Laboratory samples of uns-dimethylhydrazine (UDMH) fuel/oxidizer (nitrogen dioxide) non-combustion reaction products (UFORP) were prepared using a unique permeation tube technology. Also, a synthetic UFORP was prepared from UDMH, N-nitrosodimethylamine (NDMA), dimethylammonium nitrate, sodium nitrite and purified water. The evaporation rate of UFORP and synthetic UFORP was determined under space vacuum (approx 10(exp -3) Torr) at -40 ?C and 0 ?C. The material remaining was analyzed and showed that the UFORP weight and NDMA concentration decreased over time; however, NDMA had not completely evaporated. Over 85% of the weight was removed by subjecting the UFORP to 10(-3) Torr for 7 hours at -40 ?C and 4 hours at 0 ?C. A mixture of dimethylammonium nitrate and sodium nitrite formed NDMA at a rapid rate in a moist air environment. A sample of UFORP residue was analyzed for formation of NDMA under various conditions. It was found that NDMA was not formed unless nitrite was added

Baker, David L.

Buchanan, Vanessa D.

Dee, Louis A.

NASA Technical Reports Server

EVAPORATION RATE STUDY AND NDMA FORMATION FROM 
UDMH/NO2 REACTION PRODUCTS∗ 
 
Vanessa D. Buchanan 
Louis A. Dee 
Honeywell Technology Solutions, Inc. 
NASA Johnson Space Center 
White Sands Test Facility 
Las Cruces, New Mexico 
 
David L. Baker  
NASA Johnson Space Center 
White Sands Test Facility 
Las Cruces, New Mexico 
 
 
ABSTRACT 
 
Laboratory samples of uns-dimethylhydrazine (UDMH) fuel/oxidizer (nitrogen dioxide) non-
combustion reaction products (UFORP) were prepared using a unique permeation tube technology.  Also, 
a synthetic UFORP was prepared from UDMH, N-nitrosodimethylamine (NDMA), dimethylammonium 
nitrate, sodium nitrite and purified water.  The evaporation rate of UFORP and synthetic UFORP was 
determined under space vacuum (~10-3 Torr) at -40 °C and 0 °C.  The material remaining was analyzed 
and showed that the UFORP weight and NDMA concentration decreased over time; however, NDMA had 
not completely evaporated.  Over 85% of the weight was removed by subjecting the UFORP to 10-3 Torr 
for 7 hours at –40 °C and 4 hours at 0 °C.  A mixture of dimethylammonium nitrate and sodium nitrite 
formed NDMA at a rapid rate in a moist air environment.  A sample of UFORP residue was analyzed for 
formation of NDMA under various conditions.  It was found that NDMA was not formed unless nitrite was 
added.   
 
INTRODUCTION AND OBJECTIVE 
 
The International Space Station (ISS) Program Office requested testing of contamination being 
deposited on the surface of the service module.  This contamination is a reaction product of uns-
dimethylhydrazine (UDMH)/nitrogen dioxide.  Astronauts may inadvertently bring this UDMH fuel/oxidizer 
reaction product (UFORP) into the airlock after an extravehicular activity (EVA).  Earlier work established 
that a major ingredient of the UFORP was N-nitrosodimethylamine (NDMA), a potent carcinogen.1  This 
laboratory was tasked to (1) determine the evaporation rate of the volatile components in a simulated 
space vacuum at selected temperatures and (2) to determine if NDMA is formed upon exposure of the 
nonvolatile UFORP residue to moist air.  NDMA has been known to form in aqueous solutions containing 
dimethylamine and nitrite ion.2  This data will allow Johnson Space Center (JSC) and Boeing to determine 
time requirements for evaporation of the volatile UFORP components and to assess the hazard potential 
if nonvolatile UFORP components are introduced into the airlock.  
 
EXPERIMENTAL 
 
PREPARATION OF UFORP 
 
The UFORP was prepared by combining vapor streams from permeation tubes filled with liquid uns-
dimethylhydrazine (UDMH) and oxidizer (N2O4) in a centrifuge tube chilled to 0 °C in accordance with the 
procedure described in earlier work.1  UFORP prepared this way is a yellowish-orange liquid as shown in 
Figure 1, and consists of NDMA (approximately 0.8%) and other organic compounds.  
                                                     
∗Approved for public release, distribution is unlimited. 
https://ntrs.nasa.gov/search.jsp?R=20120002683 2019-08-30T19:20:38+00:00Z
  
 
Figure 1.  UFORP residue before exposure to 10-3 Torr (0.5075g) 
 
 
PREPARATION OF SYNTHETIC UFORP 
 
Synthetic UFORP was prepared by mixing 2.5 mL of neat UDMH, 2.0 mL of neat NDMA, 0.43 g of 
dimethylammonium nitrate, 0.33 g sodium nitrite and 0.8 mL of purified water.  Not all of the nitrate and 
nitrite salts were in solution. 
 
