Benzotriazole

Phototransformation in water

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

phototransformation in water

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

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 was not detected. In addition, no other major peaks were detected in the HPLC chromatograms. Otherwise the solutions had changed theirs colours showing a very fine dark-brown precipitate which was not analysed, but was assumed to be polymerisation products of 1H-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 show 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 salt of Benzotriazole is less reactive than the non-ionic form.

Reference 2

Endpoint:

phototransformation in water

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

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/cm^2)	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 is based on decreased UV absorbance of the ionic form of the substance. As the solutions have changed their colours, incomplete mineralisation during the process was 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 %) were 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 1H-Benzotriazole in aqueous solution was not fully mineralised by UV light. Transformation products were identified by GC/MS-EI showing an enhanced potential for biodegradability.

Executive summary:

In the available publication degradation of 1H-Benzotriazole in aqueous solution by UV irridiation was examined. At acidic and neutral pH values reduction up to 65 % was 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 was observed due to the formation of Benzotriazolate and the associated reduced UV absorbance.

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

Description of key information

The photolysis of 1H-Benzotriazole in water depends to a large extent on the environmental conditions (e.g. pH, presence of DOM, sunlight etc). Thus, no reliable value was identified and used in the assessment.

Additional information

Available publications gave 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 was dominant showing a reduced reactivity to UV light.

Hem et al. 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.

In newer studies Bianco et al investigated the phototransformation of Benzotriazole in dependence of the pH value and in presence of sensitizers. In the experiments a half-life of some days/weeks to months was predicted under environmental conditions. The ionized Benzotriazolate showed a lower susceptibility to photolysis. In addition, Bianco proposed intermediates with up to three hydroxyl groups on the C6 ring.

Janssen et al. conducted laboratory experiments with artificial sunlight and UVA/UVB lamps in nanopure water as well as in presence of natural DOMs (Suwannee River Fulvic Acid and Waskish Peat Organic Matter). Findings indicted that Benzotriazole is faster photolyzed in the presence of DOMs. Under laboratory conditions a half-life of 1.4 days (with DOM) and 1.8 days (without DOM) was determined.

Weidauer et at. investigated the photolytic behaviour of Benzotriazole with an artificial sun simulator in aqueous solution and in presence of DOM (Suwannee River fulvic acid). The results indicated a half-life at summer sunny day conditions of about nine days. In additional analysis several transformation products were identified, and a potential pathway was proposed (in absence of DOM). Furthermore, the observations indicated potential reactions of Benzotriazole with DOMs after the initial photolytic step forming unknown nitrogenous organic molecules.

Further studies by Benitez et al and Borowska et al. also investigated the direct and indirect photolysis of Benzotriazole in laboratory studies. Benitez used t-Butanol as sensitizer for indirect photolysis experiments at pH 3, 5, 7, and 9. Using monochromatic UV light at 254 nm Benzotriazole was quickly transformed (DT100 < 40 min). Based on the results of a HPLC-QTOF-MS analysis the authors proposed a reaction pathway via nitrogen elimination and hydroxylation of the triple-N-ring forming 2-Aminophenol. Borowska used a medium-pressure mercury lamp in the study, and investigated the photochemical processes at pH 5, 7, and 9 in aqueous solution and filtered wastewater taken from a STP after biological treatment in a membrane bioreactor. Independent of the pH value Benzotriazole was quicky removed (< 60 min), but the results showed a slower removal rate in the wastewater. The findings in the analytical measurements indicated a degradation pathway via hydroxylation of the C6 ring.

 

Benitez et al., Photolysis of model emerging contaminants in ultra-pure water: Kinetics, by-products formation and degradation pathways, Wat. Res. 47 (2013 870-880.
Borowska et al., Oxidation of benzotriazole and benzothiazole in photochemical processes: Kinetics and formation of transformation products, Chemical Engineering Journal 304 (2016) 852–863.