1. General Discussion
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-2 tube
as a sampling device for coumaphos. It follows the procedure developed for
several other organophosphorus pesticides. (Ref. 5.1)
1.1.2 Toxic effects (This section is for information only and should not
be taken as the basis of OSHA policy).
The following paragraph is excerpted from the book OCCUPATIONAL DISEASES, A
Guide To Their Recognition. (Ref. 5.2)
The organic phosphorus compounds act as irreversible inhibitors of cholinesterase, thereby
allowing the accumulation of large amounts of
acetylcholine. When a critical level of cholinesterase depletion is reached, usually about
20% of normal, symptoms and signs of acetylcholine accumulation poisoning become manifest. Symptoms may include blurred vision,
weakness, nausea, headache, abdominal cramps,
chest discomfort, and diarrhea. Signs may
include miosis, muscle twitching, salivation,
sweating, tearing, cyanosis, convulsions, and
Besides being absorbed following inhalation or ingestion, organophosphorus pesticides are readily absorbed through
the intact skin (Ref. 5.2). When a particular pesticide
has a low dermal LD50, a skin notation,should be added to
the TLV or PEL.
Coumaphos has an acute oral LD50 of 13 mg/kg for rats.
Its acute dermal LD50 is 850 mg/kg for rats (Ref. 5.3).
Due to these factors an arbitrary target concentration
of 0.2 mg/m3, without a skin notation, was chosen for
1.1.3 Potential workplace exposure
No estimate of worker exposure to
coumaphos could be found. Coumaphos is used as an insecticide and nematocide.
|Physical properties (Ref. 5.4-5.6)
||0.000013 Pa (0.0000001 mm Hg) at
||1.5 ppm in water
soluble in aromatic solvents
somewhat soluble in alchohols and ketones
||Asuntol, Bay 21/199, Baymix, Co-Ral,
Diolice, Meldane, Muscatox, Resistox, Umbethion
The detection limit of the analytical procedure is 0.035 ng per injection.
This is the amount of analyte which will give a peak whose height is
approximately five times the baseline noise. This detection limit takes into
account the split ratio of 13.4 to 1 used on the capillary GC.
3. Analytical Procedure
2.1.1 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 OVS-2 tubes, which are specially made 13-mm o.d. glass tubes that
are tapered to 6-mm o.d. They are packed with a 140-mg backup section and a
270-mg sampling section of cleaned XAD-2. 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 polytetafluoroethylene (PTFE) retainer (See Figure 1)
No sampling reagents are required.
2.3 Sampling technique
2.3.1 Attach the small end of the OVS-2 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
2.4 Desorption efficiency
2.3.2 Attach the sampler vertically (large end down) in the worker's
breathing zone in such a manner that it does not impede work performance.
2.3.3 After sampling for the appropriate time, remove the sampling device
and seal the tube with plastic end caps.
2.3.4 Wrap each sample end-to-end with an OSHA seal (Form 21).
2.3.5 Submit at least one blank with each set of samples. Handle the blank
the same as the other samples, but do not draw air through it.
2.3.6 Submit any bulk samples in a separate container. Do not ship them
with the air samples.
A glass fiber filter and an amount of XAD-2 adsorbent equal to the sampling
section (270 mg) of an OVS-2 tube were placed in each of six 4-mL vials. These
vials were then sealed with
Five of these vials were then each liquid spiked with 22 µL of a 4.46 mg/mL
solution of coumaphos in toluene by injecting through the septum onto the glass
fiber filter. After replacing the punctured septa, these vials were allowed to
equilibrate overnight in a drawer at room temperature. They were then desorbed
with 2.0 mL of toluene containing triphenyl phosphate (TPP) as an internal
standard and analyzed as in Section 3.5.
|Average recovery is
2.5 Retention efficiency
Six OVS-2 tubes were each liquid spiked
with 22 µL of a 4.46
mg/mL solution of coumaphos in toluene by spiking the glass fiber
filter. These tubes were then sealed with plastic end caps and
stored in a drawer at room temperature. After overnight storage,
480 liters of humid air (approximately 70% relative humidity)
were drawn through each tube. Three of these tubes, along with a
blank tube, were then desorbed and analyzed as in Section 3. No
coumaphos was found on the backup sections of these tubes.
Retention Efficiency Study
|Average recovery is 98.8%
2.6. Sample storage
The remaining three spiked tubes from Section 2.5 (and a blank tube) were
stored for a total of 8 days in a drawer at room temperature. They were then desorbed and analyzed as in Section 3.
No coumaphos was found in the backup sections of these tubes.
|Average recovery is 97.1%
2.7 Recommended air volume and sampling rate
2.7.1 The recommended air volume is 480 L.
2.8 Interferences (sampling)
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 coumaphos. Suspected interferences should be reported to
the laboratory with submitted samples.
2.9 Safety precautions (sampling)
2.9.1 Attach the sampling equipment in such a manner that it
will not interfere with work performance or employee
2.9.2 Follow all safety practices that apply to the work area
4. Recommendations for Further Study
3.1.1 A GC equipped with an FPD. A Hewlett-Packard 5890A GC
(capillary) equipped with both an FPD operating in the
phosphorus mode and a Hewlett-Packard 7673A automatic
sampler was used in this evaluation.
