VOLATILE NITROSAMINE MIXTURE I
N-NITROSODIMETHYLAMINE (NDMA)
N-NITROSODIETHYLAMINE (NDEA)
N-NITROSODI-n-PROPYLAMINE (NDPA)
N-NITROSODI-n-BUTYLAMINE (NDBA)
N-NITROSOPIPERIDINE (NPIP)
N-NITROSOPYRROLIDINE (NPYR)
N-NITROSOMORPHOLINE (NMOR)
Method no.: | 27 |
|
OSHA PEL: |
The OSHA standard applies to all solid or liquid mixtures containing more than 1% NDMA by weight or volume. |
|
Procedure: |
Samples are collected using ThermoSorb/N air samplers. The
samples are desorbed with a 75/25 (v/v) dichloromethane/methanol
solution. Analysis is performed by gas chromatography with
Thermal Energy Analyzer detection. |
|
Recommended air volume and sampling rate: |
75 L at 1 L/min (0.2 to 2 L/min is permissible). |
|
Special requirements: |
It is recommended that samples be stored in a freezer. |
|
Status of method: |
A sampling and analytical method that has been subjected to the
established procedures of the Organic Methods Evaluation Branch. |
|
Date: February 1981 |
Chemist: Warren Hendricks |
Organic Methods Evaluation Branch
OSHA Analytical Laboratory
Salt Lake City, Utah
Volatile Nitrosamine Mixture I
|
analyte | | NDMA | NDEA | NDPA | DNBA | NPIP | NPYR | NMOR |
|
target concentration reliable quantitation limit
|
ppb µg/m3 ppb µg/m3 |
0.89 2.7 0.043 0.13
|
0.65 2.7 0.031 0.13
|
0.51 2.7 0.024 0.13
|
0.37 2.4 0.019 0.12
|
0.51 2.4 0.026 0.12
|
0.66 2.7 0.032 0.13
|
0.84 4.0 0.042 0.20
|
standard error of estimate at target concentration, (Section 4.7.) |
| % | 5.81 | 6.24 | 6.22 | 6.26 | 5.74 | 5.86 | 6.28 |
All values based on the recommended air volume. |
1. General
1.1. Background
1.1.1. History
The purpose of this work was to develop a general sampling and analytical
procedure for volatile N-nitrosamines. This method is intended to supersede
previous OSHA methods which were each evaluated for only one N-nitrosamine.
This method is superior to previous methods because it permits the industrial
hygienist to monitor seven different N-nitrosamines with a single sample.
Volatile N-nitrosamines have been collected using successive cold traps
(-79 to -95°C) in series (Ref. 5.1.),
ambient temperature KOH bubblers (Ref. 5.2.), pH 4.5 ascorbic acid
bubblers (Ref. 5.3.) and solid sorbents which include Tenax GC
(Ref. 5.4.), activated charcoal-water suspension
(Ref. 5.5.), vitamin E and C treated Florisil adsorbent tubes
(Refs. 5.6. and 5.7.), XAD-4 resin
(Ref. 5.8.) and ThermoSorb/N commercial nitrosamine air samplers
(Ref. 5.9.). Activated alumina, silica gel and Florisil adsorbents
have been tested, but not widely used to sample air for nitrosamines (Ref. 5.9.).
Many of these air sampling techniques have serious deficiencies. The cold traps
are difficult to maintain and are reported to enable the artifactual formation of
NDMA from precursor amines and nitrogen oxides (Ref. 5.10.). The
ambient temperature KOH and ascorbic acid bubblers are free of artifact formation but
analyte retention efficiency decreases with increasing sampling time and temperature
(Ref. 5.9.). Tenax GC has a relatively low breakthrough volume for
NDMA (Ref. 5.9.). Solid adsorbents, in general, may concentrate
precursor amines and nitrosating agents resulting in artifactual in situ formation of the
analyte (Ref. 5.9.). The vitamin E and C treated Florisil adsorbent
tubes were shown to be artifact resistant, but no one device was adequate for use as a
general-purpose nitrosamine air sampler (Ref. 5.7.).
Because of the many problems associated with alternative air sampling techniques,
it was decided to evaluate the ThermoSorb/N air sampling system. The device is
a commercially available opaque plastic cartridge containing a solid adsorbent.
The manufacturer states that the device is designed to prevent the artifactual
formation of the analytes because of a proprietary amine trap and nitrosation inhibitor.
Almost all analytical methods for N-nitrosamines utilize some sort of
chromatographic separation procedure prior to detection of the analyte. Some
samples, which usually have a simple matrix, have been determined directly using
polarographic and spectrophotometric methods. These techniques are subject to
interferences and have limited application for low level analysis of complex samples
(Ref. 5.11.).
Thin layer chromatographic (TLC) techniques have been used to determine
N-nitrosamines. The analytes have been chromatographed before and after
derivatization. The derivatives include nitramines, fluorescent dansyl products,
fluorescent hydrazones and hydrazines. The underivatized analyte has been
visualized using sprays that form a colored complex with the parent secondary
amine obtained by exposing the chromatographed N-nitrosamines to ultraviolet
(UV) light. The main advantages of TLC methods are that they are simple,
inexpensive and some have very low detection limits. The main disadvantages are
that they are only semiquantitative and do not have sufficient resolution
(Ref. 5.11.).
High performance liquid chromatographic (HPLC) techniques have been used to
determine complex mixtures of N-nitrosamines. The analytes have been
chromatographed and detected as N-nitrosamines and as 2,4-dinitrophenyl
derivatives of the parent secondary amine. The UV detector is usually employed
in these methods. Advantages of HPLC procedures include the capability to
chromatograph non-volatile and thermally labile analytes. The main disadvantage
has been the lack, until recently, of selective detectors (Ref. 5.11.).
The most widely used technique to separate complex mixtures of volatile
N-nitrosamines is gas chromatography (GC). Volatile derivatives of non-volatile
N-nitrosamines have been prepared for GC analysis also.
Volatile N-nitrosamines chromatograph quite well on stainless
steel columns and there is no apparent advantage to using glass GC columns. The GC column
packing most used is 10% Carbowax 20M with 2% KOH on 80/100 mesh acid washed Chromosorb W.
Other stationary phases that have been used are Reoplex 400, FFAP, Carbowax 1540, BDS and
Versamid. Capillary and SCOT columns have been used and very good peak resolution has been
obtained (Ref. 5.11.).
Most of the commonly available GC detectors have been used to determine
N-nitrosamines. These detectors include the flame-ionization
detector, nitrogen selective alkali flame-ionization detector, Coulson Electrolytic Conductivity
Detector and Hall Electrolytic Conductivity Detector. Derivatives that are sensitive to
electron capture detectors have been prepared from N-nitrosamines.
The main disadvantage to these detectors is that they are not selective for
N-nitrosamines. Modified Hall and Coulson Electrolytic Conductivity detectors
have been used to increase selectivity to N-nitrosamines.
The Hall detector is very similar in principle to the Coulson detector. In the
normal operation of these detectors, the GC column effluent is mixed with
hydrogen gas and passed through a heated quartz reaction tube containing a nickel
catalyst. The nitrogen containing analyte is reduced to ammonia which is
measured by a change in the conductivity of water in the detector cell. Acidic
interferences are removed with a scrubber. The catalyst is removed to modify the
detectors and the modified detectors respond only to N-nitrosamines and amines
(Ref. 5.11.).
Since mass spectrometry provides an unequivocal means to confirm chemical structure,
it has been used as a GC detector in the determination of complex mixtures containing
N-nitrosamines (Ref. 5.4.).
The Thermal Energy Analyzer (TEA) is a highly selective detector for N-nitroso
compounds that has been successfully interfaced to gas and liquid
chromatographs. In the GC mode of operation, the chromatographed N-nitroso
compound exits the GC and enters the TEA pyrolyzer through a heated transfer
line. The chemical bond between the two nitrogen atoms (N-NO) is thermally
broken, resulting in an organic fragment and a nitrosyl radical (¯NO). Organic
compounds, solvents and fragmentation products are collected in a cold trap. The
nitrosyl radical is a stable gas which passes through the cold trap to react with
ozone under vacuum to form electronically excited nitrogen dioxide. The excited
nitrogen dioxide quickly decays to its ground state and emits light, at a
characteristic wavelength, which is measured by a photomultiplier tube. When
the TEA is used as an HPLC detector, the sequence of events is similar to those
of the GC mode. The chromatographed analyte exits the HPLC column and enters the TEA
pyrolyzer. A higher temperature pyrolyzer is used because the HPLC mobile phase is
flashed at the same time the N-nitroso bond is thermally broken. The vaporized
HPLC mobile phase, organic compounds and fragmentation products are condensed in a cold trap. The nitrosyl radical is swept through the cold trap with an
inert gas, usually helium or argon, and is detected as before (Ref. 5.48.).
