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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.
|Target concentration:||0.3 mg/m3 (0.10 ppm) (OSHA PEL)|
|Procedure:||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 overall procedure:||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:||7.06%|
|Special requirements:||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.|
Date: October 1980
Chemist: Michael L. Shulsky
Methods Development Team
Industrial Hygiene Chemistry Division
OSHA Salt Lake Technical Center
Sandy UT 84070-6406
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%.
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.)
|molecular weight:||71.08 (Ref. 5.1.)|
|boiling point:||125°C (25 mm Hg)|
|specific gravity:||1.122 (3°C)|
|vapor pressure:||0.007 mm Hg at 25°C
sublimes at room temperature (Ref. 5.1.)
|synonyms:||propenamide, acrylic amide,
akrylamide (Ref. 5.1.)
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 5 times the baseline noise. (Section 4.1.1.)
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.)
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 used.
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 greater.
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.)
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 level.
Methanol, reagent grade.
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 concentration 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.
The recommended air volume is 120 L at a sampling rate not to exceed 1 L/min.
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 concentration.
|column:||3-ft glass 2-mm i.d. x 1/4-in. i.d.
10% Carbowax 20M/2% KOH on 80/100
Chromosorb W AW
|carrier gas:||nitrogen - 20 mL/min|
|detector type:||Hewlett-Packard Alkali Bead
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:
Glass fiber filter = 2 µg/mL
Silica Gel = 20 µg/mL
Both collection media are extracted with 1 mL of methanol. Therefore, the total µg from the filter is a simple multiplication: 2 µg/mL x 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:
= 20.47 µg/mL x 1 mL = 20.47 µg
The total µg for the sample is obtained by adding the results of the GFF to the silica gel results.
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.
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
|x 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.
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.
|x target concentration
X = 97.7
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