 to 9 and at elevated temperatures (> 50°C). In general, halogenated, aromatic hydrocarbons belong to a class of organic functional groups that have been reported to be resistant to hydrolysis. Mechanistically, the chlorine substituents of Sym-Tet are not easily displaced due to electron resonance stabilization by the aromatic pyridine ring. Based on the results of this study, Sym-Tet would be hydrolytically stable under environmental conditions.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

The results of the hydrolysis experiments demonstrated that Sym-Tet was hydrolytically stable over a pH ranging from 4 to 9 and at elevated temperatures (> 50°C). Based on the results of this study, Sym-Tet would be hydrolytically stable under environmental conditions.

Executive summary:

The hydrolysis of Sym-Tet, as determined according to OECD method 111, was negligible after 5 days at 50 °C at a pH of either 4 or 7. Hydrolysis was only noted atpH 9 where a loss of 18 % of the parent compound was observed (data not shown).However, this loss may not have been due to hydrolysis, since the predicted hydrolysis product, trichloropyridinol, was not detected. Additional hydrolysis reactions were set in sealed glass ampules to facilitate mass balance recovery. All reactions were prepared at a pH of 9 and incubated for 10 days at 70°C. Prior to sample analysis, the test vessels were rinsed twice with an equal volume of acetonitrile to eliminate the possibility of test material losses due to adsorption. Acetonitrile washes were combined with the aqueous samples for HPLC analysis. After 10 days, Sym-Tet recovery was > 98 %, and no trichloropyridinol was detected. The results from these studies demonstrated that Sym-Tet was hydrolytically stable at all three pHs up to 70 °C.