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These procedures were designed and tested for internal use by OSHA personnel. Mention of any company name or commercial product does not constitute endorsement by OSHA.
Related Information: Chemical Sampling -
1. General Discussion
||0.3 mg/m3 (0.10 ppm) (OSHA PEL)
||The sampling train consists of a 13-mm glass fiber
filter in a Swinnex cassette (available from the laboratory), followed
by a standard silica gel tube. The filter and gaskets, within the
cassette used to hold the filter, are extracted in the field in exactly
1 mL of methanol. This extraction is very important so a volumetric
pipette calibrated to 1 mL must be used. The silica gel tube is
extracted with methanol at the laboratory. Analysis is performed by
gas chromatography (GC) using a nitrogen/phosphorous detector.
|Recommended air volume and sampling rate:
120 L at 1 L/min
|Detection limit of the
Glass fiber filter 3.8 µg/m3 (1.3 ppb)
Silica gel 3.8 µg/m3 (1.3 ppb)
|Reliable quantitation limit:
||Glass fiber filter 3.8 µg/m3 (1.3 ppb)
Silica gel 3.8 µg/m3 (1.3 ppb)
|Standard error of estimate:
||As soon after sampling as possible, the glass fiber
filter and the gaskets holding the filter in place must be added to
1 mL of methanol. This is done to avoid sublimation of any acrylamide
particulate collected on the filter.
|Status of method:
||This method has been subjected to the established
evaluation procedures of the Organic Methods Evaluation Branch.
Michael L. Shulsky
Methods Development Team
Industrial Hygiene Chemistry Division
OSHA Salt Lake Technical Center
Sandy UT 84070-6406
2. Sampling Procedure
1.1.1. History of procedure
1.2. Limit defining parameters (All values are based on the recommended
There is little published data on the collection of acrylamide, but manufacturers have used a variety of methods
due to the possibility of acrylamide being present as a
vapor or aerosol. The sampling procedures used include
filters, midget impingers, and adsorbent tubes.
Various analytical techniques have been employed: spectrophotometry with derivatization, refractive index measurements, titrimetry, GC with derivatization, direct GC, thin layer chromatography, polarography (Ref. 5.1.), and
liquid chromatography (LC). (Ref. 5.2.)
A glass fiber filter backed up with a silica gel tube was
evaluated for this procedure. It was found that solid
acrylamide will vaporize from a filter rather rapidly when
air is drawn through it. The filter is recommended for
collection of particulate acrylamide since the collection
efficiency of sorbent tubes is not known. Silica gel
tubes were chosen to back up the filter because they provide good collection and resorption efficiencies. Poor
desorptions were obtained from charcoal with methanol-
water mixtures. Other solvents were evaluated for resorption of charcoal, but did little to increase the resorption efficiency.
Gas chromatographic analysis was selected. The variability of conditions and columns are sometimes needed to eliminate interferences. A nitrogen-phosphorus detector (NPD)
was chosen because of its selectivity and sensitivity.
The plastic cassettes which hold a 37-mm filter were unsuitable for the sampling train. The cassette appeared to
be responsible for low and erratic recoveries of acrylamide. This was determined by spiking a known amount of
acrylamide on a glass wool plug inside a glass tube (both
parts silanized), and placing the glass tube ahead of the
plastic cassette in the sampling train. One hundred twenty liters of humid air, at approximately 75% relative
humidity (RH), was drawn through the glass tube assembly
cassette, and silica gel tube. The sampling train, including the glass tube assembly and rinses from the cassette
were analyzed separately. Acrylamide was found only on
the "A" portion of the silica gel tube. The recovery from
numerous tests of this procedure ranged between 65% and
100% . In order to check the technique of spiking the
glass wool plug, bubblers of isopropanol were used instead
of a cassette and silica gel tube. These tests gave 95 to
100% recovery. Therefore, it was assumed the cassette was
introducing errors in recovery. Smaller Swinnex cassettes
were tried with the same spiking technique. The recovery
was 95 to 100%.
1.1.2. Toxicity (This section is for information only and should
not be taken as the basis for OSHA policy.)
