|| 0.25 mg/m3 Skin (ACGIH TLV-TWA)
|| Samples are collected by drawing known volumes of air through OSHA versatile sampler (OVS-2) tubes, each containing a glass fiber filter and two sections of
XAD-2 adsorbent. Samples are desorbed with toluene and analyzed by gas chromatography (GC) using a flame photometric detector
|Recommended air volume and sampling rate:
|| 480 L at 1.0 L/min
|Detection limit of the overall procedure based on
the recommended air volume:
|| 0.0073 mg/m3
|Status of method:
|| Stopgap method. This method has been partially evaluated and
is presented for information and trial use only
||David B. Armitage
1. General Discussion
Carcinogen and Pesticide Branch
OSHA Analytical Laboratory
1.1.1 History of procedure
This evaluation was undertaken to determine the effectiveness of the OVS-2 tube as a sampling device for dicrotophos. It follows the procedure developed for several other organophosphorus pesticides. (Ref.
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 coma.
2. Sampling Procedure
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.
1.2 Limit defining
Dicrotophos has an acute oral LD50 of 16 to 21 mg/kg for rats and an acute dermal LD50 of 42 to 43 mg/kg for rats. (Ref. 5.3)
Due to these and other factors the ACGIH has established a TLV-TWA of 0.25 mg/m3, with a skin notation, for dicrotophos. (Ref. 5.4)
In March 1989, OSHA adopted this same value as its PEL.
Editorial Note: These March 1989 PELs were vacated on July 7, 1992 and ceased to be enforceable on March 23, 1993 (FR
1.1.3 Potential workplace exposure
No estimate of worker exposure to dicrotophos could be
found. Dicrotophos is used as a contact and systemic insecticide.
1.1.4 Physical properties (Ref. 5.3-5.5)
no information found
brown liquid (commercial grade)
miscible with water and many organic solvents (i.e., acetone,
alcohol, xylene and isobutanol)
Bidirl, Bidrin, C 709, Carbicron, Diapadrin, Ektafos, ENT
244842, SD 3562
dimethyl cis-2-dimethyl-carbamoyl-1-methylvinyl phosphate
The detection limit of the
analytical procedure is 0.13 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 a split
ratio of 13.4 to 1 used on the capillary GC.
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 polytetrafluoroethylene (PTFE) retainer.
No sampling reagents are required.
2.3 Sampling technique
2.3.1 Attach the small end of the OVS-2 sampling tube to the
2.4 Desorption efficiency
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.
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 at 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 PTFE-lined
Five of these vials were then each liquid spiked
with 27 µL of a 4.37 mg/mL solution of dicrophotos in toluene by
injecting through the septum onto the glass fiber filter. After
replacing the punctured septums, these vials were allowed to equilibrate
overnight in 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 89.8%
2.5 Retention efficiency
Six OVS-2 tubes were each liquid spiked with 27 µL of a 4.37
mg/mL solution of dicrotophos in toluene by spiking the glass fiber filter. These tubes were then
sealed with plastic end caps and placed 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 dicrotophos was found on the backup
sections of these tubes.
Retention Efficiency Study
Average recovery is 91.9%
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
dicrotophos was found in the backup sections of these tubes.
Average recovery is 91.1%
2.7 Recommended air volume and sampling rate
3. Analytical procedure
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 dicrotophos. 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 safety.
2.9.2 Follow all safety practices that apply to the work area being
4. Recommendations for Further Study
3.1.1 A GC equipped with a FPD. A
Hewlett-Packard 589OA 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
dicrotophos from any interference. A 45-m × 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 A 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
3.1.4 Vials, 4-mL and 2-mL glass with PTFE-lined
3.1.5 Volumetric flasks, pipets, and
3.2.1 Hydrogen, air, and nitrogen, GC grade.
3.3 Standard preparation
3.2.2 Toluene, Pesticide grade.
3.2.3 Dicrotophos. A 95% pure standard from EPA was used in this evaluation.
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 dicrotophos. 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 freezer.
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
3.6 Interferences (analytical)
|45-m × 0.2-mm i.d. SE-54, 0.25 µm thick film
2.05 mL/min at 220°C
13.4 to 1 at 220°C
Oven temperature program
|Hydrogen flow rate:
Air flow rate:
Figure 2. Chromatogram of Dicrotophos
This chromatogram also contains other pesticides.
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 and
confirmation by mass spectrometry are additional means of
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 dicrotophos in
each sample from the calibration curve. If dicrotophos 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
||(mg/mL in sample)(desorption volume, mL)
|(air volume, L)(desorption 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.
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 245.
5.3 Windholz, H., Ed.; "Merck Index", 10th ed.; Merck and Co.: Rahway, NJ, 1983; p 449.
5.4 "Documentation of the Threshold Limit Values and Biological Exposure Indices", 5th ed.; American Conference of Governmental
Industrial Hygienists: Cincinnati, OH, 1986; p 193.
5.5 "Farm Chemicals Handbook"; Meister Publishing Co.: Willoughby, OH, 1986; p C82.