1. General Discussion
||1.0 mg/m3 ACGIH TLV-TWA (dust)
||5.0 ppm ACGIH TLV-TWA (vapor)
||Samples are collected by drawing a known volume of
air through OSHA versatile sampler (OVS-7) tubes, containing a
glass fiber filter and two sections of XAD-7 adsorbent. Samples
are extracted with methanol and analyzed by high performance liquid
chromatography (HPLC) using an ultraviolet (UV) detector.
|Air volume and sampling rate:
||100 L and 1.0 L/min
|Detection limit of the overall procedure (based on
the recommended air volume):
|Status of method:
||Partially Validated. This method has been only partially evaluated and is presented for information and trial use.
|Date: January 1988 (final)
||Chemist: John M. Linkletter
|Carcinogen and Pesticide Branch
OSHA Analytical Laboratory
Sandy, Utah 84070
2. Sampling procedure
1.1.1. History of procedure
1.2. Limit defining parameters
This evaluation was undertaken to determine the effectiveness of the
OVS-7 sampling tube as a sampling device for caprolactam. It follows
the procedure developed for carbaryl. (Ref. 5.1)
1.1.2. Toxic Effects (This section is for information purposes and
should not be taken as the basis for OSHA policy.)
The acute oral LD50 for rats is 2140 mg/kg. The inhalation
TC Lo for humans is 100 ppm.
Caprolactam (dust) has been given a TLV-TWA of 1.0 mg/m3 and
caprolactam (vapor) has been given a TLV-TWA of 5.0 ppm by the ACGIH.
1.1.3. Potential workplace exposure
No estimate of workplace exposure was found. Caprolactam is used in
the manufacture of synthetic fibers, plastics, bristles, film,
coatings, synthetic leather, plasticizers, and paint vehicles;
cross-linking agent for polyurethanes; synthesis of amino acid
lysine. (Ref. 5.3)
1.1.4. Physical Properties: (Refs. 5.2 - 5.3
||soluble in water, chlorinated solvents, cyclohexene.
||3 mm Hg (100 °C) 50 mm Hg (180 °C)
1.2.1. The detection limit of the analytical procedure is 3.4 ng
per injection. This is the smallest amount of analyte which will
produce a peak 5 times the baseline noise.
3. Analytical procedure
2.1.1. Samples are collected by using a personal sampling pump that
can be calibrated to within ± 5% of the recommended flow rate with
the sampling device in line.
2.1.2. Samples are collected with OVS-7 tubes, which are specially
made 13 mm o.d. glass tubes that are tapered to 6 mm o.d. These tubes
are packed with a 140-mg, backup section and a 270-mg sampling section
of cleaned XAD-7. The backup section is retained by two foam plugs and
the sampling section is between one foam plug and a 13 mm diameter
glass fiber filter. The glass fiber filter is held next to the sampling
section by a polytetrafluoroethylene (PTFE) retainer. (See Figure 1)
No sampling reagents are required.
2.3. Sampling technique
2.3.1. Attach the small end of the OVS-7 sampling tube to the sampling
pump with flexible, plastic tubing such that the large, front section
of the sampling tube is exposed directly to the atmosphere. Do not
place any tubing in front of the sampler. The sampler should be
attached vertically (large end down) in the worker's breathing
zone in such a manner that it does not impede work performance.
2.4. Extraction Efficiency
2.3.2. After sampling for the appropriate time, remove the sampling
device and seal the tube with plastic end caps.
2.3.3. Wrap each sample end-to-end with an OSHA seal (Form 21).
2.3.4. With each set of samples, submit at least one blank. The
blank should be handled the same as the other samples except that
no air is drawn through it.
2.3.5. Bulks samples should be submitted for analysis in a separate
container. Do not ship with the air samples.
Five 13 mm glass fiber filters were each liquid spiked with 127.6
ug of caprolactam. The five filters, along with a blank filter,
were each placed in separate 4-mL vials which also contained 270
mg of XAD-7 adsorbent. These vials were stored overnight at room
temperature, and then extracted with 4 mL of methanol.
The average extraction efficiency for these five filters (with the
XAD-7 adsorbent present) was 111%.
2.5. Retention efficiency
Three OVS-7 tubes were each spiked with either 134.8 ug or 127.6
ug caprolactam by liquid spiking the 13 mm glass fiber filter.
One hundred liters of humid air (>70% RH) were drawn through each
tube. The three tubes were then extracted as in Section (3.4.).
No significant breakthrough to the backup section was observed.
The average retention efficiency for these two filters was 88.3%.
