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Aniline
Related Information: Chemical Sampling -
Aniline
|
Method no.: |
PV2079 |
|
Control no.: |
T-PV2079-01-9406-CH |
|
Matrix |
Air |
|
Target concentration: |
5 ppm (19 mg/m³) (OSHA PEL) |
|
Procedure: |
Samples are collected by drawing a known volume of air
through an acid coated XAD-7 tube. Samples are desorbed with of
methanol containing 0.2 N ammonium hydroxide (NH4OH) and
analyzed by gas chromatography (GC) using a flame ionization
detector. |
|
Recommended air volume and sampling
rate: |
30 liters (L) at 0.2 L/min |
|
Reliable quantitation limit: |
0.02 ppm (0.09 mg/m3) |
|
Status of method: |
Partially Evaluated Method. This method has been
subjected to established evaluation procedures, and is presented for
information and trial use. |
|
June 1994 |
Duane Lee |
Organic Service Branch II OSHA Salt Lake Technical
Center Salt Lake City, UT 84165-1802 |
1. General Discussion
1.1 Background
1.1.1 History
Information had been received from the National Institute of
Occupational Safety and Health (NIOSH) that there were some
deficiencies in the NIOSH method for aniline. (Ref. 5.1) It was noted
that desorption efficiencies at low levels had not been tested and
that the stability of samples for longer that 1 week was not known.
Because of these concerns, the desorption, retention and stability of
aniline on silica gel tubes was tested.
A desorption study was done on silica gel tubes by spiking tubes at
0.5, 1.0, and 2.0 times the PEL. These were allowed to equilibrate
overnight and the next day desorbed and analyzed. The recoveries over
the range was 96%. This was followed by a retention study where tubes
were spiked at 2.0 times the PEL, allowed to equilibrate overnight, 30
L of humid air drawn through each tube and then analyzed. The average
recovery was 3.9%. This did not indicate that silica gel tubes had a
good retention of aniline under humid conditions. The interference
effects of water vapor on the collection of aniline on silica gel
tubes has been addressed previously. (Ref. 5.2)
Since collection on silica gel was not adequate, the sulfuric acid
(H2SO4) coated glass fiber filters were tested
because the method for toluidine uses these filters. A desorption
study at 0.1, 0.5, 1.0 and 2.0 times the PEL was done. The average
recovery over the range was 97%. This was followed by a retention
study where the acid coated filters were spiked at 2.0 x the PEL and
allowed to equilibrate overnight. The next day 100 L of humid air were
drawn through each filter and then analyzed. The average recovery was
82%. Silica gel did not yield a satisfactory retention efficiency.
A collection media that has been tested for some of the more
volatile amines was tried next. The media is a 10% phosphoric acid
(H3PO4) coated XAD-7 tube and gave good
preliminary results. This report describes the analytical method
developed for the sampling and analysis of aniline using this
collection media.
1.1.2 Toxic effects (This section is for information only and
should not be taken as the basis of OSHA policy.)
Aniline is toxic and can be absorbed through the skin and by
inhalation. At one time, the over-exposure resulting in aniline
poisoning was common. The poisoning is due to the conversion of
hemoglobin to methemoglobin which does not release oxygen to the
tissues and results in cyanosis and possible death from asphyxiation.
(Ref. 5.3 and 5.4)
The acute oral LD50 of 0.44 g/kg has been reported for
rats. (Ref. 5.4)
Studies have been done on animals for evidence of carcinogenicity.
The results of the studies are limited and most results are negative.
(Ref. 5.5)
Studies have been done on workers in the aniline-dye industry. The
results from these studies attribute cancer deaths to chemicals other
than aniline. (Ref. 5.6)
1.1.3 Workplace exposure
Aniline is used as a parent substance in the manufacture of several
chemical products and intermediates. The major uses are in the
production of polymers (isocyanates), rubber chemicals, dyes,
hydroquinone, drugs, agriculture and miscellaneous applications. (Ref.
5.3) In 1979, the total production of eight companies in the United
States amounted to 313 million kilograms and imports totaled 19,657
kilograms. (Ref. 5.5) There was no information available on the number
of workers exposed to aniline.