PREPARATION OF DIMETHYLAMMONIUM NITRATE/NITRITE 
 
Dimethylammonium nitrate was formed using an anion exchange resin (J. T. Baker, IONAC A-554 Cl- 
Form, Type II Beads (16-50 Mesh)).  Aqueous sodium nitrate was first passed through the column to 
convert the resin from the chloride to the nitrate form.  Then aqueous dimethylammonium chloride 
(Aldrich) was passed through the resin to convert the dimethylammonium chloride to the nitrate.  The 
aqueous effluent was evaporated using a rotary evaporator (Büchi) to recover the dimethylammonium 
nitrate.  This was then repeated using new anion exchange resin and aqueous sodium nitrite.  
Dimethylammonium nitrite could not be formed using this method.  Aqueous sodium nitrite was used with 
the dimethylammonium nitrate as a substitute for dimethylammonium nitrite. 
 
PREPARATION OF UFORP RESIDUE 
 
UFORP (1.0354 g) in a quartz bowl was placed inside a vacuum system at ambient temperature, as 
shown in Figure 2.  The UFORP was subjected to 10-3 Torr for 5 days.  The UFORP residue was 
removed and weighed 9.85 x 10-2 g. 
 
 
Figure 2.  UFORP Evaporation Rate Vacuum System 
 
 
EVAPORATION RATE TESTING 
 
The vacuum system was evacuated to ~10-3 Torr as indicated on the thermocouple gauge, then back-
filled with nitrogen gas.  The copper cold plate inside the vacuum chamber was cooled to -40 °C by 
running a chilled methanol and water mixture through a tube welded to the copper plate.  Five glass 
slides were numbered 1 to 5 with an engraving tool and tared.  A 250 µL syringe was filled with 200 µL 
UFORP, capped and weighed.  The UFORP in the syringe was placed onto the first glass slide, which 
was immediately placed on the cooled copper plate.  The syringe was capped and weighed again.  The 
process was repeated for the remaining four glass slides.  Ten minutes after the last slide was placed on 
the copper plate to allow it to cool to -40 °C, the vacuum system was started.  The slides were removed 
from the vacuum chamber at selected time intervals.  Each slide was placed into a desiccator and 
allowed to warm to room temperature before it was reweighed.  The slides were then rinsed with two 1 
mL aliquots of dichloromethane and collected into separate sample vials.  The dichloromethane rinses 
were analyzed by gas chromatography-mass spectroscopy (GC-MS, Agilent model 6890N GC equipped 
with an Agilent model 5973 Network mass selective detector). 
 
The process was repeated for the synthetic UFORP.  The copper plate was then set to 0 °C, and the 
process was repeated for UFORP and synthetic UFORP.   
 
SOLID PHASE MICROEXTRACTION 
 
The headspace above the UFORP residue was sampled at various time intervals using a solid phase 
microextraction (SPME) injector equipped with a poly(dimethylsilane) on divinylbenzene fiber (Supelco®1).  
The SPME needle was inserted through a septum located in the lid of the sample container and the fiber 
                                                     
1 Supelco® is a registered trademark of the Sigma-Aldrich Co., Highland, Illinois. 
was extended into the headspace gas for 1 minute.  Then the fiber was removed and immediately 
analyzed by GC-MS. 
 
RESULTS AND DISCUSSION 
 
EVAPORATION RATE STUDIES 
 
UFORP.  The weight of the UFORP after being subjected to 10-3 Torr at -40 °C and 0 °C was used to 
calculate the weight percent remaining.  These residues, expressed as percent remaining, are shown in 
Figure 3.  The concentration of NDMA remaining was calculated from 2 mL dichloromethane rinse 
solutions of the residues.  The results are shown in Figures 4 and 5. 
 