Acrylamide may be absorbed through the skin or by inhalation. Workers exposed to the dust for 4 to 12 weeks showed symptoms of muscular weakness particularly in the legs,
numbness of the limbs, absence of deep tendon reflex,
fatigue, and lethargy. These problems were slow to disappear, in some cases taking months. (Ref. 5.3.)
Acrylamide is used primarily in the production of polymers. Polyacrylamide is used as flocculent in water and
waste treatment. The paper industry also uses polyacrylamide for strengtheners. There are approximately 20,000
workers potentially exposed to acrylamide. (Ref. 5.1.)
1.1.4. Physical properties (Ref. 5.4. unless otherwise stated)
||71.08 (Ref. 5.1.)
||125°C (25 mm Hg)
||0.007 mm Hg at 25°C
sublimes at room temperature (Ref. 5.1.)
||propenamide, acrylic amide,
akrylamide (Ref. 5.1.)
1.2.1. Analytical detection limit
The detection limit of the analytical procedure is 0.9 ng
per 2-µL injection. This is the amount of acrylamide
which gave a chromatographic peak 5 times the baseline
noise. (Section 4.1.1.)
1.2.2. Detection limit of the overall procedure
This detection limit is 0.45 µg for each component of the sampling
train (silica gel tube and glass fiber filter). The above amount, 0.45 µg,
spiked on each collection media, gave a recovery equal to the analytical detection
limit. (Section 4.2.)
1.2.3. Reliable quantitation limit
The reliable quantitation limit is 0.45 µg for each collection medium which is equivalent to 3.8 µg/m3 or 1.3
ppb . This is equal to the analytical detection limit
since recovery never fell below 75% and the 95% confidence
limit remained within ±25%.
The reliable quantitation limit and detection limits reported in
this method may be better or worse than another analyst may obtain. This is due to the factors which will effect sensitivity of
an NPD such as age of the bead, the voltage applied to the bead,
and the flow rate of the carrier gas and detector gases.
The sensitivity for the analytical procedure over the
concentration range of 0.4 to 2 times the PEL based on a
120-L air volume is 6160 area units per µg/mL. This value
is the slope of the calibration curve. (Section 4.3.) The
sensitivity will vary with the instrument and data system
The recovery of acrylamide from samples used in a 15-day
storage test remained above 89% for samples spiked with 40
µg of acrylamide. (Section 4.6.) The recovery of analyte
from the collection medium during storage must be 75% or
1.2.6. Precision (analytical method only)
The pooled coefficient of variation obtained from replicate injections of analytical standards at 0.5, 1.0, and 2
times the PEL is 0.0312. (Section 4.2.)
1.2.7. Precision (overall procedure)
The precision at the 95% confidence level for the 15-day
storage test is ±14.8%. (Figure 4.7.) This includes an
additional ±5% for sampling error. The overall procedure
must provide results that are ±25% at the 95% confidence
1.3.1. The sampling device is small and portable.
1.3.2. Replicate injections of each sample are possible.
1.3.3. Samples are stable for at least two weeks.
1.3.4. The analytical technique is sensitive and selective.
1.4.1. The precision of the sampling pump is dependent on the
pressure drop across the sampling train.
1.4.2. The filter portion and gaskets, which hold the filter, of
each sample must be extracted with methanol as soon after
sampling as possible. It may be advantageous to place
exactly 1 mL of methanol in enough scintillation vials to
accommodate the expected number of samples prior to going
to the sampling site. After sampling, the cassette could
be unscrewed and the filter and gaskets simply dropped
into a vial already containing exactly 1 mL of methanol.
1.4.3. Methanol is toxic and must be handled cautiously.
3. Analytical Procedure
2.1.1. A personal sampling pump which may be calibrated within
±5% of the recommended flow rate.
2.1.2. Silica gel tubes containing a 150-mg and a 75-mg portion.
The tubes used in the evaluation were obtained from SKC,
Inc., and were 6-mm i.d. × 70 mm in length.
2.1.3. Scintillation vials with Teflon-lined caps, i.e., 20-mL.
2.1.4. The Swinnex cassettes with filters and gaskets can be
obtained from the laboratory.