1.1.4 Physical properties and other descriptive information (Ref.
5.3 unless otherwise indicated)
Synonyms: |
Benzenamine |
CAS number: |
62-53-3 |
IMIS: |
0220 |
RTECS: |
BW6650000; 8036 (Ref. 5.7) |
DOT: |
UN1547 |
Vapor pressure: |
6.67 kPa (50 mmHg) at 102ºC |
Molecular weight: |
93.1 |
Flash point: |
76ºC (169ºF) (closed-cup) |
Boiling point: |
184.4ºC |
Melting point: |
-6.15ºC |
Color: |
colorless when fresh, darkens on exposure to air
and light |
Density: |
1.022 |
Molecular formula: |
C6H7N |
Structural formula: |
![structural formula structural formula](t-pv201.gif) |
The analyte air concentrations throughout this method are based on
the recommended sampling and analytical parameters of 30 liters and a
desorption volume of one mL. Air concentrations listed in ppm are
referenced to 25ºC and 101.3 kPa (760 mmHg).
1.2 Limit defining parameters
1.2.1 Detection limit of the overall procedure (DLOP)
The detection limit of the overall procedure is 0.8 µg per sample
(0.008 ppm or 0.03 mg/m³). This is the amount of analyte spiked on the
sampler that will give a response that is significantly different from
the background response of a sampler blank.
The DLOP is defined as the concentration of analyte that gives a
response (YDLOP) that is significantly different (three
standard deviations (SDBR)) from the background response
(YBR).
YDLOP - YBR = 3(SDBR)
The direct measurement of YBR and SDBR in
chromatographic methods is typically inconvenient, and difficult
because YBR is usually extremely low. Estimates of these
parameters can be made with data obtained from the analysis of a
series of samples whose responses are in the vicinity of the
background response. The regression curve obtained for a plot of
instrument response versus concentration of analyte will usually be
linear. Assuming SDBR and the precision of data about the
curve are similar, the standard error of estimate (SEE) for the
regression curve can be substituted for SDBR in the above
equation. The following calculations derive a formula for the DLOP:
SEE |
= |
√ |
|
Σ(YOBS - YEST)2 |
|
n - k |
|
Yobs =
observed response Yest = estimated
response from regression curve n = total no.
of data points k = 2 for a linear regression
curve |
At point YDLOP on the regression curve
YDLOP = A(DLOP) + YBR ,
A = analytical sensitivity
(slope) | therefore
Substituting 3(SEE) + YBR for YDLOP gives
The DLOP is the amount of aniline spiked on the adsorbing section
of the acid coated XAD-7 tubes that will give a response that is
significantly different from the background response. Several tubes
were spiked with various amounts of aniline from approximately 0.4 to
6 µg. These were stored overnight at ambient temperature. The next day
these samples were desorbed and analyzed. The data obtained was used
to calculate the required parameters (A = 784 and SEE = 208) for the
calculation of the DLOP.
Table 1.2.1 Detection Limit of the Overall
Procedure
|
mass per sample (µg) |
area counts (µV-s) |
|
0 0.38 0.38 0.76 0.76 1.52 1.52 2.28 2.28 3.04 3.04 3.80 3.80 4.56 4.56 5.32 5.32 6.08 |
0 428 323 1119 699 1400 1222 1993 2121 2936 2459 3350 2660 3665 3717 4282 4462 4912 |
|
Figure 1.2.1 Plot of data to determine the DLOP/RQL
1.2.2 The reliable quantitation limit (RQL) is 2.7 µg per sample
(0.02 ppm or 0.09 mg/m³). This is the amount of analyte spiked on a
sampler that will give a signal that is considered the lower limit for
precise quantitative measurements.
The RQL is considered the lower limit for precise quantitative
measurements. It is determined from in the regression line data
obtained for the calculation of the DLOP (Section 1.2.1), providing at
least 75% of the analyte is recovered. The RQL is defined as the
concentration of analyte that gives a response (YRQL) such
that
YRQL - YBR = 10(SDBR)
therefore
![For problems with accessibility in using figures please contact the SLTC at (801) 233-4900. For problems with accessibility in using figures please contact the SLTC at (801) 233-4900.](t-pv203.gif) Figure 1.2.2 Reliable quantitation limit
chromatogram.
