1. General Discussion
1.1 Background
1.1.1 History
Air samples collected on tubes containing XAD-2 resin coated with NITC were
received at SLTC along with a request for analysis for aminoethylethanolamine (AEEA).
This compound was collected on the same media used in OSHA Method 601, for
diethylene triamine, so those extraction and analytical parameters were used as
a starting point for AEEA. The AEEA was found to readily derivatize with the
NITC to form a stable derivative. The mobile phase of 80:20
isooctane:isopropanol gave a separation for the AEEA peak from interferences
from the NITC. The samples were extracted with dimethylformamide (DMF), with an
extraction efficiency mean of 99.7% for the concentration range of 20.7 to 413 µg/tube.
The retention efficiency study showed no AEEA on the back up section of the
spiked tube or back up tube, for tubes spiked with 413.2 µg
through which10-L humid air had been drawn. The storage study showed no loss for
samples stored for up to 14 days under both refrigerated and ambient conditions.
1.1.2 Toxic effects (This section is for information only and should
not be taken as the basis of OSHA policy.) 2,3
AEEA is a moderate skin irritant, severe eye irritant, and moderate mucous
membrane irritant. It is moderately toxic by ingestion, skin contact, and
inhalation. It can cause skin sensitization and chemical asthma.
1.1.3 Workplace exposure4,5
AEEA is used in textile finishing compounds such as antifuming agents,
dyestuffs, and cationic surfactants. It is used in resins, rubber products,
insecticides, and medical formulations. AEEA is listed in EPA’s HPV (high
production volume) list of chemicals produced and/or imported into the United
States.
1.1.4 Physical properties and other descriptive information6,7
CAS number:
|
111-41-1
|
IMIS:8
|
A120
|
molecular weight:
|
104.18
|
vapor density:
|
3.59
|
melting point:
|
<-18ºC
|
boiling point:
|
243.7ºC
|
appearance:
|
clear liquid
|
vapor
pressure:
|
0.0013 kPa @ 20ºC
|
odor:
|
mild ammoniacal
|
flash point:
|
135º C
(275ºF)(cc)
|
autoignition
|
|
density:
|
1.0304
|
temperature:
|
368ºC
(695ºF)
|
molecular formula:
|
C4H12N2O
|
solubility:
|
water, alcohol, acetone
|
synonyms:
|
N-(2-aminoethyl)ethanolamine;
2-[(2-aminoethyl)amino] ethanol;
N-hydroxyethyl-1,2-thanediamine; hydroxyethylethylenediamine;
monoethanolethylenediamine
|
structural formula:
|
|
This method was evaluated according to the OSHA SLTC "Evaluation
Guidelines for Air Sampling Methods Utilizing Chromatographic Analysis"9.
The Guidelines define analytical parameters, specify required laboratory
tests, statistical calculations and acceptance criteria. The analyte air
concentrations throughout this method are based on the recommended sampling
and analytical parameters.
1.2 Detection limit of the overall procedure (DLOP) and reliable
quantitation limit (RQL)
The DLOP is measured as mass per sample and expressed as equivalent air
concentrations, based on the recommended sampling parameters. Ten samplers
were spiked with equal descending increments of analyte, such that the highest
sampler loading was 10.34 µg
of AEEA. This is the amount spiked on a sampler that would produce a peak at
least 10 times the response for a sample blank. These spiked samplers were
analyzed with the recommended analytical parameters, and the data obtained
used to calculate the required parameters (standard error of estimate (SEE)
and slope) for the calculation of the DLOP. The slope was 2418 and the SEE was
1440. The RQL is considered the lower limit for precise quantitative
measurements. It is determined from the regression line parameters obtained
for the calculation of the DLOP, providing 75% to 125% of the analyte is
recovered. The DLOP and RQL were 1.79 µg
and 5.96 µg
respectively. The recovery at the RQL was 97.2%.
|
Table 1.2
Detection Limit of the Overall Procedure
for AEEA
|
mass per sample
(µg)
|
area counts
(µV·s)
|
|
0.00
1.03
2.07
3.10
4.14
5.17
6.20
7.24
8.27
9.31
10.34
|
0
1733
3890
5287
7345
9023
11528
15632
17639
22873
24876
|
|
Below is the chromatogram of the RQL level.
2. Sampling Procedure
All safety practices that apply to the work area being sampled should
be followed. The sampling equipment should be attached to the worker in
such a manner that it will not interfere with work performance or safety.
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 with 7-cm × 4-mm i.d. × 7-mm o.d.
glass sampling tubes packed with two sections (80/40 mg) of XAD-2
resin coated with 10% by weight 1-naphthylisothiocyanate. The
sections are held in place and separated with glass wool plugs.