2.1.5. Tygon tubing is used to connect the cassette to the silica
gel tube. This tubing should be as short as possible.
2.1.6. A 1-mL pipette is necessary for dispensing methanol into
the scintillation vials.
Methanol, reagent grade.
2.3. Sampling technique
2.3.1. Before going to the workplace, exactly 1.0 mL of methanol
is placed in scintillation vials and capped tightly. There should be enough scintillation vials with 1 mL of
methanol, to extract each filter sample taken.
2.4. Sampler capacity
2.3.2. A short piece of Tygon tubing is used to connect the cassette to the silica gel tube, such that the silica gel
tube is butted against the cassette.
2.3.3. Immediately before sampling, the ends of the silica gel
tube are broken, the cassette and silica gel tube are
connected, and the tube is connected to a sampling pump
with a flexible hose.
2.3.4. The sampling device, cassette followed by a silica gel
tube, is placed vertically on the employee to avoid channeling through the tube.
2.3.5. Immediately after sampling, seal the ends of the silica
gel tubes with plastic caps and wrap it lengthwise with an
official OSHA seal (Form 21).
2.3.6. As soon as possible, unscrew the cassette and place, the
glass fiber filter and O-ring gaskets in a vial containing
1 mL of methanol. Be certain the cap is tightly screwed
on the vial, then wrap the vial lengthwise with an official OSHA seal.
2.3.7. With each set of silica gel tubes send in a blank.
2.3.8. Submit a blank sample of the methanol used for extraction,
containing a blank filter and gaskets.
2.3.9. If a bulk sample is submitted for analysis, it should be
sent in a glass bottle sealed with a Teflon-lined cap.
Bulk samples must not be shipped in the same package with
2.3.10. Transport the samples, Swinnex cassettes, and corresponding paperwork to the laboratory for analysis.
Since a controlled test atmosphere could not be produced, an exact
determination of breakthrough capacity could not be obtained easily.
Instead, the retention efficiency for a high concentratlon of
acrylamide spiked on the silica gel tube was determined.
A study was performed by spiking a filter with a large amount of
acrylamide, then attaching a silica gel tube behind it.
One hundred-eighty liters of humid air (approx. 75% RH, 20°C) was pulled
through the assembled sampling train. The "A" and "B" portions of
the silica gel tube were analyzed. The "A" portion contained
0.644 mg of acrylamide while the "B" portion contained none. This
amount (0.644 mg) is approximately 17 times the amount for a sample at the PEL.
2.5. Desorption and extraction efficiencies
2.5.1. Desorption efficiencies were determined by liquid injections of methanol/acrylamide solutions onto the "A"
portion of the silica gel tubes. Studies were done over
the range of 2 times the PEL down to the detection limit
of the analytical procedure assuming a 120-L air volume.
Six tubes were prepared at each loading. The average
resorption efficiency was 97.7%. (Section 4.5.)
2.6. Recommended air volume and sampling rate
2.5.2. Extraction efficiencies for the filters were done at 40 µg
and 0.9 µg of acrylamide. These were prepared by liquid
injection onto the filters and immediately extracted with
1 mL of methanol. These gave 100% recovery so there is no
correction necessary for the filter portion.
The recommended air volume is 120 L at a sampling rate not to
exceed 1 L/min.
2.7.1. Other organic vapors may collect on the silica gel tubes.
Any other organic vapors present should be listed as possible interferences.
2.8. Safety precautions
2.7.2. Other organic particulate or aerosols may collect on the
filter so they should be listed as possible interferences.
2.7.3. Large amounts of dust may plug the filter, so it should be
watched if a dusty environment is encountered.
2.8.1. Eye protection should be worn during the breaking of the
ends of the silica gel tubes.
2.8.2. Methanol is a flammable and toxic solvent, so it should be
handled with care.
4. Backup Data
3.1.1. Gas chromatography equipped with a nitrogen/phosphorus
3.1.2. Microliter syringes, such as 2-µL and 10-µL sizes.
3.1.3. Analytical GC column. For this evaluation a 3-ft glass
column, 2-mm i.d. × 1/4-in. o.d., containing 10% Carbowax
20M with 2% KOH on 80/100 Chromosorb W AW, was used.