This method recommends separation by GC and detection with the TEA. An HPLC method is also presented for use as a confirmatory procedure.
1.1.2. Toxic effects (This section is for information only and should not be taken as the basis of OSHA policy).
Detailed toxicology information regarding chronic exposure to the individual analytes is
presented in Section 4.8. Much of the toxicology data regarding the
analytes have been obtained using rats as the test species and that work is
presented in this method. Some of the analytes have been investigated using other
species and similar toxic effects have been observed.
The effects of acute exposure to each of the analytes were similar. The
administration of a lethal dose to rats led to a gradually advancing weakened,
emaciated condition frequently with the appearance of jaundice. Death usually
occurred within seven days. The autopsy revealed severe centrilobular liver
damage with hemorrhaging into the lungs in most cases. The response to a lethal
dose was the same for male and female rats (Ref. 5.12).
Chronic exposure to the analytes has led to cancer in a number of different animal species
(Ref. 5.15). The carcinogenic potential of the analytes varies over
a wide range and depends on the compound, route of administration, level of dose,
frequency of dose and length of the exposure.
N-nitrosodialkylamines do not appear to be directly active carcinogens. If the
compounds were directly active, local sarcomas should be observed at the site of
subcutaneous injection because of the high concentration of the agent and
sensitivity of the subcutaneous tissue. If, however, local sarcomas do not develop
and tumors in distant organs are observed, the agent is an intermediate from
which the ultimate carcinogen is produced by metabolic processes. Subcutaneous
injection of N-nitrosodialkylamines did not result in local sarcomas and the
carcinogenic effects were evident in specific organs (lungs, liver, bladder, etc.).
The N-nitrosodialkylamines are, therefore, considered not to be the ultimate
carcinogens (Ref. 5.12.).
The carcinogenic effects of dialkylnitrosamines on the molecular level, is thought
to be the result of an alkylation of nucleic acids. The metabolic activation of a
N-nitrosodialkylamine involves the enzymatic hydroxylation of the carbon atom
immediately adjacent (in the alpha position) to the N-nitroso group. Several
intermediate species are formed, one of which is diazoalkane. The ultimate
carcinogen is believed to be a carbonium ion. A schematic of the proposed
biological activation process is presented in Figure 1.1.2.
The theory is supported by the fact that exposure of rats to
ethyl-tert-butylnitrosamine, which cannot form a diazoalkane, was not
carcinogenic, even in high doses. Exposure to ethyl-n-butylnitrosamine,
however, did lead to cancer in rats (Ref. 5.12.).
The mechanism by which the cyclic N-nitrosamines (NPIP, NPYR, NMOR, etc.) exert
their carcinogenic action is not as clear as that for the dialkylnitrosamines.
It is unknown if the rings contained in these cyclic compounds can be biologically
opened to form the diazoalkane intermediate. The formation of diazoalkane or
other alkylating species is unlikely if the rings cannot be opened
(Ref. 5.17). It has been shown that exposure to NPIP, NPYR
and NMOR will result in alkylation of RNA in rat liver. These results support the theory
that alkylation of nucleic acids is important to the carcinogenic effects of
N-nitroso compounds (Ref. 5.17).
In addition to carcinogenic activity, the analytes all have mutagenic effects. In
early studies, N-nitrosamines were found to be mutagenic only in tests with
Drosophilia melanogaster (Fruit Fly) and no activity was observed in tests using
bacteria, yeasts or fungi. The reason for lack of activity in the microorganisms
is that Drosophilia can biologically activate nitrosamines while the others cannot.
This conclusion is supported by the fact that NDMA is mutagenic to bacteria
when incubated with rat liver microsomes. Therefore, in order to exert mutagenic
effects, the analytes must be biologically activated (Ref. 5.18).
All seven of the N-nitrosamines covered in this method exert a powerful
carcinogenic action on experimental animals. While there is no direct evidence
that exposure to the analytes can cause cancer in humans, the wide range of
species that is susceptible to their carcinogenic action suggests that man is
probably not resistant (Ref. 5.19).
The International Agency for Research on Cancer, (IARC) recommends that all
seven of the analytes should be treated as if they were carcinogenic to humans
(Ref. 5.14).
1.1.3. Exposure
NDMA has been employed as an industrial solvent and in the synthesis of the
rocket fuel 1,1-dimethylhydrazine. Patents and proposed uses include, as an
antioxidant, a softener for copolymers, an additive for lubricants, in condensers
to increase the dielectric constant and a nematocide (Ref. 5.20). NDEA has been
suggested for use as a solvent, a softener for copolymers, a lubricant additive, in
electrical condensers and chemical synthesis (Ref. 5.20). NDBA has been tested
as a fungicide and used in chemical synthesis (Ref. 5.21).
Patents exist for the use of NMOR as a solvent for polyacrylonitrile and as a
intermediate for the synthesis of N-aminomorpholine. NMOR has been found to
be an effective agent to combat microbial infections (Ref. 5.14).
The use of NDMA was discontinued in 1976 and, at present, there is no evidence that any
of the analytes are intentionally produced for other than research purposes
(Ref. 5.14.).
Some of the analytes have been determined to be present in beers (Ref. 5.22),
whiskeys (Ref. 5.23), tobacco (Ref. 5.24), tobacco smoke
(Ref. 5.24), herbicides (Ref. 5.25), deionized
water (Ref. 5.26), free amines (Ref. 5.27.),
corrosion inhibitors (Ref. 5.28.), diesel engine crankcase emissions
(Ref. 5.29.) and new car interiors (Ref. 5.30.).
Industries in which some of the analytes have been detected include iron foundries
(Ref. 5.30.), leather tanneries (Ref. 5.31.),
rubber producing factories (Ref. 5.32.) and rubber products
manufacturing plants (Ref. 5.32.).
N-nitrosamines are extensively used in cancer research facilities. Human exposure
can occur when the unchanged agents are excreted by the laboratory animals.
Non-occupational sources of exposure to the analytes are the endogenous
formation of the agents in the human gastrointestinal tract. Precursor amines have
been shown to react with nitrite to form the corresponding N-nitrosamines
under conditions found in the mammalian stomach (Ref. 5.38.).
NMOR has been produced in vivo by mice gavaged with morpholine and later exposed to nitrogen
dioxide in inhalation chambers (Ref. 5.39.). The source of volatile
N-nitrosamines found in normal human feces, urine and saliva has been suggested
to be in vivo nitrosation of ingested secondary and tertiary amines
(Refs. 5.40. 5.42.).
The size of the work population that is exposed is unknown. Since amines and
suitable nitrosating species are ubiquitous the number of potential exposures seems
large (Ref. 5.43.).
Because the analytes are such powerful animal carcinogens, they are probably not
used to any great degree by U.S. industry today. Most occupational exposure to
the analytes is probably the result of the unintentional formation of the agent from
precursor amines and suitable nitrosating species. The amino group can be
primary, secondary or tertiary (Ref. 5.36.). The amine can be free
or a portion of a more complex molecule such as a drug or a herbicide. Amines can be
nitrosated in air (Ref. 5.34.) or in solution under acidic, neutral or alkaline
conditions (Ref. 5.36.). The nitrosation reaction is catalyzed by
thiocyanate, halide ions, metal ions, formaldehyde and ozone
(Refs. 5.35. and 5.36.). Suitable
nitrosating species include nitrogen oxides (NO, NO2,
N2O3,
N2O4), nitrite and nitrous acid
(Ref. 5.36.). Nitrosation can occur as a result of transnitrosation.
This is a chemical reaction in which a N-nitrosamines transfers its
nitroso group to another amine (Ref. 5.37.).
1.1.4. Physical properties
The following data were taken from Refs. 5.13. and 5.44.
|
analyte | | NDMA | NDEA | NDPA | NPIP |
|
CAS no.:
molecular weight:
boiling point, °C/mm Hg:
density, g/mL:
refractive index:
physical appearance: |
62-75-9 74.08 154/760 1.0059 1.4358 yellow liquid |
55-18-5 102.14 176.9/760 0.9422 1.4386 yellow liquid |
621-24-7 130.19 206/760 0.9163 1.4437 yellow liquid |
100-75-4 114.15 217/721 1.0631 1.4933 yellow liquid |
solubility UV absorption |
water: alcohol: ether: l max, nm: log e: l max, nm: log e: l max, nm: log e: |
v. sol. v. sol. v. sol. 231 3.85 346 2.00 |
v. sol. v. sol. v. sol. 231 3.7 350 1.95 |
sol. miscible miscible 233 3.85 350 1.95 |
sol. 354 1.91 366 2.04 377 2.00 |
|
The following data were taken from Refs. 5.13. and 5.14.
|
analyte | | NDBA | NPYR | NMOR |
|
CAS no.:
molecular weight:
boiling point, °C/mm Hg:
density, g/mL (20//4):
refractive index:
melting point, °C:
physical appearance: |
924-16-3 158.2 116/14 0.9009 1.4475 yellow oil |
930-55-2 100.2 214/760 yellow liquid |
59-89-2 116.1 224/747 29 yellow solid |
solubility UV absorption |
water: org. solv.: lipids: l max, nm: log e: l max, nm: log e: |
0.12% sol. sol. sol. 233 2.65 347 0.75 |
miscible sol. sol. 230 2.91 333 1.03 |
miscible sol. 237 2.84 346 0.86 |
|
Synonyms (Ref. 5.13.)