For this evaluation, commercially prepared sampling tubes were
purchased from SKC, Inc. (catalog no. 226-30-18).
2.2 Reagents
None required.
2.3 Technique
2.3.1 Immediately before sampling, break off the ends of the
flame-sealed tube to provide an opening approximately half the
internal diameter of the tube. Wear eye protection when breaking
ends. Use tube holders to minimize the hazard of broken glass. All
tubes should be from the same lot.
2.3.2 The smaller section of the adsorbent tube is used as a
back-up and is positioned nearest the sampling pump. Attach the
tube holder to the sampling pump so that the adsorbent tube is in
an approximately vertical position with the inlet facing down
during sampling. Position the sampling pump, tube holder and
tubing so they do not impede work performance or safety.
2.3.3 Draw the air to be sampled directly into the inlet of the tube
holder. The air being sampled is not to be passed through any hose or
tubing before entering the sampling tube.
2.3.4 After sampling for the appropriate time, remove the
adsorbent tube and seal it with plastic end caps. Seal each sample
end-to-end with an OSHA-21 form as soon as possible.
2.3.5 Submit at least one blank sample with each set of
samples. Handle the blank sample in the same manner as the other
samples except draw no air through it.
2.3.6 Record sample air volumes (liters), sampling time
(minutes) and sampling rate (L/min) for each sample, along with
any potential interferences on the OSHA-91A form.
2.3.7 Submit the samples to the laboratory for analysis as soon
as possible after sampling. If delay is unavoidable, store the
samples at refrigerator temperature. Ship any bulk samples
separate from the air samples.
2.4 Extraction efficiency
The extraction efficiency was determined by spiking NITC-coated XAD-2
tubes with AEEA at 0.1 to 2 times the target concentration. These samples
were stored overnight at ambient temperature. Samples were extracted with
2-mL DMF, shaken for 30 minutes, and analyzed. The mean extraction
efficiency over the studied range was 99.7%. The wet extraction efficiency
was determined at 1 times the target concentration by spiking the analyte
onto NITC-coated XAD-2 tubes which had 10-L humid air (absolute humidity
of 15.9 mg/L of water, about 80% relative humidity at 22.2ºC)
drawn through them immediately before spiking. The mean recovery for the
wet samples was 98.7%.
Table 2.4
Extraction Efficiency (%) of AEEA
|
level |
sample number |
|
|
× target
concn |
µg per
sample |
1 |
2 |
3 |
4 |
5 |
6 |
mean |
|
0.1
0.25
0.5
1.0
1.5
2.0
1.0(wet) |
20.7
51.7
103
207
310
413
207 |
99.2
99.8
98.3
100.8
99.5
99.8
98.9 |
98.5
98.7
98.2
100.9
100.1
101.2
99.2 |
99.8
100.1
99.3
98.7
100.3
98.5
99.9 |
98.8
98.5
99.8
99.9
98.9
99.6
97.3 |
100.1
100.4
101.0
98.4
99.7
100.5
97.2 |
100.4
100.3
100.4
100.3
100.1
100.3
99.5 |
99.5
99.6
99.5
99.8
99.8
100.0
98.7 |
|
2.5 Retention efficiency
Six NITC-coated XAD-2 tubes were spiked with 413 µg
(9.7 ppm) of AEEA and allowed to equilibrate for 4 h. Each spiked tube was
placed in series with a second NITC-coated XAD-2 tube. Each sampling train
had 10-L humid air (absolute humidity of 15.9 mg/L of water, about 80%
relative humidity at 22.2ºC)
pulled through it at 0.1 L/min. The samples were extracted and analyzed. The
mean recovery was 99.4%. There was no analyte found on the backup section of
any of the spiked tubes or on the second tubes.
Table 2.5
Retention Efficiency (%) of AEEA
|
|
sample number |
|
section |
1 |
2 |
3 |
4 |
5 |
6 |
mean |
|
front of spiked tube
rear of spiked tube
front of series tube
back of series tube
total |
98.8
0.0
0.0
0.0
98.8 |
97.7
0.0
0.0
0.0
97.7 |
99.7
0.0
0.0
0.0
99.7 |
100.6
0.0
0.0
0.0
100.6 |
100.2
0.0
0.0
0.0
100.2 |
99.6
0.0
0.0
0.0
99.6 |
99.4
0.0
0.0
0.0
99.4 |
|
2.6 Sample storage
Fifteen NITC-coated XAD-2 tubes were each spiked with 207 µg
(4.86 ppm) of AEEA. They were allowed to equilibrate for 4 h, then 10-L of
air, with an absolute humidity of 15.7 milligrams of water per liter of air
(about 80% relative humidity at 23ºC),
was drawn through them. Three samples were analyzed immediately. The
remaining tubes were sealed and six were stored at room temperature (23ºC),
while the other six were stored at refrigerated temperature (4ºC).