3.1.4. Pipettes and dispensers for standard preparation and sample desorption.
3.1.5. Volumetric, such as 5-mL and 10-mL sizes.
3.1.6. Small vials for desorption of silica gel.
3.1.7. A suitable method for peak area integration.
3.2.1. Acrylamide, reagent grade.
3.3. Standard preparation
3.2.2. Methanol, GC quality.
3.2.3. Helium, hydrogen, air; GC quality.
Nitrogen/phosphorus detectors may not be linear over a wide range
of analyte concentration. The linearity must be ascertained before a quantitative method is chosen. Standards covering the
concentration range in which the samples are expected to be should
be prepared by weighing acrylamide into two volumetric, diluting
them to the mark with methanol, and making dilutions of these
stock standards down to the desired range. Analysis of the dilutions to be used with the samples will show whether the detector
is linear or not.
If the detector is linear over the desired range, then a direct
correlation between area of the acrylamide peak obtained from a
standard and concentration of that standard can be made.
If the detector response is not linear, then a suitable calibration curve must be used to correlate the area of a peak to the
3.4. Sample preparation
3.4.1. The 150-mg portion of silica gel and the glass wool plug
are placed in one vial while the 75-mg portion is placed
in a second vial. The urethane foam plugs are discarded.
3.5. Instrument conditions
3.4.2. Each portion of silica gel is desorbed with 1 mL of methanol, periodically shaken to insure all the silica gel has
been wetted, and analyzed, at least 20 min later.
3.4.3. The filters and gaskets are extracted by the field personnel as per Section 2.3.6.
||3-ft glass 2-mm i.d. × 1/4-in. i.d.
10% Carbowax 20M/2% KOH on 80/100
Chromosorb W AW
||nitrogen - 20 mL/min
||Hewlett-Packard Alkali Bead
||air - 50 mL/min
hydrogen - 3 mL/min
3.5.2. A typical chromatogram is shown in Figure 4.8.
3.6.1. Any compound which has the same retention time as
acrylamide and will respond on a NPD will be an interference.
By altering chromatographic conditions, the interfering
compound may be separated. It may be necessary to change
analytical columns. A second column to use is a 3-ft
glass column 1/4-in. o.d. × 2-mm i.d. packed with 10%
SP1000 on 80/100 Supelcoport.
3.6.2. If a sample is calculated to be above the PEL, then a
confirmation should be done by mass spectrometry or another suitable method. Retention time on one column is
not considered proof of identity. Two different types of
packing should be used to compare retention times.
If either calibration method, linear or non-linear is used as
described in Section 3.3., the values obtained for samples will
be in concentration units. For each sample there will be results
for the glass fiber filter and the silica gel tube.
Example: Air Volume = 110 L
Quantitation method gives the following results:
Both collection media are extracted with 1 mL of methanol. Therefore, the total µg from the filter is a simple multiplication: 2
µg/mL × 1 mL = 2 µg while the total micrograms for the silica gel
must take into account the desorption efficiency, 97.7%. The calculation is as follows:
Glass fiber filter = 2 µg/mL
Silica Gel = 20 µg/mL
The total µg for the sample is obtained by adding the results of
the GFF to the silica gel results.
| = 20.47 µg/mL × 1 mL = 20.47 µg
2 µg + 20.47 µg = 22.47 µg
The air concentration for the sample is calculated by dividing the
total pg for the sample by the air volume in L.
22.47 µg/110 L = 0.204 µg/L = 0.2 mg/m3
The result for the sample is 0.2 mg/m3.
3.8. Safety precautions
3.8.1. Safety glasses should be worn in all designated areas.
3.8.2. All solvents should be handled in an exhaust hood and kept
away from sources of ignition such as heated injectors and
4.1. Detection limit data
4.1.1. The detection limit of the analytical procedure is 0.9 ng
per 2-µL injection. This is the amount of acrylamide
which gave a chromatographic peak five times the baseline
noise. (Figure 4.1.)
