polymeric zinc propylenebis(dithiocarbamate);propineb (ISO)

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: EC Commission Directives 94/37/EC

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: 95/36/EC amending EC-Council Directive 91/414/EC

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 835.2120 (Hydrolysis of Parent and Degradates as a Function of pH at 25°C)

Qualifier:

according to guideline

Guideline:

EPA OPPTS 835.2130 (Hydrolysis as a Function of pH and Temperature)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Radiolabelling:

yes

Remarks:

[Propane-1-14C]

Analytical monitoring:

yes

Details on sampling:

Sampling intervals for Test 1 (pre-test, 50 °C) were 0, 0.25, 1, 1.25, 2 and 5 days (pH 4), 0, 0.25, 1, 1.25, 2 and 5 days (pH 7) and 0, 0.25, 1, 1.25, 2, 4 and 7 days (pH 9). In Test 2 (main test, 25 °C) samples were taken after 0, 0.25, 1, 2, 5, 9 and 27 days (pH 4); 0, 0.25, 1, 2, 5, 9 and 27 days (pH 7) and 0, 0.25, 1, 2, 6 and 10 days (pH 9). Sampling intervals for Test 3 (optional test, 20 °C) were 0, 0.25, 1, 2, 5, 9, 16 and 34 days (pH 4); 0, 0.25, 1, 2, 4, 8, 18 and 35 days (pH 7) and 0, 0.25, 1, 3, 7, 17 and 34 days (pH 9). At each sampling interval, the radioactivity in duplicate samples was determined by LSC. The transformation products were determined by reversed-phase HPLC/radiodetection. Identification of transformation products was performed by HPLCMS(/MS) as well as by HPLC co-chromatography or profile comparison.

Buffers:

The hydrolysis of radiolabeled [Propane-1-14C]Propineb was studied in the dark at 50 °C, 25 °C and 20 °C in sterile aqueous buffer solutions at pH 4 (0.01 M acetate buffer), pH 7 (0.01 M TRIS buffer), and pH 9 (0.01 M borate buffer) for a maximum of 35 days. The buffer solutions were prepared using highly purified and sterilized water and were bubbled with nitrogen to reduce influence of oxygen.

Details on test conditions:

The 10-mL glass crimp-top vials were closed with Teflon-faced septa and placed in a temperature-controlled water bath. During the entire test period the incubation temperature was recorded at least once at each working day. The recorded temperatures were confirmed by means of a calibrated thermometer for representative sampling intervals. The experiments were performed under dark conditions. At every sampling interval the samples were subjected to a pH check. At all test intervals samples were subjected to a sterility check.

An aliquot (100 µL) of the samples was applied to a mixed culture medium and incubated at ambient conditions in the dark for at least 43 days. The preparation of the culture medium and details of the microbiological test for the sterility of the solutions.

Number of replicates:

2

Positive controls:

no

Negative controls:

no

Statistical methods:

Arithmetic means were used in case of all LS measurements.
No rejection criteria were used.

Test performance:

Propineb is not stable in aqueous solutions. Therefore, it was directly applied as solid to
the test buffer solutions. Due to the insolubility and fast degradation of the test item, the
test item was not detectable with chromatographic methods.

Transformation products:

yes

No.:

#2

No.:

#1

% Recovery:

>= 94.6

Temp.:

50 °C

Remarks on result:

other: value was identical for all pH's (4,7,9)

Key result

pH:

4

Temp.:

20 °C

DT50:

0.5 h

Remarks on result:

other: Value was the same for all temperatures (50°C, 25°C, 20°C)

Key result

pH:

7

Temp.:

20 °C

DT50:

0.5 h

Remarks on result:

other: Value was the same for all temperatures (50°C, 25°C, 20°C)

Key result

pH:

9

Temp.:

20 °C

DT50:

0.5 h

Remarks on result:

other: Value was the same for all temperatures (50°C, 25°C, 20°C)

Other kinetic parameters:

Propineb is an oligomer and regarded as practically insoluble in water. After application,
the suspension was homogenized and immediately injected on a HPLC system. For
practical reasons, the time between application and injection was about 0.5 hours. The
results of the HPLC analysis indicate that Propineb was completely decomposed after
30 minutes exposed to room temperature at pH 4, pH 7 and pH 9. Therefore, the DT50
and the DT90 values were estimated to be less than 30 minutes at pH 4, pH 7 and pH 9.
Due to the fast degradation it is not possible to evaluate the degradation kinetics
according to FOCUS

The quotient of peaks areas formed by degradation products [counts] divided by applied
RA was constant from the first sampling over the entire sampling time for pH 7 and pH 9
samples while the dissolution was somewhat slower for pH 4 samples.

Test No/ Temperature	pH	Single First Order Kinetics [days]
		DT50	DT90
Test 1 / 50°C	4	<< 0.5 hours	<<0.5 hours
Test 1 / 50°C	7
Test 1 / 50°C	9
Test 2 / 25°C	4
Test 2 / 25°C	7
Test 2 / 25°C	9
Test 3 / 20°C	4
Test 3 / 20°C	7
Test 3 / 20°C	9

 

Validity criteria fulfilled:

yes

Conclusions:

Propineb is not stable in aqueous solution and shows a spontaneous reaction.

