1. General Discussion
1.1 Background
1.1.1 History of procedure
This evaluation was undertaken to determine the effectiveness of the OVS-2 tube as a sampling
diuron and to analyze samples. It follows the developed for carbaryl. (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).
Herbicides are weed killers with either general or selective applications in agriculture. Herbicides
interfere with plant chemistry and physiology. They may inhibit plant
respiration and photosynthesis, as well as plant physiology by mimicking growth regulators or interfering with their synthesis or action.
Diuron is a herbicide whose chemical class is phenyl urea. It has been shown to inhibit plant photosynthesis by blocking light reaction II. Hence light is
required to elicit its phytotoxic effects. This herbicide demonstrates low acute toxicity toward mammals.
(Ref. 5.2)
The following paragraph describing the toxicity is excerpted from the book
Documentation of the Threshold Limit Values And Biological Exposure
Indices (Ref. 5.3)
Hodge and co-workers have reported a low order of acute and chronic toxicity for
diuron.
The oral LD5O for male rats was given at 3400 mg/kg. No -effect dietary concentration
levels in two-year feeding studies are considered to be 250 ppm for rats and 125 ppm for
dogs. A dietary concentration of 125 ppm did not adversely affect reproduction in a three-generation rat study. There was no evidence of carcinogenicity in these chronic studies or in
an 18-month study on mice at approximately 1400 ppm.
The following paragraph describing the harm and symptoms of diuron were taken from the
Handbook of Toxic and Hazardous Chemicals and Carcinogens. (Ref. 5.4)
The concentrated material may cause irritation to the eyes and mucous membranes, but
a 50% water paste was not irritating to the intact skin of guinea pigs.
Due to these factors diuron has been given a TLV-TWA of 10 mg/m3 by the
ACGIH. (Ref.
5.3)
OSHA adopted this same value as its PEL in March 1989.
Editorial Note: These March 1989 PELs were vacated on July 7, 1992 and ceased to be enforceable on March 23, 1993 (FR 58:35338-35351, 6/30/1993).
1.1.3 Potential workplace exposure
No estimate of worker exposure to diuron could be found. Potential exposure involves those individuals
in manufacturing, formulation, and application of the herbicide. (Ref. 5.4)
1.1.4 Physical Properties (Ref. 5.2-5.7)
Molecular weight: |
233.10 |
Molecular Formula: |
C9H10Cl2N2O |
CAS #:
|
330-54-1 |
IMIS #: |
2684 |
Melting point: |
158 to 159°C |
Vapor Pressure: |
0.0041 Pa (0.000031 mmHg) at 30°C |
Appearance: |
white crystalline solid |
Solubility: |
42 ppm in water at 25°C, 5.3% at 27°C, very low so'. hydrocarbon solvents |
Synonyms: |
Cekiuron, Crisuron, Dailon, Diater Di-on, Direx4L,
Diurex, Diurol Dynex, Karmex, Rout, Unidron, Urox Vonduron, dichlorfenidim
(USSR) |
Chemical names: |
3-(3,4-Dichlorophenyl)-1,1-dimethylurea;
N'-(3,4-dichlorophenyl)-N,N-dimethylurea |
UV spectrum: |
![Please note: For problems with accessibility in using figures and illustrations in this method, please contact the author at (801) 233-4900. Please note: For problems with accessibility in using figures and illustrations in this method, please contact the author at (801) 233-4900.](fig_1.jpg) |
Stability: |
Sunlight (ultraviolet irradiation) degrades
diuron. Decomposes on heating (180-190°C) yielding dimethylamine and
3,4-dichlorophenylisocyanate. |
Structural Formula:
1.2 Limiting defining parameters
The detection limit of the analytical procedure is 1.81 ng per injection. This is the amount of
amount of analyte which will give a peak whose height is approximately five times the baseline
noise.
2. Sampling Procedure
2.1 Apparatus
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 tubes 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.
![Please note: For problems with accessibility in using figures and illustrations in this method, please contact the author at (801) 233-4900. Please note: For problems with accessibility in using figures and illustrations in this method, please contact the author at (801) 233-4900.](https://webarchive.library.unt.edu/eot2008/20081106054929im_/http://www.osha.gov/dts/sltc/methods/images/ovs_2.gif)
polytetrafluoroethylene (PTFE) retainer |
2.2 Reagents
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 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 any bulk samples in a separate container. Do not ship them with the air samples.