N-nitrosodimethylamine
dimethylnitrosamin (German); dimethylnitrosamine; N,N-dimethylnitrosamine;
N-methyl-N-nitrosomethanamine; dimethylnitrosoamine; DMN; DMNA; NDMA.
N-nitrosodiethylamine
diaethylnitrosamin (German); diethylnitrosamine; diethylnitrosoamine; N,N-diethylnitrosamine;
ethylamine, N-nitrosodi-; N-ethyl-N-nitroso ethanamine; nitrosodiethylamine; DANA; DEN;
DENA; NDEA.
N-nitrosodipropylamine
di-n-propylnitrosamine; N-nitrosodi-n-propylamine; N-nitroso-N-propyl-1-propanamine;
propylamine, N-nitroso-N-di-; propanamine, N-nitroso-Npropyl; DPN; DPNA; NDPA.
N-nitrosodibutylamine
butylamine, N-nitrosodi-; N-butyl-N-nitroso-1-butamine; dibutylamine, N-nitroso-;
di-n-butylnitrosamin (German); dibutylnitrosamine; di-n butylnitrosamine;
N,N-di-n-butylnitrosamine; N-nitroso-di-n-butyl amine; DBN; DBNA; NDBA.
N-nitrosoiperidine
nitrosopiperidin (German); N-nitroso-piperidin (German); 1-nitrospi
peridine; NO-Pip; NPIP.
N-nitrosopyrrolidine
N-nitrosopyrrolidin (German); pyrrolidine, 1-nitroso-; NO-Pyr; NPYR.
N-nitrosomorpholine
morpholine, 4-nitroso-; N-nitrosomorpholin (German); 4-nitrosomorpho line; NMOR.
molecular formula (Ref. 5.14)
NDMA - (CH3)2NNO |
NPIP - PIP-NO (C5H10N2O) |
NDEA - (C2H5)2NNO |
NPYR - PYR-NO (C4H8N2O) |
NDPA - (C3H7)2NNO |
NMOR - MOR-NO (C4H8N2O2) |
NDBA - (C4H9)2NNO |
See Figure 1.1.4. for the molecular structures of the analytes.
1.2. Limit defining parameters
The air samplers were vapor spiked with the analytes by the liquid injection of a certified
mixture on Polar Partition tubes. The spiked tubes were placed in front of ThermoSorb/N
air samplers and then 50 L (1 L/min) of air, at about 80% relative humidity and 22°C,
were drawn through the sampling train. The N-nitrosamines were vaporized from the
Polar Partition tubes and collected on the ThermoSorb/N tubes. The vaporization process
was shown to be complete after about 25 L had passed through the Polar Partition tubes.
The analytes were vapor spiked on the air samplers as components of a commercially
prepared, certified mixture. The mixture was prepared and certified by Thermo Electron
Corporation and their results are presented below.
|
NDMA | NDEA | NDPA | NDBA | NPIP | NPYR | NMOR |
|
10 | 10 | 10 | 9 | 9 | 10 | 15 |
|
1.2.1. Detection limits of the analytical procedure
The detection limit of the analytical procedure is the amount of analyte per injection
which will result in a peak whose height is about 5 times the amplitude of the base line noise.
The detection limits are presented below as mass per injection. (Section 4.1.)
The Detection Limits of the Analytical Procedure, pg
|
NDMA | NDEA | NDPA | NDBA | NPIP | NPYR | NMOR |
|
50 | 50 | 50 | 45 | 45 | 50 | 75 |
|
1.2.2. Detection limits of the overall procedure
The detection limit of the overall procedure is the amount of analyte spiked on the
sampling device which allows recovery of an amount of analyte equivalent to the
detection limit of the analytical procedure. (Section 4.2.)
The Detection Limits of the Overall Procedure
|
analyte | NDMA | NDEA | NDPA | NDBA | NPIP | NPYR | NMOR |
|
ng/sample ppb µg/m3 |
10 0.043 0.13 |
10 0.031 0.13 |
10 0.024 0.13 |
9 0.019 0.12 |
9 0.026 0.12 |
10 0.032 0.13 |
15 0.042 0.20 |
All values based on the recommended air volume. |
1.2.3. Reliable quantitation limits
The reliable quantitation limit is the smallest amount of analyte which can be
quantitated within the requirements of 75% recovery and 95% confidence limits of ±25%.
The reliable quantitation limits were the same as the detection limits of the overall
procedure since the desorption efficiencies were above 75% and the 95%
confidence intervals were less than ±25%. (Section 4.2.)
The Reliable Quantitation Limits
|
analyte | NDMA | NDEA | NDPA | NDBA | NPIP | NPYR | NMOR |
|
ng/sample ppb µg/m3 |
10 0.043 0.13 |
10 0.031 0.13 |
10 0.024 0.13 |
9 0.019 0.12 |
9 0.026 0.12 |
10 0.032 0.13 |
15 0.042 0.20 |
All values based on the recommended air volume. |
The reliable quantitation limit and detection limits reported in the method are based upon
optimization of the instrument for the smallest possible amount of analyte. When the
target concentration of an analyte is exceptionally higher than these limits, they may not
be attainable at the routine operating parameters.
1.2.4. Sensitivity
The sensitivity of the analytical procedures is determined by the slope of the
calibration curves over a concentration range from 0.5 to 2 times the target
concentrations. The sensitivity will vary somewhat with the particular instrument
used in the analysis. (Section 4.4)
The Sensitivity of the Analytical Procedures
|
analyte | NDMA | NDEA | NDPA | NDBA | NPIP | NPYR | NMOR |
|
area units per µg/mL |
239864 | 208144 | 163134 | 129648 | 179720 | 201661 | 176596 |
|
1.2.5. Recovery
The recovery of the analytes from the collection medium must be 75% or greater.
The average recoveries from spiked samples over the range of 0.5 to 2 times the
target concentrations are presented below. (Section 4.6.)
Average Desorption Efficiencies, %
|
NDMA | NDEA | NDPA | NDBA | NPIP | NPYR | NMOR |
|
97.4 | 99.7 | 98.9 | 97.7 | 96.0 | 97.6 | 98.1 |
|
1.2.6. Precision (analytical method only)
The pooled coefficients of variation obtained from replicate determinations of
analytical standards at 0.5, 1 and 2 times the target concentrations are presented below.
(Section 4.3.)
The Pooled Coefficients of Variation
|
NDMA | NDEA | NDPA | NDBA | NPIP | NPYR | NMOR |
|
0.037 | 0.044 | 0.048 | 0.047 | 0.051 | 0.040 | 0.032 |
|
1.3. Advantages
1.3.1. The sampling and analytical procedures permit the simultaneous determination of a mixture of analytes.
1.3.2. The sampling and analytical procedures are precise, reliable, safe and convenient.
1.3.3. The sampling procedure is artifact free. The capacity of the sampling device to prevent artifacts is probably not unlimited.
1.3.4. The air sampling device is commercially available and is constructed of opaque plastic to prevent photo-degradation of the collected N-nitrosamines.
1.3.5. The samples are stable when stored at ambient temperatures for at least 17 days.
1.4. Disadvantages
1.4.1. Smaller laboratories may not be able to support the cost of the recommended sampling and analytical instrumentation.
1.4.2. The ability of the sampling device to collect and retain the analytes is limited.
2. Sampling Procedure
2.1. Apparatus
2.1.1. An air sampling pump, the flow of which can be determined to within ±5% at the recommended air flow rate with the air sampler in line.
2.1.2. ThermoSorb/N air sampling cartridges available from Thermo Electron Corporation, Waltham, Mass.
2.1.3. Equipment to measure the air flow rate through the sampling device.
2.2. Reagents
None required
2.3. Technique
2.3.1. Prior to sampling, remove the ThermoSorb/N air sampling device from the foil
container. Save the container so it can be used for sample shipment.
2.3.2. Prior to sampling, remove the red end caps from the inlet and outlet ports. Store
the caps on the air sampler in the places that are provided for this use.
2.3.3. Label the air sampler and attach the device to the air sampling pump with flexible
tubing. Adjust the pump to obtain the proper air flow rate. The recommended rate is
1 L/min, but flow rates of from 0.2 to 2 L/min may be used. If air volumes larger than the
recommended 75 L are to be sampled or if large amounts of N-nitrosamines are
suspected, two air samplers may be connected in series. Always calibrate the pump with the
sampling device in line.