The main product of hydrolysis was PTU amounts as well as the amounts of PTU remained on a similar level from DAT-1 or DAT-2 onwards.

It was not possible to calculate hydrolysis half-lives DT50 of Propineb under the test conditions as Propineb does not dissolve in water.

Since the total amount of radioactivity represented transformation products already for the first sampling interval (about 0.5 hours after application), it might be concluded that the DT50 is less than 0.5 hours at pH 4, pH 7 and pH 9 for all temperatures.

Executive summary:

The hydrolysis of radiolabeled [propane-1-¹⁴C]Propineb was studied in the dark at 50, 25 and 20 °C in sterile aqueous buffer solutions at pH 4 (0.01 M acetate buffer), pH 7 (0.01 M TRIS buffer), and pH 9 (0.01 M borate buffer) for a maximum of 35 days. The buffer solutions were prepared using highly purified and sterilized water and were bubbled with nitrogen to reduce influence of oxygen before application. The nominal concentration of the test item was 1 mg/L.

 

Due to this insolubility, 0.1 mg [propane-1-¹⁴C]propineb was directly applied in solid state to each test system consisting of 100 mL buffer solution. All mixtures were sonicated for 5 minutes and analysed by HPLC/radiodetection within about 0.5 hours (first sampling interval, DAT-0). LSC measurements performed after about 24 hours of incubation demonstrated that about the entire amount of the applied radioactivity (100% of AR) had been dissolved within that time.

 

Sampling intervals for Test 1 for pH4 and pH7 (pre-test, 50 °C) were 0, 0.25, 1, 1.25, 2 and 5 days and 0, 0.25, 1, 1.25, 2, 4 and 7 days (pH 9). In Test 2 (main test, 25 °C) for pH4 and pH 7 samples were taken after 0, 0.25, 1, 2, 5, 9 and 27 days and 0, 0.25, 1, 2, 6 and 10 days (pH 9). Sampling intervals for Test 3 (20 °C) were 0, 0.25, 1, 2, 5, 9, 16 and 34 days (pH 4); 0, 0.25, 1, 2, 4, 8, 18 and 35 days (pH 7) and 0, 0.25, 1, 3, 7, 17 and 34 days (pH 9). At each sampling interval, the radioactivity in duplicate samples was determined by LSC. The transformation products were determined by reversed-phase HPLC/radiodetection. Identification of transformation products was performed by HPLC-MS(/MS) as well as by HPLC co-chromatography or profile comparison.

 

Material balances (mean values) ranged from 79.4 to 101.3% AR for all tests. The amount of dissolved test item was determined by LSC and the coverage of all transformation products by HPLC was determined using the quotient of the total peak area detected in HPLC divided by the amount of radioactivity measured in the test solutions. This quotient was more or less constant for pH 7 and pH 9 samples throughout the entire incubation period which indicates a complete dissolution of the radioactivity from DAT-0 (0 days after treatment) onwards. In case of the pH 4 test series, the dissolution of the radioactivity was slower (about 80% dissolution at DAT-0). In these samples the radioactivity was completely dissolved from about DAT-1/DAT-5 onwards.

 

The test item Propineb could not be detected in the test solutions due to its insolubility and fast degradation. In all test conditions degradation was accompanied by the formation of six fractions in radio-HPLC > 10% AR.

 

The main transformation product in all tests was PTU (propylene-thiourea) which accounted for up to 95.5% AR (DAT-5, pH 7, 50 °C). The second terminal transformation product PU (propylene-urea) was predominantly formed in pH 9 samples and reached up to 17.3% AR (DAT-1, pH 9, 50 °C). Investigations were performed under the four other peaks > 10% AR, these fractions were regarded as transient in the hydrolysis study as a decrease of these fractions during the course of the study was observed predominantly in pH 7 and pH 9 samples.

 

Overall, the degradation of the transient transformation products summarized  was fast at pH 7 and pH 9, while in the pH 4 samples, their amounts as well as the amounts of PTU remained on a low level from DAT-1 or DAT-2 onwards. Since the total amount of radioactivity represented transformation products already for the first sampling interval (about 0.5 hours after application), it is concluded that the DT50 is less than 0.5 hours at pH 4, pH 7 and pH 9 for all temperatures.

Description of key information

The hydrolysis of radiolabeled [propane-1-¹⁴C]Propineb was studied in the dark at 50, 25 and 20 °C in sterile aqueous buffer solutions at pH 4 (0.01 M acetate buffer), pH 7 (0.01 M TRIS buffer), and pH 9 (0.01 M borate buffer) for a maximum of 35 days. Propineb is not stable in aqueous solution and shows a spontaneous reaction. Since the total amount of radioactivity represented transformation products already for the first sampling interval (about 0.5 hours after application), it might be concluded that the DT50 is less than 0.5 hours at pH 4, pH 7 and pH 9 for all temperatures.

Key value for chemical safety assessment

Half-life for hydrolysis:

0.5 h

at the temperature of:

20 °C