1-nitroguanidine

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

Study period:

1982

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

documentation insufficient for assessment

Study type:

direct photolysis

Principles of method if other than guideline:

Solutions of nitroguanidine in distilled water at pH 6.0, 100 ppm in concentration and 2.5 cm deep, were stirred in beakers under a germicidal UV lamp (Sylvania G15T8). Samples were withdrawn periodically and determination by HPLC.

GLP compliance:

not specified

Specific details on test material used for the study:

Test substance supplier Randford Army Ammunition Plant, Radford

Radiolabelling:

no

Analytical method:

high-performance liquid chromatography

Light source:

other: UV lamp

Duration:

60 min

Initial conc. measured:

100 other: ppm

% Degr.:

ca. 50

Sampling time:

60 min

Test condition:

pH 6.0, 100 ppm

Transformation products:

yes

No.:

#1

No.:

#2

Validity criteria fulfilled:

not applicable

Conclusions:

After approximately 60 min. 50 % of nitroguanidine were decomposed, indicating, that nitroguanidine is sensitive to UV light.

Executive summary:

Solutions of nitroguanidine in distilled water at pH 6.0, 100 ppm in concentration and 2.5 cm deep, were stirred in beakers under a germicidal UV lamp (Sylvania G15T8). Samples were withdrawn periodically and determination by HPLC. After approximately 60 min. 50 % of nitroguanidine were decomposed, indicating, that nitroguanidine is sensitive to UV light. Degradation products were nitrosoguanidine and cyanamide.

Reference 2

Endpoint:

phototransformation in water

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

1982

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

secondary literature

Justification for type of information:

This is a review of environmental fate, although comprehensive and useful for extracting physico-chemical data and general fate information, it is not a report of a single laboratory.

Reason / purpose for cross-reference:

reference to same study

Study type:

not specified

Principles of method if other than guideline:

No data

GLP compliance:

not specified

Specific details on test material used for the study:

Test substance supplier not specified

Radiolabelling:

not specified

Light source:

not specified

Transformation products:

not measured

Validity criteria fulfilled:

not specified

Conclusions:

Nitroguanidine is sensitive to shortwave ultraviolet light.

Executive summary:

Studies by Bissett and Levasseur (cited in Kenyon, 1982) on ultraviolet adsorption reveal that nitroguanidine in aqueous solution shows only one band at pH 2-12. The λ_maxof this band is 264 nm (E_max= 13000), which decreases under more alkaline conditions as a new band at λ_max246 nm appears. Bissett and Lavsseur (cited in Kenyon, 1982) state that this shift in adsorption is indicative of a shift from structure (A) to structure (B) (see attached figure 1). A recent study by Kaplan et al., 1982 (cited in Kenyon, 1982), looked at ultraviolet sensitivity of 100 ppm nitroguanidine in distilled H₂O at pH 6.0, in containers 2.5 cm deep. Analysis indicated that nitroguanidine is sensitive to shortwave ultraviolet light. No photolysis rates were given, and tests were not performed in natural waters, which have been shown to contain humic substances enhancing photolysis of other explosive compounds.

Reference 3

Endpoint:

phototransformation in water

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

1987

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Study type:

direct photolysis

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 316 (Phototransformation of Chemicals in Water - Direct Photolysis)

Principles of method if other than guideline:

Photolysis experiments were performed with 50 µM aqueous nitroguanidine solutions in sunlight in quartz tubes (1cm o.d.) held on a rack at 30° from the horizon, the loss of nitroguanidine was monitored by HPLC. The variation in sunlight flux was monitored using p-nitroacetophenone/pyridine (PNAP/PYR) actinometers. At each time point, actinometer and NQ tubes were removed and stored at Additional photoproduct studies were performed in the laboratory using a 300 Watt xenon lamp and samples were irradiated in borsilicate glass tubes to remove light below 290 nm. The filtered lamp has a spectral output closely approximating that of sunlight and an intensity at 300 to 400 nm about three times that of noon summer sunlight at 38 °N, as determined by PNAP/PYR actinometry. Stationary tubes were exposed 30 cm from the lamp and kept at room temperature (25 +/- 2 °C) by use of a fan. Samples were placed in the dark until analysis for NQ, hydroxguanidine, guanidine and cyanamide by reversed phase, paired-ion chromatography.

