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Phototransformation in water

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Endpoint:
phototransformation in water
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Study has been published in a peer-reviewed journal fulfilling international scientific standards
Study type:
indirect photolysis
Qualifier:
no guideline followed
Principles of method if other than guideline:
Investigation of photochemical degradation of Benzotriazole in aqueous solution by using a diode array spectrophotometer to measure the total absorption at 254 nm.
GLP compliance:
no
Radiolabelling:
no
Analytical method:
high-performance liquid chromatography
Buffers:
- pH: 3 - 11
- Type and final molarity of buffer: 0.1 mol/L phosphate buffer
- Composition of buffer:
Light source:
other: low-pressure lamp (Helios Italquartz)
Light spectrum: wavelength in nm:
254
Details on light source:
- Emission wavelength spectrum: 254 nm monochromatic
- Filters used and their purpose:
- Light intensity at sample and area irradiated:
- Relative light intensity based on intensity of sunlight:
- Duration of light/darkness:
- Other:
Details on test conditions:
TEST SYSTEM
- Type, material and volume of test apparatus/vessels:
- Sterilisation method:
- Measures to saturate with oxygen:
- Details on test procedure for unstable compounds:
- Details of traps for volatile, if any:
- If no traps were used, type of test system: [closed/open]
- Indication of test material adsorbing to the walls of test apparatus: [yes: /no]

TEST MEDIUM
- Volume used/treatment
- Kind and purity of water: HPLC water
- Source of natural water (if applicable) in terms of geographical location, site characteristics and date of collection: not applicable
- Preparation of test medium: 4 cm3 H3PO4 (85%), 50 cm3 methanol, 1 dm3 water
- Renewal of test solution: no renewal
- Identity and concentration of co-solvent: not applicable
- Concentration of solubilising agent: not applicable

REPLICATION
- No. of replicates (dark):
- No. of replicates (irradiated):

OTHER
Reference substance:
no
Dark controls:
no
Parameter:
other: epsilon 254 nm
Value:
5 737 other: cm*dm3*mol-1
Remarks:
pH 3.0
Parameter:
other: epsilon 254 nm
Value:
5 737 other: cm*dm3*mol-1
Remarks:
pH 5.0
Parameter:
other: epsilon 254 nm
Value:
5 692 other: cm*dm3*mol-1
Remarks:
pH 7.0
Parameter:
other: epsilon 254 nm
Value:
4 390 other: cm*dm3*mol-1
Remarks:
pH 9.0
Parameter:
other: epsilon 254 nm
Value:
3 844 other: cm*dm3*mol-1
Remarks:
pH 11.0
Transformation products:
not measured

During the tests development of NOx or ammonia ions has not been detected. In addition, no other major peaks have been detected in the HPLC chromatograms. Otherwise the solutions have changed theirs colours showing a very fine dark-brown precipitate which has not been analysed but has been assumed to be polymerisation products of Benzotriazole.

Validity criteria fulfilled:
not applicable
Conclusions:
Under acidic and neutral pH conditions Benzotriazole can be effectively degraded by UV light.
Executive summary:

The reported observations in this publication at different pH values have shown a decreasing degradation rate of dissolved Benzotriazole in aqueous solutions with increasing pH value. Since Benzotriazole is a weak acid with a pKa value of about 8.3 the used pH range in the experiments covers both forms of the substance, ionic and non-ionic. Based on the results it can be assumed that the ionic form of Benzotriazole is much less reactive than the non-ionic form.