2. Sampling Procedure
2.1 Apparatus
2.1.1 Samples are collected using a personal sampling pump
calibrated, with the sampling device attached, to within ±5% of the
recommended flow rate.
2.1.2 Samples are collected on 10% phosphoric acid coated XAD-7
tubes, lot 540, containing 80 mg adsorbing section with 40 mg backup
section. The sections are separated by a 2 mm urethane foam plug, with
a silanized glass wool plug before the adsorbing section and a 3 mm
urethane foam plug at the back of the backup section. The ends of the
glass tube are flame sealed and the tube containing the adsorbent is 7
cm long with a 6 mm outside diameter. SKC tubes or equivalent tubes
may be used.
2.2 Technique
2.2.1 Immediately before sampling, break off the ends of the
sampling tube. All tubes should be from the same lot.
2.2.2 Attach the sampling tube to the sampling pump with flexible
tubing. It is desirable to utilize sampling tube holders which have a
protective cover to shield the employee from the sharp, jagged end of
the sampling tube. Position the tube so that sampled air passes
through the sampling, larger, section of the tube first.
2.2.3 Air being sampled should not pass through any hose or tubing
before entering the sampling tube.
2.2.4 Attach the sampler vertically with the sampling, larger,
section downward, in the worker's breathing zone, and positioned so it
does not impede work performance or safety.
2.2.5 After sampling for the appropriate time, remove the sample
and seal the tube with plastic end caps. Wrap each sample end-to-end
with a Form OSHA 21 seal.
2.2.6 Submit at least one blank sample with each set of samples.
Handle the blank sampler in the same manner as the other samples
except draw no air through it.
2.2.7 Record sample volumes (in liters of air) for each sample,
along with any potential interferences.
2.2.8 Ship bulk samples in separate containers from the air
samples.
2.3 Desorption efficiency
The desorption efficiencies (DE) of aniline were determined by
liquid-spiking the sampling tubes with aniline at 0.1 to 2 times the
PEL. These samples were stored overnight in a drawer at ambient
temperature. The next day the samples were desorbed and analyzed. The
average desorption efficiency over the studied range was
91.4%.
Table 2.3.1 Desorption Efficiency of Aniline at
0.1 × the PEL
|
sample |
µg spiked |
µg recovered |
recovery (decimal) |
|
1 2 3 4 5 6 |
57.03 57.03 57.03 57.03 57.03 57.03 |
53.77 53.29 51.85 53.89 51.08 54.23 |
0.943 0.934 0.909 0.945 0.896 0.951 |
|
Table 2.3.2 Desorption Efficiency of Aniline at
0.5 × the PEL
|
sample |
µg spiked |
µg recovered |
recovery (decimal) |
|
7 8 9 10 11 12 |
285 285 285 285 285 285 |
261 259 259 254 264 261 |
0.917 0.907 0.909 0.893 0.925 0.915 |
|
Table 2.3.3 Desorption Efficiency of Aniline at
1.0 × the PEL
|
sample |
µg spiked |
µg recovered |
recovery (decimal) |
|
13 14 15 16 17 18 |
570 570 570 570 570 570 |
520 511 518 494 501 545 |
0.912 0.895 0.908 0.867 0.879 0.956 |
|
Table 2.3.4 Desorption Efficiency of aniline at
2.0 × the PEL
|
sample |
µg spiked |
µg recovered |
recovery (decimal) |
|
19 20 21 22 23 24 |
1141 1141 1141 1141 1141 1141 |
1040 1042 1033 1051 1034 1040 |
0.912 0.913 0.906 0.922 0.906 0.912 |
|
2.4 Retention efficiency
Table 2.4.1 Retention Efficiency of Aniline at
2.0 × the PEL
|
sample |
µg spiked |
µg recovered |
recovery (decimal) |
|
R1 R2 R3 R4 R5 R6 |
1141 1141 1141 1141 1141 1141 |
1055 1045 1025 1047 1062 1047 |
0.925 0.916 0.899 0.918 0.931 0.918 |
|
The acid coated XAD-7 tubes were spiked with 1141 µg (10 ppm or 38
mg/m³) of aniline, allowed to equilibrate overnight in a drawer at
ambient temperature and then had 30 L humid air (80% RH at 25ºC) pulled
through them. They were opened, desorbed, and analyzed by GC-FID. The
retention efficiency averaged 92%. There was no aniline found on the
backup portions of the tubes.