Figure 3 shows that the weight of the UFORP decreased with time.  Over 85% of the weight was 
removed by subjecting the UFORP to 10-3 Torr for 7 hours at -40 °C and 0 °C.  Figures 4 and 5 show that 
the NDMA concentration decreased with time at -40 °C and 0 °C, but still remained at low levels.  
 
SYNTHETIC UFORP.  The synthetic UFORP, prepared as described, contained 36% UDMH, 36% 
NDMA, 8% dimethylammonium nitrate, 6% sodium nitrite (equimolar to the nitrate), and 14% water.  The 
quantity of UFORP residue remaining after selected time intervals at -40 °C and 0 °C are shown in Figure 
6.  
 
Figure 6 shows the UFORP weight decreased significantly with time.  Over 90% of the weight was 
removed by subjecting the UFORP to 10-3 Torr for 22 hours at -40 °C and for 30 minutes at 0 °C.  The 
NDMA concentration immediately decreased from approximately 360,000 ppm to 140 ppm before the first 
measurement at -40 °C and to 10 ppm at 0 °C. 
 
 
0
10
20
30
40
50
60
0.00 5.00 10.00 15.00 20.00 25.00 30.00 35.00
Time (hours)
Pe
rc
en
t R
em
ai
ni
ng
 -40C 0C  
Figure 3.  Weight percent remaining from evaporation of UFORP at -40 °C and 0 °C, 10-3 Torr 
 
0500
1000
1500
2000
2500
3000
3500
4000
0.00 5.00 10.00 15.00 20.00 25.00 30.00 35.00
Time (hours)
C
on
ce
nt
ra
tio
n 
(p
pm
)
-40C UFORP  
Figure 4.  NDMA concentration from evaporation of UFORP at -40 °C, 10-3 Torr.  The starting NDMA 
concentration was approximately 8,000 ppm. 
 
0
2
4
6
8
10
12
14
16
0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00
Time (hours)
C
on
ce
nt
ra
tio
n 
(p
pm
)
 0C  
Figure 5.  NDMA concentration from evaporation of UFORP at 0 °C, 10-3 Torr.  The starting NDMA 
concentration was approximately 8,000 ppm.  
 
 
 
0.0
5.0
10.0
15.0
20.0
25.0
30.0
0.00 5.00 10.00 15.00 20.00 25.00
Time (hours)
Pe
rc
en
t R
em
ai
ni
ng
 -40C 0C  
Figure 6.  Weight percent remaining from evaporation of synthetic UFORP  
at -40 °C and 0 °C, 10-3 Torr 
 
NDMA FORMATION TESTING 
 
Three separate mixtures were studied in air under ambient temperature and pressure.  The first 
mixture contained dimethylammonium nitrate (2.3 g), sodium nitrite (1.6 g) and 1 mL of purified water, 
which were all added simultaneously.  An initial analysis of the headspace by SPME/GC-MS was 
performed immediately after mixing the components and 3400 ppm NDMA was found.  After 27 hours, 
9,000 ppm NDMA was found. 
 
To see whether NDMA formation was dependent on each component, a second mixture was made 
which at first contained only dimethylammonium nitrate (1.5 g).  The dimethylammonium nitrate was 
analyzed at various time intervals and NDMA concentration stayed at approximately 700 ppm over a 5-
hour period.  After the addition of 1 mL of water, NDMA concentrations dropped to approximately 100 
ppm.  The mixture was monitored for 2 hours after the addition of water, then sodium nitrite (1.0 g) was 
added.  The mixture formed NDMA rapidly.  Figure 7 shows the rate of formation of NDMA from this 
mixture after sodium nitrite was added. 
 
To determine the effect of the synthesized dimethylammonium nitrate, a third mixture containing only 
dimethylammonium chloride (2.0 g), sodium nitrate (2.0 g), and 1 mL of water, was analyzed over a 22-
hour period and no NDMA was detected (detection limit = 25 ppm).  After the addition of sodium nitrite 
(1.6 g), NDMA formed rapidly.  Figure 8 shows the rate of formation of NDMA from this mixture after the 
addition of sodium nitrite. 
 