3.1.2 A GC column capable of separating coumaphos from any interferences. A 45 m x 0.2 mm i.d. SE-54 capillary column, 0.25
µm thick film, was used in this evaluation and
is available from Supelco, Inc., Bellefonte, PA.
3.1.3 An electronic integrator or other suitable means of measuring detector response. A Hewlett-Packard 3392A Integrator and a Hewlett-Packard 3357 data system were used
in this evaluation.
3.1.4 Vials, 4-mL and 2-mL glass with PTFE-lined septa.
3.1.5 Volumetric flasks, pipets, and syringes.
3.2.1 Hydrogen, air, and nitrogen, GC grade.
3.3 Standard preparation
3.2.2 Toluene, Pesticide grade.
3.2.3 Coumaphos. A 98+% pure standard from EPA was used in
3.2.4 Triphenyl phosphate (TPP), practical grade from J.T.
Baker. If an internal standard method is used, the
desorbing solution is prepared by adding the internal
standard to the toluene. A 40 µg/mL solution of TPP was
used as the internal standard in this evaluation.
Prepare stock standards by adding either toluene or desorbing
solution (if an internal standard is used) to preweighed amounts
of coumaphos. Prepare working range standards by diluting stock solutions with
either toluene or desorbing solution (if an internal standard is used). Store stock and dilute standards in a
3.4 Sample preparation
3.4.1 Transfer the 13-mm glass fiber filter and the 270-mg
sampling section of the tube to a 4-mL vial. Place the
first foam plug and the 140-mg backup section in a
separate vial. A small glass funnel can be used to
facilitate the transfer of the adsorbent. Discard the
rear foam plug. Do not discard the glass sampling tube,
it can be reused.
3.4.2 Add 2.0 mL of either toluene or desorbing solution (if an
internal standard is used) to each vial.
3.4.3 Seal the vials with PTFE-lined septa and allow them to
desorb for one hour. Shake the vials by hand periodically during this time.
3.4.4 If necessary, transfer aliquots of the samples to the
vials used in GC analysis. In this evaluation, the samples were transferred to 2-mL glass vials, sealed with
PTFE-lined septa and loaded on the automatic sampler.
3.5.1 Analytical conditions (These conditions were developed
for a series of organophosphorus pesticides, which was run in several groups.
See Figure 2 for the group containing coumaphos.)
3.6 Interferences (analytical)
||45 m x 0.2 mm i.d. SE-54, 0.25 µm
||2.05 mL/min at 220°C
||13.4 to 1 at 220°C
|Oven temperature program
|Hydrogen flow rate:
|Air flow rate:
3.5.2 Chromatogram (See Figure 2)
3.6.1 Any compound having a retention time similar to that of
the analyte is a potential interference. Generally,
chromatographic conditions can be altered to separate
interferences from the analyte.
3.6.2 Retention time on a single column is not proof of chemical identity.
Analysis by an alternate GC column, detection by an FPD in the sulfur mode, detection by an
electron capture detector (ECD) and confirmation by mass
spectrometry are additional means of identification.
3.7.1 Construct a calibration curve by plotting detector response versus standard concentration.
3.8 Safety precautions (analytical)
3.7.2 Determine the concentration of coumaphos in each sample
from the calibration curve. If coumaphos is found on the
backup section, make blank corrections for each section
separately before adding the results together.
3.7.3 Determine the air concentration by the following formula.
||(µg/mL in sample)x(desorption volume, mL)
||(air volume, L)x(desorption efficiency, decimal)
3.8.1 Avoid exposure to all standards.
3.8.2 Avoid exposure to all solvents.
3.8.3 Year safety glasses at all times.
This method should be fully validated.
Figure 1. OVS-2 Sampling Device
Figure 2. Chromatogram of Coumaphos
This chromatogram also contains TPP and other pesticides
5.1 Burright, D.; Method #62, "Chlorpyrifos, DDVP, Diazinon, Malathion,
and Parathion"; OSHA Analytical Laboratory, unpublished, 1986.
5.2 "OCCUPATIONAL DISEASES, A Guide to their Recognition"; U.S. Department
of Health, Education, and Welfare; Public Health Service, Public Health Service
Publication No. 1097, U.S. Government Printing Office: Washington, D.C., 1964; p
5.3 "Registry of Toxic Effects of CHemical Substances", 1985-86 ed.; U.S.
Department of Health and Human Services (DHHS), Public Health Service, Centers
for Disease Control, National Institute for Occupational Safety and Health (NIOSH),
DHHS (NIOSH) Publication No. 87-114, U.S. Government Printing Office;
Washington, D.C., 1988; Vol. 2, pp 1679-80.
5.4 Windholz, M., Ed.; "Merch Index", 10th ed.; Merck and Co.: Rahway, NJ,
1983; p 366.
5.5 Ouellette, R.P. and King, J.A., Eds.; "Chemical Week Pesticides
Register"; McGraw-Hill Book Co.; New York, NY, 1977; p 167.
5.6 "Farm Chemicals Handbook"; Meister Publishing Co.: Willoughby, OH,
1985; pp C64-C65.