2.5 Sample storage
The front sections of 12 acid coated XAD-7 sampling tubes were each
spiked with 570 µg (5 ppm) of aniline. They were sealed and stored
overnight at ambient temperature. The next day 30 L of humid air (80% RH
at 25ºC) was drawn through each tube at 0.2 L/min. Half of the tubes
were stored in a drawer at ambient temperature and the other half were
stored in a refrigerator at 0ºC. After 7 days of storage three samples
from the tubes stored under refrigeration and three samples from ambient
storage were analyzed. The remaining samples were analyzed after 14 days
of storage. The amounts recovered, which are not corrected for
desorption efficiency, indicate good storage stability for the time
period studied.
Table 2.5 Sample Storage
|
Ambient Storage |
Refrigerator Storage |
days |
µg theory |
µg found |
recovery (decimal) |
days |
µg theory |
µg found |
recovery (decimal) |
|
7 |
570 |
460 |
0.807 |
7 |
570 |
478 |
0.838 |
7 |
570 |
493 |
0.865 |
7 |
570 |
495 |
0.868 |
7 |
570 |
478 |
0.838 |
7 |
570 |
490 |
0.86 |
14 |
570 |
559 |
0.98 |
14 |
570 |
551 |
0.966 |
14 |
570 |
545 |
0.956 |
14 |
570 |
564 |
0.99 |
14 |
570 |
554 |
0.972 |
14 |
570 |
578 |
1.01 |
|
2.6 Recommended air volume and sampling rate.
2.6.1 The recommended air volume is 30 L.
2.6.2 The recommended sampling rate is 0.2 L/min.
2.7 Interferences
2.7.1 It is not known if any compounds will interfere with the
collection of aniline on 10% phosphoric acid coated XAD-7 tubes. In
general, the presence of other contaminant vapors in the air will
reduce the capacity of adsorbent tubes to collect aniline.
2.7.2 Any suspected interferences should be reported to the
laboratory.
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 being
sampled.
2.8.3 Wear eye protection when breaking the ends of the glass
sampling tubes.
3. Analytical Procedure
3.1 Apparatus
3.1.1 A gas chromatograph (GC) equipped with a flame ionization
detector (FID). A Hewlett Packard (HP) model 5890 was used in this
evaluation.
3.1.2 A GC column capable of separating the analyte and an internal
standard from any interferences. The column used in this study was a
60 m RTX-5, 1.0 µm film thickness, 0.32- mm i.d.
3.1.3 An electronic integrator or some suitable method of measuring
peak areas. A Waters 860 data system was used in this evaluation.
3.1.4 Two milliliter vials with Teflon-lined caps.
3.1.5 A 10 µL syringe or other convenient size for standard
preparation.
3.1.6 Pipettes for dispensing the desorbing solution. A dispenser
may be used.
3.1.7 Volumetric flasks - 5 mL and other convenient sizes for
preparing standards.
3.2 Reagents
3.2.1 Purified GC grade nitrogen, hydrogen, and air.
3.2.2 Aniline, Reagent grade
3.2.3 Methanol, reagent grade.
3.2.4 1-Hexanol, reagent grade. This was used as an internal
standard.
3.2.5 Ammonium hydroxide, reagent grade.
3.2.6 Desorbing solution. The desorbing solvent was prepared by
adding 1-hexanol and ammonium hydroxide to methanol at 25 µL/mL and
0.2N concentrations respectively.
3.3 Standard preparation
3.3.1 Stock standards are prepared by diluting a known quantity of
aniline with the desorbing solution.
3.3.2 Dilutions of the stock standards with desorbing solution were
made to obtain lower working range standards.
3.4 Sample preparation
3.4.1 Sample tubes are opened and the front and back section of
each tube are placed in separate 2 mL vials.
3.4.2 Each section is desorbed with 1 mL of the desorbing
solution.
3.4.3 The vials are sealed immediately and allowed to desorb for 30
minutes on a mechanical shaker.