2.3.4. Attach the sampling device in the breathing zone of the employee to be monitored.
The molded clip is convenient for this purpose.
2.3.5. After sampling for the appropriate time, remove the device and replace the red
end caps on the inlet and outlet ports of the sampler.
2.3.6. Wrap each sample end to end with official OSHA seals. Place the sealed air
sampler inside the foil container from Section 2.3.1.
2.3.7. With each set of samples, submit at least one blank sample. The blank should be
subjected to the same handling as the sample except that no air is drawn through it.
2.3.8. Place the samples in a freezer if they are to be stored before shipping to the laboratory.
2.3.9. List possible interferences on the sample data sheet.
2.4. Breakthrough
Breakthrough studies were conducted by connecting two air samplers in series. The first
air sampler was vapor spiked with twice the target concentration of the mixture and then
air at 80% relative humidity and 22°C was drawn through the sampling train. Both air
samplers were analyzed after the appropriate air volume had been sampled. Percent
breakthrough was defined as the amount of a component found on the second
ThermoSorb/N tube divided by the amount of that component vapor spiked on the first
tube, multiplied by 100.
NDMA was the only component of the mixture that was lost from the first sampling device.
Five-percent breakthrough occurred after about 100 L of air had been sampled.
The experiment was repeated with NDMA as the only analyte vapor spiked and similar results
were obtained. These results indicate the capacity of the tube was not exceeded by the mixture
(3 µg of N-nitrosamines). The manufacturer reports that 1500 µg of
N-nitrosamines may exceed the capacity of a single tube (Ref. 5.45.).
It was found that as much as 280 L of air may be sampled for NDMA with no loss of the
agent if two ThermoSorb/N tubes were connected in series. When 400 L of air were
sampled at 2 L/min, about 16% of the NDMA vapor spiked on the first tube was lost from
the sampling train. All of the recovered NDMA was found on the second tube. None of
the other components moved from the first tube.
When the relative humidity was decreased from 80%, the 5% breakthrough air volume
for NDMA was found to increase. At 63% relative humidity, over 200 L of air was
sampled with no NDMA breakthrough. The complete results of the breakthrough study
are presented in Section 4.5.
2.5. Desorption efficiency
The average desorption efficiency for each of the analytes vapor spiked at 0.5, 1 and 2
times the target concentration on ThermoSorb/N air samplers is presented below.
(Section 4.6.)
Average Desorption Efficiency, %
|
NDMA | NDEA | NDPA | NDBA | NPIP | NPYR | NMOR |
|
97.4 | 99.7 | 98.9 | 97.7 | 96.0 | 97.6 | 98.1 |
|
2.6. Recommended air volume and sampling rate
2.6.1. The recommended air volume is 75 L.
2.6.2. The recommended air sampling rate is 1 L/min. Studies indicate that sampling
rates of from 0.2 to 2 L/min may be used.
2.7. Interferences (sampling)
2.7.1. It is imperative, when sampling air for nitrosamines, to be certain that the analyte
is indeed present in the air and not artifactually formed on the sampling device
from precursor amines and nitrosating agents. The commercial ThermoSorb/N
N-nitrosamines air sampler is constructed to prevent the in situ formation of
N-nitrosamines from airborne precursors. The manufacturer has tested the
sampling device for the artifactual formation of NDMA, NPYR, NMOR and diisopropylnitrosamine
using 50 µg each of the respective precursor secondary amines and nitrogen oxides
(NOx). The amines were spiked on the ThermoSorb/N tubes and then
100 L of air containing 0.2, 0.5, 1, 2 or 4 ppm NO/NO2 at a 1/1
ratio was sampled. Various untreated solid adsorbents formed the
N-nitrosamines quite easily but at these levels of amines and
NOx, the ThermoSorb/N cartridges were shown to be
artifact-free (Ref. 5.9.).
The process by which the ThermoSorb/N tubes prevent artifact formation is proprietary.
The manufacturer states that the device has an amine trap that removes incoming amines and
holds them unavailable for nitrosation. The sampled air, after passing through the amine trap,
enters a solid sorbent bed where the N-nitrosamines are quantitatively removed
and retained. The sampled air next passes through fiber pads containing a nitrosation
inhibitor and finally exits the sampler. When the air sampling device is backflushed with
solvent, the nitrosation inhibitor is put into solution and is washed together with the
collected N-nitrosamines and amines into a collection vial. The nitrosation
inhibitor successfully competes with the amine and chemically removes any nitrosating
species (Ref. 5.46.).
The artifact resistance of the ThermoSorb/N air sampler was verified using morpholine
(a precursor amine for NMOR) and nitrogen dioxide. Morpholine was selected as the test amine
because it has been shown to be easily nitrosated. Nitrogen dioxide in a gas bag, mixed with
humid air, has been shown to be an effective nitrosating species. A Teflon gas bag was
prepared containing 33 µg/L morpholine in nitrogen and another containing 4.8 ppm (v/v)
NO2 in air at about 75% relative humidity was also prepared. The
morpholine bag was sampled for 50 min at 1 L/min and then the NO2
bag was sampled for 50 min at 1 L/min. The total morpholine loaded on the tube was 1650 µg.
There was no NMOR formed on the ThermoSorb/N cartridge. The experiment was repeated using a
standard Florisil tube. The result showed that 7 µg of NMOR could be formed, as an
artifact on the tube, after sampling each bag for 7 L.
2.7.2. It is unknown if there are other potential interferences with the collection of N-nitrosamines using ThermoSorb/N cartridges.
2.8. Safety precautions (sampling)
2.8.1. Attach the sampling equipment to the worker in such a manner that it will not interfere with work performance or safety.
2.8.2. Follow all safety practices that apply to the work area to be monitored.
3. Analytical Procedure
3.1. Apparatus
3.1.1. A temperature programmable gas chromatograph (GC).
3.1.2. A high performance liquid chromatographic (HPLC) pump.
3.1.3. An HPLC sample injector.
3.1.4. A Thermal Energy Analyzer (TEA), Thermal Electron Corporation, Waltham, Mass.
3.1.5. A GC column capable of resolving the analytes from each other and potential
interferences. The column used in this work was a 10-ft × 1/8-in. stainless steel
column containing 10% Carbowax 20M with 2% KOH on 80/100 mesh Chromosorb W AW.
3.1.6. A HPLC analytical column capable of resolving the analytes from each other and
potential interferences. The column used in this work was a DuPont Zorbax CN, 4.6 mm × 25 cm.
3.1.7. The necessary hardware to interface the TEA to the GC and the HPLC apparatus.
3.1.8. An electronic integrator or other suitable means to measure peak area and record chromatograms.
3.1.9. Vials, 2-mL with Teflon-lined caps.
3.1.10. Syringes, of convenient sizes for samples and standard preparations and injections.
3.1.11. Hypodermic needles, 23 gauge × 1 in. with a Luer hub.
3.1.12. Volumetric flasks, 1-mL and other convenient sizes.
3.1.13. Dewar flasks, of convenient sizes for liquid nitrogen.
3.1.14. Heating tape, high temperature, heavily insulated.
3.1.15. Variable voltage transformer.
3.2. Reagents
3.2.1. NDMA, NDEA, NDPA, NDBA, NPIP, NPYR and NMOR analytical standards. A certified mixture
containing each of the analytes, in ethanol, at the following concentrations was used to
evaluate this method. The mixture was purchased from and certified by Thermo Electron
Corporation, Waltham, Mass.
Concentrations of the Certified Standard in µg/mL
|
NDMA | NDEA | NDPA | NDBA | NPIP | NPYR | NMOR |
|
10 | 10 | 10 | 9 | 9 | 10 | 15 |
|
3.2.2. Dichloromethane and methanol, HPLC grade. The sample desorption solution is
composed of 75% dichloromethane and 25% methanol by volume.
3.2.3. n-Propanol, acetone and trimethylpentane, HPLC grade.
3.2.4. Nitrogen, liquid.
3.2.5. Helium, GC grade.
3.2.6. Oxygen and air, medical grade.
3.3. Standard preparation
3.3.1. Keep the exposure of the standards to light at a minimum because light will decompose each of the analytes.
3.3.2. In the event that the mixture is not available, dilute the pure individual components
to result in a solution at approximately the following concentrations. Dilute concentrations
higher than 15 µg/mL with ethanol. When the concentration falls below 15 µg/mL,
dilute with the desorbing solution described in Section 3.2.2.
Target Concentrations, µg/mL
|
NDMA | NDEA | NDPA | NDBA | NPIP | NPYR | NMOR |
|
0.20 | 0.20 | 0.20 | 0.18 | 0.18 | 0.20 | 0.30 |
|
The target concentration solution was prepared by diluting the standard mixture
described in Section 3.2.1. 1 to 50 with desorbing solution.
