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Environmental fate & pathways

Phototransformation in water

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Reference
Endpoint:
phototransformation in water
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Acceptable, well-documented publication which meets basic scientific principles (also assessed by OECD)
Study type:
direct photolysis
Qualifier:
no guideline followed
Principles of method if other than guideline:
Direct UV irradiation of an aqueous solution with a low pressure mercury lamp
GLP compliance:
no
Specific details on test material used for the study:
Commercial TPP purified by zone refining; purity checked by GC.
Radiolabelling:
no
Analytical method:
gas chromatography
Details on sampling:
A 100mL subsample of the solution was adjusted to pH3 with HCl, 50mL of this sample was saturated with NaCl and extracted with dichloromethane. This extract was dried over anhydrous sodium sulphate and the dichloromethane was then concentrated until almost dry. The residue was reconstituted in acetone and analysed by GC. A further 50mL aliquot was taken and potassium carbonate added followed by acetic anhydride. The solution was thoroughly mixed and the acetylated compounds were extracted with hexane. The hexane was analysed by GC or GC-MS.
Buffers:
Purified water was used adjusted to the desired pH with either HCl or NaOH.
Light source:
other: low pressure 15W mercury lamp
Light spectrum: wavelength in nm:
254
Details on light source:
A Taika Kogyo Model HLV-A reactor equipped with a 15W low pressure mercury lamp.
Details on test conditions:
A given amount of triphenyl phosphate was placed in a 200 mL flask and 100 mL of purified water added. After ultrasonication for 1 hour the solution was placed in the reactor and 1900 mL of purified water added with stirring. After 30 minutes of stirring 200 mL of solution was taken as a reference solution and that remaing adjusted to a given pH.
Initial conc. measured:
0.1 mg/L
Reference substance:
no
Dark controls:
no
Test condition:
Direct photolysis
Transformation products:
yes
No.:
#1
No.:
#2
Disappearance of 0.1 mg/L TPP at pH3 and pH10 resp. caused by irradiation 
occurred rapidly. Pseudo 1st order rate constant was >40/hour (half-life 1.04 
minutes) at both pH levels.
TPP degradation without pH adjustment at pH 3.4 after 6 h irradiation:
100 % TPP degraded, 60 % of theoretical phosphate found, no phenol found.
TPP degradation with initial pH 12 after 6 h irradiation:
100 % TPP degraded, 60 % of theoretical phosphate found, 9 % of theoretical phenol found (23% after 3h). The produced phenol was further decomposed by irradiation.
Degradation products di- and monophenyl phosphate were not determined in either of the tests.
Degradation at alkaline pH may involve the hydrolysis with NaOH.
Validity criteria fulfilled:
not specified
Conclusions:
There was rapid degradation of TPP by irradiation with a half life of 1.04 minutes at both pH3 and 10
Executive summary:

A direct photolysis study was conducted for TPP. Indicating a rapid degradation of TPP by irradiation with a half life of 1.04 minutes at both pH 3 and 10.

Under acidic conditions no phenol was found after 6h of irradiation which suggests that the degradation of the benzene ring occurs faster than the production of phenols. Under basic conditions a certain amount of phenol is found, indicating faster production, however, this may be due to alkaline hydrolysis.  

Description of key information

A direct photolysis study was performed in which TPP is rapidly degraded(within 1.04 min.) when irradiated at 254 nm at pH 3 and pH 10.

Key value for chemical safety assessment

Half-life in water:
1.04 min

Additional information

Degradation products di- and monophenyl phosphate were not determined in either of the 
test. Phenol was found when TPP was irradiated at pH 10 but not at pH 3.  
Degradation at alkaline pH may involve the hydrolysis with NaOH.