Three of the samples stored at room temperature and three of the samples
stored at refrigerated temperature were analyzed after 7 days and the
remaining three of each group after 14 days. The results indicate good
storage stability for the time period studied.
Table 2.6
Storage Test for AEEA
|
time
(days) |
ambient storage
recovery (%) |
|
refrigerated storage
recovery (%) |
|
0
7
14 |
99.8
99.7
99.6 |
100.5
98.5
97.8 |
98.5
99.1
99.5 |
|
99.8
98.6
99.4 |
100.5
98.9
98.7 |
98.5
99.1
99.3 |
|
2.7 Recommended air volume and sampling rate.
Based on the data collected in this evaluation, 10-L air samples
should be collected at a sampling rate of 0.1 L/min for 100 minutes.
2.8 Interferences (sampling)
2.8.1 There are no known compounds which will severely interfere
with the collection of AEEA. Other primary and secondary amines will
collect on this medium, and form derivatives with the NITC,
affecting the ability of the tube to collect AEEA, so sampling time
should be adjusted if high concentrations of amines are expected.
2.8.2 Suspected interferences should be reported to the
laboratory with submitted samples.
3. Analytical Procedure
Adhere to the rules set down in your Chemical Hygiene Plan. Avoid
skin contact and inhalation of all chemicals and review all appropriate
MSDSs.
3.1 Apparatus
3.1.1 A liquid chromatograph equipped with a UV detector. For
this evaluation, a Waters 600 Controller and pump were used, with a
Waters 2487 Dual Wavelength Absorbance Detector, and a Waters 717
plus Autosampler was used.
3.1.2 An LC column capable of separating AEEA from the extraction
solvent and any potential interferences. A 4.6 × 250 mm column
packed with 5-µm
Bakerbond cyanopropyl (JT Baker, Phillipsburg, NJ) was used in the
evaluation.
3.1.3 An electronic integrator or some other suitable means of
measuring peak areas. A Waters Millennium32 Data System
was used in this evaluation.
3.1.4 Glass vials with poly(tetrafluoroethylene)-lined caps. For this
evaluation 4-mL vials were used.
3.1.5 A dispenser capable of delivering 2.0 mL of extracting
solvent to prepare standards and samples. If a dispenser is not
available, a 2.0-mL volumetric pipet may be used.
3.1.6 Volumetric flasks - 10-mL and other convenient sizes for
preparing standards.
3.2 Reagents
3.2.1 Aminoethylethanolamine (AEEA), reagent grade. Acros 99%
(lot 08515DS labeled 2-(2-aminoethyamine)ethanol) was used in this
evaluation.
3.2.2 N,N-Dimethyl formamide (DMF), reagent grade.
Fisher 99.5%+ (lot 933764) was used for this evaluation.
3.2.3 Isopropyl alcohol, HPLC grade. Fisher 99.9% (lot 0011554)
was used in this evaluation.
3.2.4 Isooctane, HPLC grade. Fisher 99.0%+ (lot 024943) was
used in this evaluation.
3.2.5 1-Naphthylisothiocyanate (NITC), reagent grade. Aldrich
95%+ (lot 09925MY) was used in this evaluation.
3.2.6 Mobile phase was 80:20 isooctane:isopropyl alcohol.
3.3 Standard preparation
3.3.1 Freshly prepare two stock standards. A stock standard of
2 mg/mL may be prepared by a) weighing out about 50 mg of NITC in
a 10-mL flask, b) weigh out 20 mg AEEA by placing the drops on top
of the NITC in the flask, and c) weigh out about 50 mg more NITC
on top of the AEEA, making sure that the AEEA is covered on all
sides by the NITC. Allow the AEEA to react with the NITC for at
least 1 hour before adding the DMF. Partially fill the volumetric
flask with DMF and allow to sit 30 minutes to begin dissolving the
derivative, then swirl the contents until all of the solids are
dissolved, and fill to the mark with DMF. Do not place the flask
in a sonic bath to try to get the derivative to go into solution,
as it will destroy the derivative. There must always be an excess
of the NITC for the derivative to be completely formed. There are
two amine groups which will react with the NITC, so this mole
ratio must be used in calculating the amount of NITC to be added.
