N-1-naphthylaniline

Phototransformation in water

Link to relevant study record(s)

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

Study type:

direct photolysis

Qualifier:

no guideline followed

Principles of method if other than guideline:

following recommendations of US EPA

GLP compliance:

not specified

Radiolabelling:

no

Analytical method:

high-performance liquid chromatography

Details on sampling:

- Sampling intervals for the parent/transformation products: 0, 10, 21, 31 and 46 min.; 0, 2, 4, 6, 8, 11, 15 and 20 min

Light source:

sunlight

Light spectrum: wavelength in nm:

300

Details on light source:

- Emission wavelength spectrum: 300 nm
- Other: Rayonett Model RMR-400-mini photochemical reactor

Details on test conditions:

TEST SYSTEM
- Type, material and volume of test apparatus/vessels: cylindrical quartz tubes (1.3 cm ID), sealed with parafilm to prevent evaporation
- If no traps were used, type of test system: closed
- Indication of test material adsorbing to the walls of test apparatus: no


TEST MEDIUM
- Volume used/treatment. 5 mL aliquots of an aqueous solution of PNA

Duration:

46 min

Initial conc. measured:

1 350 other: ppb

Reference substance:

no

Dark controls:

not specified

% Degr.:

71

Sampling time:

10 min

% Degr.:

89.1

Sampling time:

21 min

% Degr.:

94.3

Sampling time:

31 min

% Degr.:

98

Sampling time:

46 min

Rate constant (for indirect photolysis):

>= 0.008 - <= 0.121 other: /min

DT50:

>= 5.7 - <= 8.4 min

Transformation products:

yes

No.:

#1

Details on results:

TEST CONDITIONS
- pH, sterility, temperature, and other experimental conditions maintained throughout the study: No


MAJOR TRANSFORMATION PRODUCTS (distinguish between dark and irradiated samples)
- Range of maximum concentrations in % of the applied amount and day(s) of incubation when observed: 79% after 12 min. of irradiation, 81% after 35 min. of irradiation

First experiment: 98% degradation after 46 min (71% after 10 min, 89.1% after 21 min, 94.3% after 31 min). Second experiment: 91% degradation after 20 min (7.75% after 2 min, 35.3% after 4 min, 58.5% after 6 min, 66.9% after 8 min, 74.7% after 11 min, 83.4% after 15 min).

An additional experiment showed that degradation proceeds to a much greater extent in a deoxygenated medium (before photolysis: 1.38 ppm, after photolysis: 0.85 ppm, degasssed after photolysis: 0.054 ppm).

The major product has an adsorption maximum at approx. 260 nm. It was shown that this photoproduct of PNA resists further photodegradation as the percent conversion of PNA to product remains constant at approx. 80% after 12 min of photolysis. A further experiment showed 30% photodegradation after 24 h and very little degradation after 5 h with sensitization by 1.9 ppm humic acid.

Description of key information

Photodegradation in water is a relevant route for degradation of the substance in the environment.

Key value for chemical safety assessment

Half-life in water:

8 min

Additional information

In the key study, the photodegradation of N-phenyl-1-naphtylamine in an aqueous solution was studied under natural sunlight as well as under laboratory conditions (Sikka et al. 1981). Photodegradation in sunlight is rapid and proceeds with a half-life of 5 to 8 min. The rate is, however, influenced by oxygen, and considerably enhanced rates are obtained in deoxygenated solutions. Photodegradation in aerated solutions appears to lead to one primary product which is relatively photostable and inert to sensitization by humic acid. Preliminary spectral data indicate that it may be the aniline adduct of 1,3-naphthoquinone.