3.3.3. Additional standards at other than the target concentration should be prepared in
order to generate the calibration curve.
3.3.4. Store the standards using well sealed, dark containers in a freezer.
3.4. Sample preparation
3.4.1. Store the samples in a freezer until analysis.
3.4.2. The sample should be received in a foil container. Remove the sample from the container.
3.4.3. Insure that the official OSHA seal is intact and complete.
3.4.4. Check the laboratory sample number against the field identification number to be sure that the sample has been properly identified.
3.4.5. Prepare the desorption solution described in Section 3.2.2. Store the solution in a well sealed, dark bottle.
3.4.6. Label two 1-mL volumetric flasks with the sample number. Further label one flask "A" and the other "B".
3.4.7. Remove the OSHA seal and the red end caps from the sample.
3.4.8. Attach a syringe needle to the male Luer fitting at the inlet port of the air sampler.
3.4.9. Fill a syringe with about 4 mL of the desorption solution. Attach the syringe to the female Luer fitting located at the outlet end of the air sampler.
3.4.10. Elute the sample by gently forcing the desorption solvent through the air sampler at approximately
0.5 mL/min. Collect the first 1-mL portion of solvent in the volumetric flask labeled "A"
in Section 3.4.6. and the second 1-mL of eluent in the flask labeled "B".
3.4.11. Because light will decompose N-nitrosamines, it is necessary to prevent exposure of the eluted samples to light.
3.4.12. If the eluted samples are not to be analyzed immediately, transfer the contents of each flask to a separate vial
which can be sealed with a Teflon-lined cap. Protect the samples from light and store them in a freezer.
3.5. Analysis
3.5.1. Instrument conditions
GC conditions | |
injector temperature: | 150°C |
column temperature: | 150 to 200°C at 4°C/min |
transfer line temp.: | 210°C |
helium (carrier gas): | 30 mL/min |
injection volume: | 5 µL |
The recommended GC column is a 10-ft × 1/8-in. stainless steel
column packed with 10% Carbowax 20M with 2% KOH on 80/100 mesh Chromosorb W AW. |
TEA conditions |
GC pyrolyzer temp.: | 475°C |
oxygen: | 5 mL/min |
pressure: | 1 mm Hg |
attenuation: | 4 |
cold trap temp.: | -130°C (n-propanol and liquid nitrogen) |
3.5.2. The transfer line between the GC and the TEA must be maintained at about 210°C.
The use of a heating tape and a variable voltage transformer is recommended.
3.5.3. Chromatogram (Figure 4.3.1.)
3.5.4. Detector response is measured with an electronic integrator or other suitable means.
3.5.5. An external standard procedure is used to prepare a calibration curve using at
least three standard solutions of different concentrations. The calibration curve
is prepared daily. The integrator is calibrated to report results in µg/mL.
3.5.6. Bracket the samples with analytical standards.
3.6. Interferences (analytical)
3.6.1. Because the TEA has been shown to respond to compounds other than N-nitrosamines
(Ref. 5.47.), it is strongly recommended that positive GC/TEA results be
confirmed by HPLC/TEA analysis. Since GC and HPLC separation techniques operate using different
principles, the component elution order is not the same. It is unlikely that two different
compounds will have a coincidence of retention time on both GC and HPLC columns.
HPLC conditions for confirmation of high samples
column: | DuPont Zorbax CN (4.6 mm × 25 cm) |
mobile phase: | 95% trimethylpentane/ 5% acetone, v/v |
flow rate: | 1.3 mL/min |
injection volume: | 5 to 25 µL |
The TEA conditions are the same as for the GC/TEA analysis except that the HPLC pyrolyzer is
used at 550°C and the cold trap is maintained at -80°C with a mixture
of water, n-propanol and liquid nitrogen.
3.6.2. GC and HPLC parameters may be changed to circumvent interferences. Possible
interferences are listed on the sample data sheets.
3.6.3. The only unequivocal means of structure designation is by high resolution mass
spectrometry with continuous peak matching. It is recommended this procedure
be used to confirm samples whenever possible.
3.7. Calculations
3.7.1. The integrator value in µg/mL is used for reference only. More reliable results
are obtained by use of a calibration curve. The detector response, for each standard, is
compared to its equivalent concentration in µg/mL and the best straight line through the data
points is determined by linear regression.
3.7.2. The concentration, in µg/mL, for a particular determination is obtained by comparing
its detector response to the calibration curve.
3.7.3. The result obtained from the analysis of each vial or flask is corrected by the
appropriate desorption efficiency, and then the corrected results from the "A" and
"B" determinations that compose a particular air sample are added together.
3.7.4. The air concentrations for a sample result is calculated by the following equation:
µg/m3 = (C)(D)(1000) / E
where C = D = E = |
µg/mL from Section 3.7.3.
desorption volume in milliliters (1 mL)
air volume in liters |
3.7.5. To correct the results from Section 3.7.4. to parts-per-billion the following relationship is used:
ppb = (µg/m3)(24.46) / MW
where |
µg/m3 = |
result from Section 3.7.4. |
| 24.46 = | molar volume of an ideal gas at 25°C and 760 mm Hg. |
| MW = | molecular weight of the analyte, obtained below. |
Molecular Weights of the Analytes
|
NDMA | NDEA | NDPA | NDBA | NPIP | NPYR | NMOR |
|
74.08 | 102.14 | 130.19 | 158.2 | 114.15 | 100.0 | 116.1 |
|
3.8. Safety precautions (analytical)
3.8.1. The analytes are extremely potent animal carcinogens and utmost care must be exercised when working with these compounds.
3.8.2. Avoid skin contact with liquid nitrogen and the solvents.
3.8.3. Confine the use of solvents to a fume hood.
3.8.4. Wear safety glasses in all laboratory areas.
3.8.5. Check to be sure that the TEA exhaust is connected to a fume hood.
4. Backup Data
4.1. Detection limit of the analytical procedure
Figure 4.1. is a chromatogram obtained from a 5-µL
injection of a standard solution at the following concentrations.
Table 4.1. The Concentrations of the Detection Limit Standard in µg/mL.
|
NDMA | NDEA | NDPA | NDBA | NPIP | NPYR | NMOR |
|
0.01 | 0.01 | 0.01 | 0.009 | 0.009 | 0.01 | 0.015 |
|
4.2. The detection limit of the overall procedure and the reliable quantitation limit.
The following data were obtained by vapor spiking the analytes on air samplers.
Table 4.2. Desorption Efficiencies at the Detection Limit
|
analyte ng/sample |
NDMA 10 |
NDEA 10 |
NDPA 10 |
NDBA 9 |
NPIP 9 |
NPYR 10 |
NMOR 15 |
|
recovery, % |
91.0 101.2 102.7 104.4 109.5 108.1 |
107.2 116.5 99.5 112.7 108.4 112.0 |
90.1 90.4 93.3 101.3 103.8 96.2 |
113.2 96.0 98.3 119.5 100.8 104.7 |
95.4 94.7 95.0 103.2 102.2 92.4 |
83.5 81.0 79.1 98.1 94.6 96.7 |
103.1 98.1 85.5 101.0 90.9 86.0 |
|
![mean](https://webarchive.library.unt.edu/eot2008/20081106071640im_/http://www.osha.gov/dts/sltc/methods/images/mean.gif) SD 1.96 SD |
102.8 6.593 12.9 |
109.4 5.864 11.5 |
95.8 5.697 11.2 |
105.4 9.166 18.0 |
97.2 4.435 8.7 |
88.8 8.550 16.8 |
94.1 7.674 15.0 |
|
4.3. Precision of the analytical procedure
The following data were obtained from multiple injections of analytical standards.