4.2. Precision (analytical procedure)
4.1.2. The detection limit of the overall procedure is 0.45 µg
per collection medium (3.8 µg/m3 or 1.3 ppb). The above
amounts spiked on each collection medium gave a recovered
amount equal to the detection limit of the analytical
procedure. (Figure 4.2.)
4.1.3. The reliable quantitation limit is equal to 0.45 µg per
collection medium, since neither the desorption no; extraction fell below 75% and the 95% confidence limit remained within ±25%. (Figure 4.3.)
Based on the data of Table 4.2., the precision of the analytical
method at 0.5, 1, and 2 times the PEL, given as a pooled coefficient of variation, is 0.0312.
Precision of the Analytical Procedure
|× target conc.
CV = 0.0312
The sensitivity of this analytical procedure is defined as the
area change per µg/mL change as found from the slope of the calibration curve. (Figure 4.4.) For the instrument and data system
used, the sensitivity was 6160 area counts per µg/mL.
4.4. Sampler capacity
Breakthrough studies could not be done due to instrument limitations. Therefore, a retention study was performed by spiking a
glass fiber filter with a large amount of acrylamide, placing a
silica gel tube after the filter, and drawing 180 L of humid air
at 1 L/min through the sample train. Analysis of the "A" and "B"
portions of silica gel showed 0.644 mg (644 µg) of acrylamide on
the "A" portion and none on the "B" portion. The amount, 644 µg,
is approximately 20 times the amount collected for a sample at the
PEL with a 120-L air volume. This would give a wide safety margin
for most samples.
4.5. Desorption and extraction efficiencies
4.5.1. Desorption efficiencies were determined at 0.4, 1.1, and
2 times the PEL (Figure 4.5.), and at 0.45 µg and 2.25 µg.
(Figure 4.3.) Silica gel tubes were spiked by liquid
injection and stored in a refrigerator overnight. Upon
analysis an average desorption efficiency of 97.7% was
4.6. Storage test
|× target concentration
| = 97.7
4.5.2. Extraction efficiencies for filters were done by liquid
injection of acrylamide onto the filter and immediate
extraction with 1 mL of methanol. The amounts spiked were
0.9 µg and 40 µg. These gave 100% recovery, so no correction is necessary for the filter portion of the samples.
4.6.1. It was not possible to generate a controlled test atmosphere of acrylamide vapors and instrument limitations
prevented the generation of an aerosol of acrylamide, so
the stability samples were prepared by liquid injection
onto the "A" portion of silica gel tubes. Thirty-six
samples were prepared. Six of the samples were analyzed
after generation to be used for day zero results. Fifteen
samples were stored under refrigeration (5°C) and the
remaining 15 were stored at room temperature. On every
third day when possible, 3 samples from each storage set
were analyzed. The results are given below with graphic
representation in Figures 4.6. and 4.7.
4.6.2. The storage stability of filters was not done since acrylamide was
known to volatilize from the filters upon storage. Storage stability of
filters spiked with acrylamide then extracted with methanol was done on several filters.
This showed 100% recovery from the methanol solution after
a 17-day storage time.
Figure 4.1. Detection limit of analytical procedure.
Figure 4.2. Detection limit of overall procedure.
Figure 4.3. Reliable quantitation limit.
Figure 4.4. Sensitivity.
Figure 4.5. Desorption efficiencies.
Figure 4.6. Ambient storage of acrylamide.
Figure 4.7. Refrigerated storage of acrylamide.
Figure 4.8. Analytical standard (16 µg/mL).
5.1. "Occupational Exposure to Acrylamide." U.S. Department of Health, Education, and Welfare. 1976, No. 17-112.
5.2. Skelly, N.E.; Husser, E.R. Analytical Chemistry 1978, 14, 1959-1962.
5.3. Proctor, N.H., Hughes, J.P. "Chemical Hazards of the Workplace" J.B. Lippincott Company: Philadelphia, 1978, p. 88.
5.4. The Condensed Chemical Dictionary" 8th Ed.; Hawley, G.G., Ed.; Van Nostrand Reinhold Company, 1971; p. 100.