2.6. Three OVS-7 tubes were spiked with varying amounts of caprolactam
as above. One hundred liters of humid air (>70% RH) were drawn
through each tube. The tubes were stored for seven days at
ambient temperature in a drawer. These were extracted as in
Section (3.4.). No caprolactam was recovered from the backup
section of these tubes.
The average recovery after seven days of storage was 97.5%.
2.7. Recommended air volume and sampling rate
2.7.1. The recommended air volume is 100 L.
2.7.2. The recommended flow rate is 1.0 L/min.
It is not known if any compounds will interfere with the
collection of caprolactam. Suspected interferences should be
reported to the laboratory with submitted samples.
2.9. Safety precautions
2.9.1. Attach sampling equipment in such a manner that it will
not interfere with work performance or safety.
2.9.2. Follow all safety practices that apply to the work area
4. Recommendations for Further Study
3.1.1. A high-performance liquid chromatograph equipped with a
UV detector, and manual or automatic injector. A Waters M6000A pump,
Waters 710B autosampler, and Waters 490 UV variable wavelength
detector was used in this evaluation.
3.1.2. An HPLC column capable of separating caprolactam from any
interferences. A 25cm × 4.6 mm i.d. LC-18DB (5 micron)
Supelco column was used in this evaluation.
3.1.3. An electronic integrator or other suitable means of
measuring detector response. A Hewlett-Packard 3357 data system
was used in this evaluation.
3.1.4. Vials, 4-mL glass with PTFE-lined septa.
3.1.5. Volumetric flasks, pipets, and syringes for preparing
standards, making dilutions, and performing injections.
3.2.1. HPLC grade methanol.
3.3. Standard preparation
3.2.2. HPLC grade water. A Millipore Milli-Q system was used to
prepare the water for this evaluation.
3.2.3. Caprolactam, reagent grade.
Stock standard solutions are prepared by adding methanol to
pre-weighed amounts of caprolactam. Working range standard solutions
are prepared by diluting stock solutions with methanol. Stock and
dilute standards are stored in a freezer.
3.4. Sample preparation
3.4.1. Transfer each section, the 13-mm glass fiber filter, the
270-mg section and the 140-mg section, into separate vials. Use
a small glass funnel to facilitate the transfer of the adsorbent.
Discard the first and rear foam plug. Do not discard the glass
sampling tube; it can be reused after it has been cleaned with
surfactant or suitable solvent.
3.4.2. Add 4.0 mL of methanol to each of the three vials.
3.4.3. Seal the vials with PTFE-lined septa and allow them to
extract for one hour. Shake the vials by hand periodically during
the one hour extraction time.
3.5.1. Instrument conditions
3.6. Interferences (analytical)
||25 cm × 4.6 mm i.d. stainless steel column,
packed with 5 um LC-DB18
||25% Methanol/75% water (v/v)
3.5.2. Chromatogram (See Figure 2)
3.6.1. Any collected compound that has the same retention time
as caprolactam and absorbs at 210 and 218 nm is an
interference. Generally, chromatographic conditions can
be altered to separate an interference from the analyte.
3.6.2. Retention time on a single column is not proof of chemical
identity. Analysis by an alternate HPLC column, detection at another
wavelength, comparison of absorbance response ratios, and confirmation
by mass spectrometry are additional means of identification.
3.7.1. A calibration curve is constructed by plotting detector
response versus standard concentration.
3.8. Safety precautions
3.7.2. The concentration of caprolactam in a sample is determined
from the calibration curve. If caprolactam is found on the backup
section, it is added to the amount found on the front section.
Blank corrections for each section should be performed before
adding the results together.
3.7.3. The air concentration is then determined by the following formula.
||(µg/mL in sample) × (extraction volume, mL)
(air volume, L) × (extraction efficiency, decimal)
3.8.1. Avoid exposure to all standards.
3.8.2. Avoid exposure to all solvents.
3.8.3. Wear safety glasses at all times.
This method should be fully validated.
Figure 1. OVS-7 Sampling Device
Figure 2. Chromatogram of Caprolactam
5.1. Burright, D., Method #63, "Carbaryl (Sevin)",
OSHA Analytical Laboratory, unpublished, 1987.
5.2. "Registry of Toxic Effects of Chemical Substances", 1983-4,
Cumulative Supplement to the 1981-2 Edition; U.S. Department of
Health Services, National Institute for Occupational Safety and
Health: 1985; volume 1; DHHS (NIOSH) Publ. (U>S>)
No. 86-103, p. 356.
5.3. "The Condensed Chemical Dictionary", Tenth ed., Van Nostrand
Reinhold Co., p.191., 1983.