Table 4.3.1. 0.5 × Target Concentration
|
analyte µg/mL |
NDMA 0.10 |
NDEA 0.10 |
NDPA 0.10 |
NDBA 0.090 |
NPIP 0.090 |
NPYR 0.10 |
NMOR 0.15 |
|
area counts |
25396 26599 24888 24455 27643 |
20623 22521 23689 21599 20024 |
16848 18318 17322 17349 16197 |
11244 11693 11788 12042 12855 |
16015 16543 14112 15843 15714 |
20051 19715 18453 19972 17380 |
26683 26215 28041 27430 26656 |
|
![mean](https://webarchive.library.unt.edu/eot2008/20081106071640im_/http://www.osha.gov/dts/sltc/methods/images/mean.gif) SD CV (%) |
25796.2 1307.57 5.07 |
21691.2 1467.04 6.76 |
17206.8 777.28 4.52 |
11924.4 594.76 4.99 |
15645.4 913.42 5.84 |
19114.2 1163.94 6.09 |
27005.0 725.17 2.69 |
|
Table 4.3.2. 1 × Target Concentration
|
analyte µg/mL |
NDMA 0.20 |
NDEA 0.20 |
NDPA 0.20 |
NDBA 0.18 |
NPIP 0.18 |
NPYR 0.20 |
NMOR 0.30 |
|
area counts |
49510 50742 47671 47182 51124 |
43828 42661 40916 40588 43604 |
28483 32234 29839 28192 32308 |
20855 24048 23085 21746 23588 |
29517 33733 32097 32614 34985 |
37646 38898 38797 39735 39681 |
56148 52347 53250 55774 56741 |
|
![mean](https://webarchive.library.unt.edu/eot2008/20081106071640im_/http://www.osha.gov/dts/sltc/methods/images/mean.gif) SD CV (%) |
49245.8 1773.08 3.60 |
42319.4 1500.84 3.55 |
30211.2 1980.57 6.56 |
22664.4 1328.69 5.86 |
32589.2 2045.08 6.28 |
38951.4 848.10 2.18 |
54852.0 1932.58 3.52 |
|
Table 4.3.3. 2 × Target Concentration
|
analyte µg/mL |
NDMA 0.40 |
NDEA 0.40 |
NDPA 0.40 |
NDBA 0.36 |
NPIP 0.36 |
NPYR 0.40 |
NMOR 0.60 |
|
area counts |
97764 97759 96497 100393 95827 |
84833 82918 83760 84837 84281 |
63298 64629 65206 67017 67276 |
45551 46465 46143 46978 48762 |
61866 64343 64646 64918 65845 |
80671 77716 81891 77044 80412 |
104244 109657 108013 101980 109832 |
|
![mean](https://webarchive.library.unt.edu/eot2008/20081106071640im_/http://www.osha.gov/dts/sltc/methods/images/mean.gif) SD CV (%) |
97648.0 1746.54 1.79 |
84125.8 809.72 0.96 |
65485.2 1669.45 2.55 |
46779.8 1223.00 2.61 |
64323.6 1484.26 2.31 |
79546.8 2069.03 2.60 |
106745.2 3484.87 3.26 |
|
Table 4.3.4. The Pooled Coefficients of Variation
|
NDMA | NDEA | NDPA | NDBA | NPIP | NPYR | NMOR |
|
0.037 | 0.044 | 0.048 | 0.047 | 0.051 | 0.040 | 0.032 |
|
4.4. Sensitivity
The data in Tables 4.3.1. - 4.3.3. are presented respectively in Figures 4.4.1. - 4.4.7.
4.5. Breakthrough
The breakthrough study was conducted by first vapor-spiking the following amounts of
the analytes on the first of two ThermoSorb/N tubes connected in series.
Table 4.5.1. Amounts of Analyte Used in Breakthrough Studies
|
analyte | NDMA | NDEA | NDPA | NDBA | NPIP | NPYR | NMOR |
|
µg |
0.40 | 0.40 | 0.40 | 0.36 | 0.36 | 0.40 | 0.60 |
|
Next, air at about 80% relative humidity and 22°C was drawn through the sampling train. After
the appropriate air volume had been sampled, both tubes were analyzed and the results are presented in Table 4.5.2.
Table 4.5.2. Breakthrough Study
|
air vol. | flow rate | % breakthrough |
(L) | (L/min) | NDMA | NDEA | NDPA | NDBA | NPIP | NPYR | NMOR |
|
80 88 93 120 128a 280b 400c |
1.0 0.2 2.0 1.0 1.0 1.0 2.0 |
0 4.3 0 16.0 19.2 93.7 100.0 |
0 0 0 0 - 0 0 |
0 0 0 0 - 0 0 |
0 0 0 0 - 0 0 |
0 0 0 0 - 0 0 |
0 0 0 0 - 0 0 |
0 0 0 0 - 0 0 |
|
a This run (with NDMA only) was made to determine if the presence of the other analytes had an effect on the breakthrough for NDMA.
b NDMA lost from the first tube was recovered in the second tube.
c About 16% of the NDMA vapor-spiked was lost from the system.
4.6. Desorption efficiency (vapor-spiked)
Table 4.6.1. Desorption Efficiency at 0.5× the Target Concentration
|
analyte µg/sample |
NDMA 0.10 |
NDEA 0.10 |
NDPA 0.10 |
NDBA 0.09 |
NPIP 0.09 |
NPYR 0.10 |
NMOR 0.15 |
|
% recovered |
100.53 92.10 93.20 92.65 100.67 94.88 |
99.10 95.50 98.08 101.77 95.58 100.48 |
99.70 96.40 95.95 98.04 96.83 97.91 |
95.24 93.73 96.24 92.65 101.03 100.00 |
92.33 95.15 93.20 92.86 100.00 94.57 |
93.19 93.19 91.43 94.09 96.05 101.97 |
92.33 94.07 94.36 101.81 96.92 100.15 |
|
![mean](https://webarchive.library.unt.edu/eot2008/20081106071640im_/http://www.osha.gov/dts/sltc/methods/images/mean.gif) |
95.67 | 98.42 | 97.47 | 96.48 | 94.68 | 94.99 | 96.61 |
|
Table 4.6.2. Desorption Efficiency at the Target Concentration
|
analyte µg/sample |
NDMA 0.20 |
NDEA 0.20 |
NDPA 0.20 |
NDBA 0.18 |
NPIP 0.18 |
NPYR 0.20 |
NMOR 0.30 |
|
% recovered |
106.84 98.19 96.60 92.10 103.59 96.50 |
107.49 99.16 102.40 107.00 96.45 94.32 |
101.00 102.68 103.43 96.00 104.50 95.91 |
102.03 101.82 101.60 96.89 103.33 99.86 |
98.45 101.46 98.45 96.67 93.06 95.37 |
99.28 100.00 96.73 93.00 97.92 99.11 |
100.87 101.03 97.48 100.18 97.67 94.16 |
|
![mean](https://webarchive.library.unt.edu/eot2008/20081106071640im_/http://www.osha.gov/dts/sltc/methods/images/mean.gif) |
98.97 | 101.14 | 100.59 | 100.92 | 97.24 | 97.67 | 98.56 |
|
Table 4.6.3. Desorption Efficiency at 2× the Target Concentration
|
analyte µg/sample |
NDMA 0.40 |
NDEA 0.40 |
NDPA 0.40 |
NDBA 0.36 |
NPIP 0.36 |
NPYR 0.40 |
NMOR 0.60 |
|
% recovered |
95.78 99.22 97.21 94.15 99.22 98.99 |
100.51 101.33 95.37 99.02 100.62 100.32 |
98.46 100.00 98.41 99.39 97.54 98.16 |
95.20 97.11 98.50 94.66 94.22 94.36 |
96.58 99.14 96.01 94.15 95.76 94.15 |
98.77 100.56 97.88 100.99 101.36 101.36 |
96.14 99.72 100.80 95.76 100.37 101.34 |
|
![mean](https://webarchive.library.unt.edu/eot2008/20081106071640im_/http://www.osha.gov/dts/sltc/methods/images/mean.gif) |
97.43 | 99.53 | 98.66 | 95.68 | 95.96 | 100.15 | 99.02 |
|
Table 4.6.4
Average Desorption Efficiency Over the Range of From 0.5× to 2× the Target Concentration
|
analyte | NDMA | NDEA | NDPA | NDBA | NPIP | NPYR | NMOR |
|
% | 97.4 | 99.7 | 98.9 | 97.7 | 96.0 | 97.6 | 98.1 |
|
4.7. Storage test
The data in Tables 4.7.2. and 4.7.3. represent the effects of storage at ambient (21 to
26°C) and reduced (-20°C) temperatures on the analytes vapor spiked
on ThermoSorb/N tubes at the following levels.
Table 4.7.1. Amounts of Analyte Used in Storage Tests
|
analyte | NDMA | NDEA | NDPA | NDBA | NPIP | NPYR | NMOR |
|
µg | 0.20 | 0.20 | 0.20 | 0.18 | 0.18 | 0.20 | 0.30 |
|
The recoveries are not corrected for desorption efficiency. Three stored samples were
analyzed at approximately three-day intervals. Graphical representations of the
data may be found in Figures 4.7.1. to 4.7.14.