Endpoint:
phototransformation in water
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Study has been published in a peer-reviewed journal fulfilling international scientific standards
Study type:
indirect photolysis
Qualifier:
no guideline followed
Principles of method if other than guideline:
Different concentrations of test item in distilled water at different pH values has been illuminated with UV light and changes in the absorbance have been detected with a photospectrometer. UV dose was varied by retention time of solutions in flow-through chamber of UV reactor. Additionally, transformation products have been analysed by GC/MS.
GLP compliance:
no
Radiolabelling:
no
Analytical method:
gas chromatography
other: photospectrometer
Details on sampling:
- Sampling intervals for the parent/transformation products:
- Sampling method:
- Sampling methods for the volatile compounds, if any:
- Sampling intervals/times for pH measurements:
- Sampling intervals/times for sterility check:
- Sample storage conditions before analysis:
- Other observation, if any (e.g.: precipitation, color change etc.):
Light source:
other: UV unit Berson Inline 20 (Birger Christensen, Norway)
Light spectrum: wavelength in nm:
> 240 - < 300
Details on light source:
- Emission wavelength spectrum: 270 ± 30 nm
- Filters used and their purpose:
- Light intensity at sample and area irradiated: 34 - 2500 mWs/cm2
- Relative light intensity based on intensity of sunlight:
- Duration of light/darkness:
- Other:
Details on test conditions:
TEST SYSTEM
- Type, material and volume of test apparatus/vessels:
- Sterilisation method:
- Measures to saturate with oxygen:
- Details on test procedure for unstable compounds:
- Details of traps for volatile, if any:
- If no traps were used, type of test system: [closed/open]
- Indication of test material adsorbing to the walls of test apparatus: [yes: /no]

TEST MEDIUM
- Volume used/treatment
- Kind and purity of water:
- Source of natural water (if applicable) in terms of geographical location, site characteristics and date of collection:
- Preparation of test medium:
- Renewal of test solution:
- Identity and concentration of co-solvent:
- Concentration of solubilising agent:

REPLICATION
- No. of replicates (dark):
- No. of replicates (irradiated):

OTHER
Reference substance:
no
Dark controls:
no
Transformation products:
yes
No.:
#1
No.:
#2
No.:
#3

water flow (L/min)

pH

UV dose (mWs/cm2)

Benzotriazole (mg/L)

reduction (%)

In

Out

1.5

6.7

2500

0

0

-

1.4

6.8

1070

7.6

0.87

89

5.8

7.0

320

4.5

1.6

64

46

7.0

34

5.1

4.2

18

1.4

7.8

860

7.3

5.9

19

6

7.6

280

4.5

3.9

13

40

7.6

36

6.4

4.9

23

Table 1. UV reduction of Benzotriazole

Reduced degradation of Benzotriazole at pH 8 has been based on decreased UV absorbance of the ionic form of the substance. As the solutions have changed their colours incomplete mineralisation during the process has been assumed. By analysis as mentioned in field "Any other information on materials and methods incl. tables" aniline (< 1 %), phenazine (10 -20 %) and an unknown compound (0.5 -16 %) have been observed. Based on the mass spectra of the unknown compound an oxidation product of phenazine, 11H-dibenzo[b,e][1,4]dioxepin-11-one, can be assumed.

Validity criteria fulfilled:
not applicable
Conclusions:
Dissolved Benzotriazole in aqueous solution has not been fully mineralised by UV light. Transformation products have been identified by GC/MS-EI showing an enhanced biodegradability.
Executive summary:

In the available publication degradation of Benzotriazole in aqueous solution by UV irridiation has been examined. At acidic and neutral pH values reduction up to 65 % has been archieved at low dose of UV irridiation (320 mWs/cm2) and up to 90 % reduction at high dose (1070 mWs/cm2). Degradation process could be described by first order kinetics. At higher pH values (> pH 8) only reduced degradation has been observed due to the ionic character of Benzotriazole (pKa 8.6) and the associated reduced UV absorbance.

Benzotriazole has not been completely mineralised during the process. In addition to aniline and phenazine a third transformation product has been observed by HPLC. The results have given indications on a high-molecular metabolite, potentially 11H-dibenzo[b,e][1,4]dioxepin-11 -one, a oxidation product of phenazine.

Description of key information

Key value for chemical safety assessment

Additional information

Available publications have given clear indication of relevant photodegradation processes of 1H-Benzotriazole in aqueous solutions under acidic and neutral pH conditions. Under basic conditions, the ionic form of 1H-Benzotriatole has been dominant showing a reduced reactivity to UV light.

Hem et al. have identified aniline, phenazine and supposable an oxidation product of phenazine as relevant transformation products. Based on these findings it can be assumed that photodegradation in water enhances the detoxification and biodegradability of 1H-Benzotriazole.