GLP compliance:

not specified

Specific details on test material used for the study:

Test substance supplier: Aldrich Chemical Co
Water content 25 %

Radiolabelling:

no

Analytical method:

high-performance liquid chromatography

other: reversed phase, paired-ion chromatography

Light source:

other: 1. Sunlight; 2. Xenon lamp

Quantum yield (for direct photolysis):

0.01

DT50:

>= 0.6 - <= 2.3 d

Test condition:

surface water half-lifes at 40 °N ranging from summer to winter

Transformation products:

yes

No.:

#1

No.:

#2

No.:

#3

Validity criteria fulfilled:

not applicable

Conclusions:

In surface waters nitroguanidine is subject to degradation by photolysis.

Executive summary:

The environmental fate of nitroguanidine in surface waters is dominated by photolysis with surface half-lives at 40 °N range from 0.6 d in summer to 2.3 d in winter. The quantum yield ( number of times a specific event occurs per photon absorbed by the system) for nitroguanidine photolysis was measured to be 0.01 molecules decomposed/photons absorbed. Nitroguanidine is initially photolyzed to nitrite and hydroxyguanidine; nitrite is photochemically converted to nitrate and hydroxyguanidine undrgoes sensitized photolysis to unknown products. The photooxidation of nitrite is assisted by organic material in a process not involving H₂O₂ or singlet oxygen.

Reference 4

Endpoint:

phototransformation in water

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

1984

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

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

Study type:

direct photolysis

Qualifier:

no guideline followed

Principles of method if other than guideline:

Nitroguanidine solution was prepared within an hour before use. The pH was adjusted with hydrochloric acid or sodium hydroxide. In indicated experiments, test solutions were buffered with 0.01 M sodium phosphate or sodium borate to maintain pH values of 7 and 11, respectively. Samples were removed from the reactor column at timed intervals. Each sample bottle contained sodium thiosulfate to quench oxidants which may have been present in the sample.
The reactor column consists of a stainless steel cylinder, 78 inches high and 6.6 inches in diameter. It contains a sintered stainless steel gas sparger with a mean pore size of 5 micrometers, which is located approx. 2 inches above the base of the reactor. An 80-watt lamp encased in a 1 inch quarts sleeve runs vertically through the center of the column. The lamp emits UV light at a wavelength of 253.7 nm. Mixing of reactor contents was achived by recirculating wastewater at a flow rate of 2 gpm.
Nitroguanidine solutions were exposed to UV light and nitroguanidine concentrations were measured.

GLP compliance:

not specified

Specific details on test material used for the study:

Test substance supplier is not specified

Radiolabelling:

no

Analytical method:

high-performance liquid chromatography

other: IC

Light source:

other: 80-watt lamp

Light spectrum: wavelength in nm:

253.7

Type of sensitiser:

O3 (ozone)

Concentration of sensitiser:

0.1 other: % solution

Type of sensitiser:

other: hydrogen peroxide

Concentration of sensitiser:

0.1 other: % solution

Duration:

60 min

Temp.:

20 °C

Initial conc. measured:

100 mg/L

Reference substance:

not specified

Dark controls:

not specified

Key result

% Degr.:

60

Sampling time:

1 h

Test condition:

UV radiation, ambient temperature, pH 7

DT50:

50 min

Test condition:

initial concentration: 100 mg/l; without ozone or hydrogen peroxide; ambient temperature

DT50:

ca. 15 min

Test condition:

initial concentration: 20 mg/l; without ozone or hydrogen peroxide; ambient temperature

Transformation products:

yes

No.:

#1

No.:

#2

No.:

#3

No.:

#4

No.:

#5

No.:

#6

No.:

#7

No.:

#8

No.:

#9

No.:

#10

No.:

#11

- The use of ozone or hydrogen peroxide in conjunction with UV light did not enhance nitroguanidine destruction.

- Calculated pseudo-first order reaction rate constants show that ozone application actually decreased the rate of nitroguanidine destruction.

- The rate of nitroguanidine degradation was not dependent upon pH.

- Data from initial studies on nitroguanidine degradation by UV light produced a half-life of approx. 50 min. Continuing experiments conducted over 4 to 5 half-lives showed a dramatic disappearance of nitroguanidine when the reactor solution concentration reached 20 mg/L. A straight-line plot on semi-log paper no longer existed, indicating that the destruction of nitroguanidine was not pseudo-first order over the entire concentration range. The slopes were -0.979 mg/(L*min) and -4.460 mg/(L*min) for initial nitroguanidine concentrations of 100 mg/L and 20 mg/L, respectively.

- At least 50 % of nitroguanidine-nitrogen could not be recovered during UV treatment at neutral or acidic pH values.