Table 4.7.2. Ambient Temperature Storage Test (% Recovered)
|
days of storage | NDMA | NDEA | NDPA | NDBA | NPIP | NPYR | NMOR |
|
0 3 7 10 14 17 |
94.0 99.7 100.2 95.8 97.2 99.0 98.5 102.4 93.9 95.7 97.0 103.2 93.5 96.3 94.1 92.3 91.5 93.2 |
97.0 104.2 102.0 98.9 92.7 95.8 96.6 100.9 100.5 96.2 96.8 108.2 95.0 99.3 96.3 97.6 96.9 100.1 |
97.2 104.0 102.1 94.3 97.4 92.6 101.0 97.2 98.0 99.0 92.6 104.0 89.0 93.8 93.1 92.2 92.8 92.4 |
96.2 99.4 98.6 96.4 91.0 93.7 92.1 100.7 99.1 92.4 89.1 97.7 83.5 88.9 87.8 91.4 88.9 89.7 |
94.8 101.9 99.0 94.2 93.0 95.2 94.6 93.6 96.6 93.6 90.0 99.3 89.0 89.2 86.0 89.4 90.2 89.3 |
94.8 100.4 95.3 91.5 88.2 91.9 90.6 89.7 93.0 85.9 85.4 94.8 86.0 86.3 84.3 86.0 85.6 84.9 |
92.4 99.3 95.0 89.5 89.6 97.9 90.3 92.1 99.9 96.2 90.8 97.7 88.0 88.8 85.1 90.2 89.7 89.8 |
|
Table 4.7.3. Reduced Temperature Storage Test (% Recovered)
|
days of storage | NDMA | NDEA | NDPA | NDBA | NPIP | NPYR | NMOR |
|
0 3 7 10 14 17 |
96.4 95.8 94.3 95.2 96.5 97.7 101.4 99.9 99.5 103.0 99.5 99.7 101.6 105.1 100.3 99.6 95.4 97.3 |
100.4 99.4 96.6 106.0 98.5 101.1 100.3 99.4 100.5 105.3 103.2 100.1 103.5 101.6 103.1 101.4 97.1 100.5 |
99.1 94.6 93.1 105.7 98.2 100.2 100.0 97.5 97.8 101.2 101.9 97.5 104.8 100.8 100.7 97.6 92.2 100.1 |
100.6 95.1 97.0 101.2 95.1 97.6 92.6 93.3 94.1 94.7 102.6 96.2 107.5 99.2 100.1 99.7 96.4 96.1 |
97.8 95.0 94.2 100.4 94.3 95.4 97.1 96.3 97.3 101.9 99.1 94.5 101.0 96.3 100.8 101.6 96.4 95.9 |
91.5 90.9 89.5 97.9 95.0 93.0 96.7 92.6 92.3 91.4 94.8 89.0 96.7 86.8 94.1 94.7 92.5 89.3 |
94.5 95.2 90.6 98.8 91.2 93.5 96.0 90.2 94.9 94.7 94.3 90.2 94.8 89.5 93.0 94.1 92.5 98.3 |
|
4.8. Toxic effects (This section is for information only and should not be taken as the basis of OSHA policy).
NDMA
The LD50 for NDMA, administered orally to the rat, is 26 mg/kg.
The LC50 is 78 ppm following an exposure time of four hours
(Ref. 5.13.). NDMA is carcinogenic to many different animal species. The agent is carcinogenic following prenatal exposure and in single dose experiments (<A HREF=" #ref514" title="See Reference 5.14" >Ref. 5.14). When 4 mg/kg of NDMA was administered in the drinking
water 5 times a week to 20 rats, liver cancer was detected in 13 of the animals. The mean
total dose which was applied until the appearance of malignant tumors in 50% of the animals
(D50) was 0.4 g/kg and the mean tumor induction period in days
(t50) was 270 days. In an inhalation experiment, six rats were
exposed to 4 mg/kg NDMA for 1/2 hour two times a week. Four rats died because of cancer of
the posterior nasal cavity which had entered the cranial cavity. One rat had cancer of the
pituitary gland and the last animal had a kidney tumor. There were no liver tumors. The
D50 was 0.25 g/kg and the t50 was 400
days. The inhalation experiment was repeated at 2 mg/kg using 12 rats. Three rats died
prematurely and a fourth without tumors. The remaining 8 animals died from cancer of the
posterior nasal cavity. Again, there were no liver tumors. The D50
was lower than for the high dose at 0.14 g/kg and the t50 was
shorter at 340 days (Ref. 5.12.). NDMA has been shown to cause cancer
in the rat, mouse, Syrian Golden and European hamsters, mastomys, guinea pig, rainbow trout,
newt, aquarium fish and mink. The principal affected organs were the liver, lung, nasal
cavities and kidney (Ref. 5.15). It is known that chronic exposure to
NDMA causes severe liver damage and cirrhosis in man (Ref. 5.15).
It has been reported that both rat and human liver slices metabolize NDMA in a similar manner
(Ref. 5.14).
NDEA
The LD50 for NDEA is 280 mg/kg after oral administration to the rat
(Ref. 5.13.). The agent is carcinogenic to many different animal
species which include sub-human primates. NDEA induces cancer following prenatal exposure and
in single dose experiments (Ref. 5.14.). NDEA was administered to rats
in drinking water in a chronic exposure experiment. Daily exposure was between 0.075 and
14.2 mg/kg in nine groups of animals. The total dose, until death occurred, was between
64 and 965 mg/kg. The tumor induction time was between 68 and 840 days. All daily doses
higher than 0.15 mg/kg gave a tumor incidence of 100%. When a dose of 0.15 mg/kg per day was
administered, a tumor yield of 90% was obtained. At 0.075 mg/kg per day, 20 rats survived for
more than 600 days and 11 of the 20 animals had tumors of the liver, esophagus, or the nasal
cavity. All four of the animals that lived longer than 940 days at this dose level had tumors.
The location of the tumors was dependent on the dose given, the non-liver tumors
evolved only if cancer of the liver had not caused death. NDEA has proven to be a stronger
carcinogen than NDMA even though the LD50 for NDMA is much lower
(Ref. 5.12.). NDEA has been shown to cause cancer in the rat, African
white-tailed rat, mouse, Syrian Golden, Chinese and European hamsters, guinea
pig, rabbit, parakeet and monkey. The principal affected organs were the liver, esophagus,
nasal cavities, kidney, forestomach, lung and larynx (Ref. 5.15).
NDPA
The LD50 for NDPA, administered orally to the rat, is 480 mg/kg
(Ref. 5.13.). In a chronic experiment, the agent was added to the
daily food of the rats. Four dose groups were involved - 30 mg/kg led to cancer of the liver,
15 mg/kg produced liver cancer in all the dosed rats and in four cases metastases into the
lung was observed. When 8 mg/kg NDPA was administered, the result was cancer in 15 of 16
animals. The lowest dose, 4 mg/kg, resulted in cancer of the liver in 12 of 14 animals. The
mean carcinogenic doses (D50) were 3.2, 1.86, 1.52 and 1.15 g/kg.
The mean induction periods (t50) were 120, 155, 202 and 300 days.
(Ref. 5.12.).
NDBA
The LD50 for NDBA, following oral administration to the rat, is
1200 mg/kg (Ref. 5.13.). When NDBA was given in the food - 75 mg/kg
caused liver tumors together with cirrhosis in all the rats, 37.5 mg/kg resulted in liver
cancer without cirrhosis in 13 of 16 rats. Five animals had cancer of the esophagus and
five cancer of the urinary bladder. Another group of rats received daily doses of 20 mg/kg
and the results were multiple cancers of the esophagus in eight rats, seven bladder cancers
and four animals with liver cancer. A daily dose of 10 mg/kg produced liver cancer in one
animal and two adenomas in a total of ten treated animals. NDBA was the only
N-nitrosamines of the 65 tested which produced tumors of the urinary bladder
and the agent was particularly effective following subcutaneous injection
(Ref. 5.12.). NDBA has been shown to cause cancer in the rat, mouse,
Syrian Golden and Chinese hamsters and guinea pig. The principal organs affected were the
bladder, esophagus, liver forestomach, tongue and lung (Ref. 5.15).
NPIP
The LD50 for NPIP, after oral administration to the rat, is
200 mg/kg (Ref. 5.12). When 20 mg/kg was given to rats in the daily
drinking water, 17 of 20 rats died prematurely. Three rats died after 186, 232 and 289
days of liver cancer with metastases in the lungs, the last animal also had cancer in
the esophagus. Because the 20 mg/kg daily dose was not tolerated well, the experiment was
repeated at 5 mg/kg. Of nine animals, one died with papillomas, the other eight died of
esophageal cancer. Three rats also had liver cancer. The mean carcinogen dose was 1.4 g/kg.
and the average induction period was 280 days (Ref. 5.12.). NPIP has
produced cancer in the rat, mouse, Syrian Golden hamster and monkey. The principal affected
organs were the esophagus, liver, nasal cavities, larynx, trachea and forestomach
(Ref. 5.15).
NPYR
The LD50 for NPYR, administered orally to the rat, is 900 mg/kg
(Ref. 5.12). In chronic experiments, 10 mg/kg and 5 mg/kg were
administered in the daily drinking water to two groups of five and 20 rats. Because the
carcinogenic effect was weak, the dose was doubled after 150 days. All the animals, but two
who died without tumors, developed liver cancer. The average carcinogenic doses
(D50) were 4.2 and 3.9 g/kg and the mean induction periods
(t50) were 290 and 470 days. The agent was determined to be a weak
but relatively certain carcinogen (Ref. 5.12.). NPYR has produced cancer
in the rat, mouse and Syrian Golden hamster. The principal affected areas were the liver, nasal
cavities, testes, lung and trachea (Ref. 5.15).