3.5 Analysis
3.5.1 Gas chromatograph conditions.
Injection size: |
1 µL |
Flow rates (mL/min) |
|
Nitrogen (make-up): |
30 |
Hydrogen(carrier): |
1.5 |
Hydrogen(detector): |
60 |
Air: |
450 |
Temperatures (ºC) |
|
Injector: |
200 |
Detector: |
250 |
Oven: |
120 |
Retention times (min) |
|
ISTD |
6.9 |
Aniline |
10.9 |
N,N-Dimetnylaniline |
18.1 |
Figure 3.5.1 Chromatogram at the PEL
3.5.2 Peak areas are measured with a data system or other suitable
means.
3.6 Interferences (analytical)
3.6.1 Any compound that produces a response and has a similar
retention time as the analyte or internal standard is a potential
interference. If any potential interferences were reported, they
should be considered before samples are desorbed. Generally,
chromatographic conditions can be altered to separate an interference
from the analyte.
3.6.2 When necessary, the identity of an analyte peak may be
confirmed by GC-Mass spectrometry or by another analytical
procedure.
Figure 3.6.2 Mass Spectrum of Aniline (Ref. 5.8)
3.7 Calculations
3.7.1 Construct a calibration curve by plotting detector
response versus concentration (µg/mL) of aniline.
Figure 3.7.1
Calibration Curve
3.7.2 Determine the µg/mL of aniline in each section of the samples
and blank from the calibration curve.
3.7.3. Blank correct each sample by subtracting the µg/mL found in
each section of the blank from the µg/mL found in the corresponding
sections of the samples and then add the results together for the
total µg/mL for each sample.
3.7.4 Determine the air concentration using the following
formula.
mg/m3 |
= |
(μg/mL, blank corrected)(desorption volume, mL) |
|
(air volume, L)(desorption efficiency, decimal) |
where:
24.46 = molar volume (liters/mole) at 101.3 kPa (760 mmHg) and
25ºC
MW = molecular weight (g/mole) of aniline
3.8 Safety precautions
3.8.1 Adhere to the rules set down in your chemical hygiene plan
(which is mandated by the OSHA laboratory standard).
3.8.2 Avoid skin contact and inhalation of all chemicals.
3.8.3 Wear safety glasses, gloves and a lab coat at all times while
in the laboratory areas.
4. Recommendations for Further Study
Collection studies need to be performed from a dynamically generated
test atmosphere.
5. References
5.1 NIOSH Manual of Analytical Methods, 3rd. ed; Eller, P. M.,
Ed.; U.S. Department of Health and Human Services, Public Health
Service, Centers for Disease Control, National Institute for
Occupational Safety and Health, Division of Physical Sciences and
Engineering: Cincinnati, DHHS (NIOSH) Publication No. 84-100, 1984,
Method 2002.
5.2 Wood, Gerry and Anderson, Robert Am. Ind. Hyg. Assoc. J,
1975, 36(7), 538-548.
5.3 Kirk-Othmer Encyclopedia of Chemical Technology, 3rd ed.;
Grayson, M. Ed.; John Wiley & Sons: New York, 1980, Vol. 2; pp
309-316.
5.4 Documentation of the Treshold Limit Values and Biological
Exposure Indices, 5th. ed.; American Conference of Governmental
Industrial Hygienists, Inc.: Cincinnati, 1986; p 30.
5.5 IRAC Monographs on the Evaluation of Carcinogenic Risks of
Chemicals to Humans, Some Aromatic Amines, Anthraquinones and Nitroso
Compounds, and Inorganic Fluorides Used in Drinking-water and Dental
Preparations; Volume 27; International Agency for Research on
Cancer, Secretariat of the World Health Organization: UK, 1982, ISBN 92
8 321227 4.
5.6 IRAC Monographs on the Evaluation of Carcinogenic Risks to
Humans, Overall Evaluations of Carcinogenicity: An Updating of IRAC
Monographs Volumes 1 to 42, Supplement 7; International Agency for
Research on Cancer, Secretariat of the Wold Health Organization: UK,
1987, ISBN 92 832 1411 0, ISSN 0250-9555.
5.7 Registry of Toxic Effects of Chemical Substances 1985-86
Edition; DHHS(NIOSH) Publication No. 87-114, U.S. Department of
Health and Human Services: Cincinnati, OH, 1987; p 478.
5.8 EPA/NIH Mass Spectral Data Base, Vol. 1, 1980,p
58.
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