- Nonrecoverable nitrogen was as high as 80 to 85 % when nitroguanidine solutions were treated at pH 11.

Validity criteria fulfilled:

not applicable

Conclusions:

Nitroguanidine is sensitive to UV radiation. The end products of UV photolysis are dependent upon the wastewater pH.

Executive summary:

Nitroguanidine was degraded with UV radiation. The end products of UV photolysis are dependent upon the wastewater pH. At pH values ranging between 3 and 10, guanidine and nitrate-nitrogen were produced, accounting for approx. 40 percent of the total nitrogen content. An additional 10 percent of the total nitrogen was recovered as identifiable compounds at low concentrations. The remaining 50 % of nitroguanidine-nitrogen were not recovered. At pH values greater than 11, no guanidine was formed during photolysis of nitroguanidine. Under these conditions, greater than 80 % of the initial nitroguanidine-nitrogen at acidic and alkaline pH values was associated with the production of guanidine. In summation, the rate of UV photolysis of nitroguanidine was independent of pH, but the production of guanidine occurred only below pH 11. Neither hydrogen peroxide nor ozone was capable of degrading nitroguanidine or guanidine. The use of hydrogen peroxide or ozone in conjunction with UV light did not increase the rate of nitroguanidine destruction or the apparent distribution of identifiable products. Guanidine persisted throughout all tests. Therefore, guanidine formation from photolysis of nitroguanidine must be considered when effluent limits are set for both nitroguanidine and guanidine.

Description of key information

Photolysis experiments with nitroguanidine were conducted by exposing nitroguanidine solutions either to direct sunlight (Spanggord et al., 1987 & Haag et al., 1990), or to UV radiation of lamps (Kaplan et al., 1982; Noss & Chyrek, 1984; Spanggord et al., 1987 & Haag et al., 1990). Degradation of nitroguanidine was monitored by test material analysis (HPLC) in the test’s solutions after periodic intervals. Nitroguanidine is quickly photolyzed. The quantum yield for nitroguanidine photolyses was measured to be 0.01. According to Haag et al., 1990 & Spanggord et al., 1987, Nitroguanidine is initially photolyzed to nitrite and hydroxyguanidine; nitrite is photochemically converted to nitrate and hydroxyguanidine.

Key value for chemical safety assessment

Half-life in water:

2.3 d

Additional information

Studies by Bissett and Levasseur (cited in Kenyon, 1982) on ultraviolet adsorption reveal that nitroguanidine in aqueous solution shows only one band at pH 2-12. The λ_max of this band is 264 nm (E_max= 13000), which decreases under more alkaline conditions as a new band at λ_max 246 nm appears. Bissett and Lavsseur (cited in Kenyon, 1982) state that this shift in adsorption is indicative of a shift between two tautomeric forms.

The study by Kaplan et al., 1982, looked at ultraviolet sensitivity of 100 ppm nitroguanidine in distilled H₂O at pH 6.0, in containers 2.5 cm deep. Analysis indicated that nitroguanidine is sensitive to shortwave ultraviolet light. Degradation products were nitrosoguanidine and cyanamide. No photolysis rates were given, and tests were not performed in natural waters, which have been shown to contain humic substances enhancing photolysis of other explosive compounds.

Haag et al., 1990 & Spanggord et al., 1987 estimated the half-live range for nitroguanidine in surface waters at 40 °N from 0.6 d in summer to 2.3 d in winter. The quantum yield for nitroguanidine photolyses was measured to be 0.01. According to Haag et al., 1990 & Spanggord et al., 1987, Nitroguanidine is initially photolyzed to nitrite and hydroxyguanidine; nitrite is photochemically converted to nitrate and hydroxyguanidine undergoes sensitized photolysis to unknown products. The photooxidation of nitrite is assisted by organic material in a process not involving H₂O₂ or singlet oxygen.

Noss & Chyrek, 1984 could demonstrate that the end products of UV photolysis are dependent upon the wastewater pH. At pH values ranging between 3 and 10, guanidine and nitrate-nitrogen were produced, accounting for approx. 40 percent of the total nitrogen content. An additional 10 percent of the total nitrogen was recovered as identifiable compounds at low concentrations. The remaining 50 % of nitroguanidine-nitrogen were not recovered.

At pH values greater than 11, no guanidine was formed during photolysis of nitroguanidine. Under these conditions, greater than 80 % of the initial nitroguanidine-nitrogen at acidic and alkaline pH values was associated with the production of guanidine. In summation, the rate of UV photolysis of nitroguanidine was independent of pH, but the production of guanidine occurred only below pH 11.