NMOR
The LD50 for NMOR, after oral administration to the rat, was 320 mg/kg
(Ref. 5.12). When 16 rats were given 8 mg/kg NMOR daily in the drinking water,
14 animals died of liver cancer. The mean induction period (t50) was
only 165 days. A dose of 16 mg/kg caused liver tumors in two of four rats after only 45 and 65
days respectively and after 115 days liver cancer was observed. NMOR was clearly the most rapidly
acting liver carcinogen of the 65 N-nitroso compounds tested
(Ref. 5.12.). NMOR has produced cancer in the rat, mouse, and Syrian Golden
hamster. The principal affected organs were the liver, nasal cavities, kidney, esophagus, ovary,
trachea, larynx and bronchi (Ref. 5.15).
![The metabolic activation on N-nitrosokialkylamines](https://webarchive.library.unt.edu/eot2008/20081106071640im_/http://www.osha.gov/dts/sltc/methods/organic/org027/org27fig01.gif)
Figure 1.1.2. The metabolic activation on N-nitrosokialkylamines.
![The molecular structures of the analytes](https://webarchive.library.unt.edu/eot2008/20081106071640im_/http://www.osha.gov/dts/sltc/methods/organic/org027/org27fig02.gif)
Figure 1.1.4 The molecular structures of the analytes.
|
|
PEAK | PEAK ID | AMOUNT, Pg. |
|
1 2 3 4 5 6 7 |
NDMA NDEA NDPA NDBA NPIP NPYR NMOR |
50 50 50 45 45 50 75 |
|
|
Figure 4.1. The detection limits of the analytical procedure.
|
|
|
| PEAK IDENTIFICATION | CONCENTRATION µg/mL |
|
1 2 3 4 5 6 7 |
NDMA NDEA NDPA NDBA NPIP NPYR NMOR |
0.20 0.20 0.20 0.18 0.18 0.20 0.30 |
|
|
Figure 4.3.1. GC/TEA chromatogram of the analytes.
|
|
|
| PEAK IDENTIFICATION | CONCENTRATION µg/mL |
|
1 2 3 4 5 6 7 |
NDMA NDEA NDPA NDBA NPIP NPYR NMOR |
0.18 0.20 0.20 0.18 0.20 0.30 0.20 |
|
|
Figure 4.3.2. HPLC/TEA chromatogram of the analytes.
|
![Calibration curve for N-nitrosodimethylamine](https://webarchive.library.unt.edu/eot2008/20081106071640im_/http://www.osha.gov/dts/sltc/methods/organic/org027/org27fig06.gif)
Figure. 4.4.1. Calibration curve for N-nitrosodimethylamine.
![Calibration curve for N-nitrosodiethylamine](https://webarchive.library.unt.edu/eot2008/20081106071640im_/http://www.osha.gov/dts/sltc/methods/organic/org027/org27fig07.gif)
Figure 4.4.2. Calibration curve for N-nitrosodiethylamine.
![Calibration curve for N-nitrosodipropylamine](https://webarchive.library.unt.edu/eot2008/20081106071640im_/http://www.osha.gov/dts/sltc/methods/organic/org027/org27fig08.gif)
Figure 4.4.3. Calibration curve for N-nitrosodipropylamine.
![Calibration curve for N-nitrosodibutylamine](https://webarchive.library.unt.edu/eot2008/20081106071640im_/http://www.osha.gov/dts/sltc/methods/organic/org027/org27fig09.gif)
Figure 4.4.4. Calibration curve for N-nitrosodibutylamine.
![Calibration curve for N-nitrosopiperdine.](https://webarchive.library.unt.edu/eot2008/20081106071640im_/http://www.osha.gov/dts/sltc/methods/organic/org027/org27fig10.gif)
Figure 4.4.5. Calibration curve for N-nitrosopiperdine.
![Calibration curve for N-nitrosopyrrolidine](https://webarchive.library.unt.edu/eot2008/20081106071640im_/http://www.osha.gov/dts/sltc/methods/organic/org027/org27fig11.gif)
Figure 4.4.6. Calibration curve for N-nitrosopyrrolidine.
![Calibration curve for N-nitrosomorpholine](https://webarchive.library.unt.edu/eot2008/20081106071640im_/http://www.osha.gov/dts/sltc/methods/organic/org027/org27fig12.gif)
Figure 4.4.7. Calibration curve for N-nitrosomorpholine.
![Ambient temperature storage test for N-nitrosodimethylamine](https://webarchive.library.unt.edu/eot2008/20081106071640im_/http://www.osha.gov/dts/sltc/methods/organic/org027/org27fig13.gif)
Figure 4.7.1. Ambient temperature storage test for N-nitrosodimethylamine.
![Ambient temperature storage test for N-nitrosodiethylamine](https://webarchive.library.unt.edu/eot2008/20081106071640im_/http://www.osha.gov/dts/sltc/methods/organic/org027/org27fig14.gif)
Figure 4.7.2. Ambient temperature storage test for N-nitrosodiethylamine.
![Ambient temperature storage test for N-nitrosodipropylamine](https://webarchive.library.unt.edu/eot2008/20081106071640im_/http://www.osha.gov/dts/sltc/methods/organic/org027/org27fig15.gif)
Figure 4.7.3. Ambient temperature storage test for N-nitrosodipropylamine.
![Ambient temperature storage test for N-nitrosodibutylamine](https://webarchive.library.unt.edu/eot2008/20081106071640im_/http://www.osha.gov/dts/sltc/methods/organic/org027/org27fig16.gif)
Figure 4.7.4. Ambient temperature storage test for N-nitrosodibutylamine.
![Ambient temperature storage test for N-nitrosopiperdine](https://webarchive.library.unt.edu/eot2008/20081106071640im_/http://www.osha.gov/dts/sltc/methods/organic/org027/org27fig17.gif)
Figure 4.7.5. Ambient temperature storage test for N-nitrosopiperdine.
![Ambient temperature storage test for N-nitrosopyrrolidine](https://webarchive.library.unt.edu/eot2008/20081106071640im_/http://www.osha.gov/dts/sltc/methods/organic/org027/org27fig18.gif)
Figure 4.7.6. Ambient temperature storage test for N-nitrosopyrrolidine.
![Ambient temperature storage test for N-nitrosomorpholine](https://webarchive.library.unt.edu/eot2008/20081106071640im_/http://www.osha.gov/dts/sltc/methods/organic/org027/org27fig19.gif)
Figure 4.7.7. Ambient temperature storage test for N-nitrosomorpholine.
![Reduced temperature storage test for N-nitrosodimethylamine](https://webarchive.library.unt.edu/eot2008/20081106071640im_/http://www.osha.gov/dts/sltc/methods/organic/org027/org27fig20.gif)
Figure 4.7.8. Reduced temperature storage test for N-nitrosodimethylamine.
![Reduced temperature storage test for N-nitrosodiethylamine](https://webarchive.library.unt.edu/eot2008/20081106071640im_/http://www.osha.gov/dts/sltc/methods/organic/org027/org27fig21.gif)
Figure 4.7.9. Reduced temperature storage test for N-nitrosodiethylamine.
![Reduced temperature storage test for N-nitrosodipropylamine](https://webarchive.library.unt.edu/eot2008/20081106071640im_/http://www.osha.gov/dts/sltc/methods/organic/org027/org27fig22.gif)
Figure 4.7.10. Reduced temperature storage test for N-nitrosodipropylamine.
![Reduced temperature storage test for N-nitrosodibutylamine](https://webarchive.library.unt.edu/eot2008/20081106071640im_/http://www.osha.gov/dts/sltc/methods/organic/org027/org27fig23.gif)
Figure 4.7.11. Reduced temperature storage test for N-nitrosodibutylamine.
![Reduced temperature storage test for N-nitrosopiperidine](https://webarchive.library.unt.edu/eot2008/20081106071640im_/http://www.osha.gov/dts/sltc/methods/organic/org027/org27fig24.gif)
Figure 4.7.12. Reduced temperature storage test for N-nitrosopiperidine.
![Reduced temperature storage test for N-nitrosopyrrolidine](https://webarchive.library.unt.edu/eot2008/20081106071640im_/http://www.osha.gov/dts/sltc/methods/organic/org027/org27fig25.gif)
Figure 4.7.13. Reduced temperature storage test for N-nitrosopyrrolidine.
![Reduced temperature storage test for N-nitrosomorpholine](https://webarchive.library.unt.edu/eot2008/20081106071640im_/http://www.osha.gov/dts/sltc/methods/organic/org027/org27fig26.gif)
Figure 4.7.14. Reduced temperature storage test for N-nitrosomorpholine.
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