For example, the amount of NITC needed for the above stock
standard would be calculated:
20 mg AEEA × (NITC MW=185.25/AEEA MW=104.15) ×2 = 71 mg
In the above stock standard preparation a total of 100 mg NITC
was weighed out so that an excess of NITC was present.
3.3.2 Diluted standards are prepared with a solution of 1 mg/mL
NITC in DMF, so that an excess of NITC is always present. Bracket
sample concentrations with working standard concentrations. If
sample concentrations are higher than the concentration range of
prepared standards, either analyze higher standards, or dilute the
sample. The higher standards should be at least as high in
concentration as the highest sample. Diluted samples should be
prepared with a solution of 1 mg/mL NITC in the DMF. The range of
standards used in this study was from 0.5 to 250 µg/mL.
The instrument is calibrated on the amount of AEEA in each
standard.
3.4 Sample preparation
3.4.1 Remove the plastic end caps from the sample tubes and
carefully transfer the adsorbent sections to separate 4-mL vials.
Discard the glass tube and glass wool plugs.
3.4.2 Add 2.0 mL of DMF to each vial.
3.4.3 Immediately seal the vials with poly(tetrafluoroethylene)-lined
caps.
3.4.4 Agitate the vials on a shaker, or a rotator, for 30 minutes.
3.5 Analysis
3.5.1 HPLC conditions
column:
|
Bakerbond cyanopropyl (CN) column 4.6
× 250 mm
|
injection size: |
10 µL
|
mobile phase: |
1 mL/min 80:20
isooctane:isopropyl alcohol
|
detector: |
UV at 254 and 280 nm
|
run time: |
14 min
|
retention times: |
1.7 min NITC
2.2 min DMF
6.8 min AEEA
|
|
|
3.5.2 Peak areas are measured by an integrator or other
suitable means.
3.5.3 An external standard (ESTD) calibration method is used. A calibration
curve can be constructed by plotting response of standard injections versus
micrograms of analyte per sample. Bracket the samples with freshly prepared
analytical standards over a range of concentrations.
3.6 Interferences (analytical)
3.6.1 Any compound that produces a LC response
and has a similar retention time as the analyte is
a potential interference. If any potential
interferences were reported, they should be
considered before samples are extracted.
Generally, chromatographic conditions can be
altered to separate an interference from the
analyte.
3.6.2 When necessary, the identity or purity of
an analyte peak may be confirmed by a photodiode
array scan of the peak, by wavelength ratioing, or
by LC/mass spec.
3.7 Calculations
The amount of analyte per sampler is obtained from the
appropriate calibration curve in terms of micrograms per
sample, uncorrected for extraction efficiency. This total
amount is then corrected by subtracting the total amount
(if any) found on the blank. The air concentration is
calculated using the following formulas.
|
where:
|
CM
is concentration by weight (mg/m³)
M is micrograms per sample
V is liters of air sampled
EE is extraction
efficiency, in decimal form
|
|
where: |
CV
is concentration by volume (ppm)
VM is molar volume at 25ºC
and 760 mm = 24.46
CM is concentration by
weight
Mr is molecular weight =
104.18 |
4. Recommendations for further study
Collection, reproducibility, and other detection limit studies need to be
performed to make this a validated method.
1OSHA Sampling and Analytical Methods. http://www.osha.gov/dts/sltc/methods/index.html
(accessed 5/21/2002).
2Lewis, R., Sax’s Dangerous Properties of Industrial Materials, Van
Nostrand Reinhold: New York, 2002, p 176.
3Pepys, J., Asthma due to Inhaled Chemical Fumes: Amino-ethyl ethanolamine in
Aluminum Soldering Flux, Clin Allergy, 1972, 2(2), 197-204.
4Lewis, R., Ed, Hawley’s Condensed Chemical Dictionary, John Wiley &
Sons: New York, 2001, p 592.
5HPV Chemical List History. http://www.epa.gov/opptintr/chemrtk/opptsrch.htm
(accessed 5/21/2002).
6Lewis, R., Sax’s Dangerous Properties of Industrial Materials, Van
Nostrand Reinhold: New York, 2002, p 176.
7Cheminfo http://ccohs.ca/products/databases/cheminfo.html
(accessed 5/21/2002).
8OSHA Chemical Sampling Information http://www.osha.gov/dts/chemicalsampling/toc/toc_chemsamp.html (accessed 5/21/2002).
9Burright, D.; Chan, Y.; Eide, M.; Elskamp, C.; Hendricks, W.; Rose, M. C. Evaluation
Guidelines for Air Sampling Methods Utilizing Chromatographic Analysis; OSHA
Salt Lake Technical Center, U.S. Department of Labor: Salt Lake City, UT, 1999.
|