02000
4000
6000
8000
10000
12000
14000
16000
18000
0 5 10 15 20 25 30
Time (days)
N
D
M
A
 C
on
ce
nt
ra
tio
n 
(p
pm
)
 
Figure 7.  Formation of NDMA from mixture of  
dimethylammonium nitrate, water, and sodium nitrite 
          
 
 
0
2000
4000
6000
8000
10000
12000
14000
16000
0 5 10 15 20 25 30
Time (d)
C
on
ce
nt
ra
tio
n 
(p
pm
)
 
Figure 8.  Formation of NDMA from mixture of dimethylammonium chloride, 
sodium nitrate, water, and sodium nitrite 
 
UFORP Residue.  When the UFORP residue was removed from the vacuum system, it appeared as a 
shiny, highly viscous liquid as shown in Figures 9 and 10.  Most of the UFORP residue (60.9 mg) was 
placed into a tared 40 mL ICHEM vial using a spatula.  The remaining UFORP residue was rinsed from 
the quartz bowl into a 40 mL ICHEM vial with 1 mL of water. 
 
 
 
Figure 9.  UFORP residue inside vacuum chamber at 10-3 Torr after 26 hours 
 
 
 
Figure 10.  UFORP residue (0.06 g) after 26 hours exposure to 10-3 Torr 
 
The UFORP residue and the UFORP residue rinsed with 1 mL of water were analyzed by SPME/GC-
MS for 2 days and no NDMA was found.  The UFORP residue rinsed with water was spiked to 100 ppm 
NDMA and 100 ppm was recovered, ruling out a detection problem due to the matrix of the UFORP.  The 
UFORP residue was monitored for a total of 4 days and no NDMA was detected in the headspace.   
 
To determine why the UFORP residue was not forming NDMA, some UFORP residue (9.9 mg) was 
added to 1 mL of water.  The sample was analyzed for nitrate and nitrite by ion chromatography (IC) 
using a Dionex®1 Model DX-600 ion chromatograph equipped with a conductivity detector and a Dionex 
AS14 anion exchange column.  Ammonium, methylammonium, and dimethylammonium were determined 
using the same IC but with a Dionex CS16 cation exchange column.  An analysis of the ions present in 
the UFORP water solution by IC showed there was minimal nitrite in the UFORP residue.  Table 1 shows 
the IC results. 
 
Sodium nitrite (3.3 mg) was added to the UFORP residue (22.1 mg) remaining in the 40 mL ICHEM 
vial to see if NDMA would form due to nitrite.  The headspace above the mixture was analyzed by 
SPME/GC-MS at various time intervals.  NDMA formed rapidly after the addition of sodium nitrite.  The 
results are shown in Figure 11. 
 
Table 1.  IC results for UFORP residue in water 
Component Amount (µg) Weight Percent 
Nitrite 7.9 0.08% 
Nitrate 3600 36% 
Ammonium 5.3 0.05% 
Methylammonium 110 1.1 % 
Dimethylammonium 780 7.9% 
 
 
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
0 0.5 1 1.5 2 2.5 3 3
Time (days)
C
on
ce
nt
ra
tio
n 
(p
pm
)
.5
                                                     
 
Figure 11.  NDMA Formation from NaNO2 and UFORP residue 
1 Dionex® is a registered trademark of the Dionex Corporation, Sunnyvale, California. 
CONCLUSIONS 
 
The analysis of UFORP and synthetic UFORP subjected to a simulated space vacuum showed that 
NDMA concentration decreased in a space environment even at –40 °C.  However, NDMA is not 
completely removed from UFORP after 29 hours in a space-like environment  
(-40 °C, 10-3 Torr).  
 
NDMA was readily formed when a mixture of dimethylammonium nitrate, water, and sodium nitrite are 
exposed to air in a laboratory environment.  The same is true for the mixture of water, laboratory reagent-
grade dimethylammonium chloride, sodium nitrate, and sodium nitrite.  NDMA was not formed from 
UFORP residue alone, likely due to the low nitrite concentration.  When sodium nitrite was added to the 
UFORP residue, NDMA began to form immediately and rapidly. 
 
REFERENCES 
 
1. Dee, L.A. and V.D. Davidson.  Laboratory Preparation and Characterization of UDMH/NO2 Reaction 
Products, WSTF-IR-0168-001-02, NASA Johnson Space Center White Sands Test Facility, Las 
Cruces, NM, April 29, 2002. 
 
2. Liteplo, R.G. and M.E. Meek.  N-Nitrosodimethylamine, 
http://www.inchem.org/documents/cicads/cicads/cicad38.htm. 
 


Evaporation Rate Study and NDMA Formation from UDMH/NO2 Reaction Products

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server