2.4 Extraction efficiency
Three OVS-2 tubes were each liquid spiked with 31 µL (1/20 PEL) of a 0.9627 mg/mL solution of diuron in
acetonitrile. Three additional OVS-2 tubes were each liquid spiked with 62
µL (1/10 PEL) of the above diuron standard. These tubes were allowed to sit
overnight on a desk at ambient temperature and then extracted with 5.0 mL of acetonitrile and analyzed as in Sections
3.4 and 3.5.
Table 2.4
OVS-2 Extraction Study |
Tubes # |
1/20 PEL |
1/10 PEL |
|
|
|
|
OVS1 |
96.6%
|
86.6% |
OVS2 |
88.1% |
96.3% |
OVS3 |
91.7% |
95.0% |
|
Averages |
92.1% |
92.6% |
2.5 Retention efficiency
Four OVS-2 tubes were each liquid spiked with 62 µL of a 0.9627 mg/mL solution of diuron by spiking the glass fiber filter.
Sixty liters of humid air (approximately 70% relative humidity) were drawn through each tube. Three of these tubes were then
desorbed and analyzed as in Sections 3.4 and 3.5. No diuron was recovered
from the backup section of these tubes. The fourth tube had 120 liters of humid air drawn through it and had a recovery
of 91.9%.
Table 2.5
Retention Efficiency Study
|
Tube # |
Recovery |
|
RET1 |
95.6% |
RET2 |
91.0% |
RET3 |
95.5% |
|
Average recovery
is 94.0% |
2.6 Sample storage
Eighteen OVS-2 tubes were each liquid spiked with 62 µL of
a 0.9627 mg/mL solution of diuron by placing it on the glass fiber filter. Sixty liters of humid air (approximately
70% relative humidity) were drawn through each tube. Half of the tubes were
stored in a drawer at ambient temperature, and the other half were stored in a refrigerator
(2°C). They were stored according to Table 2.6 and extracted and analyzed as in
Section 3.4 and 3.5. No diuron was recovered from the backup section of
these tubes.
Table 2.6
Storage Study
|
Days |
Ambient |
Averages |
Refrigerator |
Averages |
|
|
|
|
|
|
0 |
95.7% |
96.2% |
96.2% |
96.3% |
|
97.1% |
|
96.7% |
|
|
95.9% |
|
96.1% |
|
|
|
|
|
|
7 |
94.2% |
94.4% |
95.3% |
95.0% |
|
93.3% |
|
95.0% |
|
|
95.6% |
|
94.8% |
|
|
|
|
|
|
14 |
94.1% |
92.5% |
96.2% |
95.7% |
|
91.6% |
|
95.8% |
|
|
91.7% |
|
95.0% |
|
|
Average recovery (ambient) 94.4%
Average recover (refrigerator) 95.7%
2.7 Recommended air volume and sampling rate
2.7.1 The recommended air volume is 60 L.
2.7.2 The recommended flow rate is 1.0 L/min.
2.8 Interferences (sampling)
It is not known if any compounds will interfere with the
collection of diuron. 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 sampled.
3. Analytical Procedure
3.1 Apparatus
3.1.1 An HPLC equipped with a UV detector and a manual or automatic injector. A Waters 600 pump, Waters 712
autosampler and Waters 490E UV detector were used in this evaluation.
3.1.2 An HPLC column capable of separating diuron from any
interferences. A (8-cm x 6.2-mm i.d.) Golden Series Zorbax ODS (3 micron) 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 and 20-mL glass with capped or PTFE-lined
septa.
3.1.5 Volumetric flasks, pipets, and syringes.
3.2 Reagents
3.2.1 Acetonitrile, HPLC grade.
3.2.2 Water, HPLC grade. A Millipore Milli-Q system was
used to prepare the water in this evaluation.
3.2.3 Diuron. A 99.25% pure standard from EPA was used in
this evaluation.
3.3 Standard preparation
Prepare stock standard solutions by adding acetonitrile to
pre-weighed amounts of diuron. Prepare working range standards by
diluting stock solutions with acetonitrile. 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 OVS-2 tube to a 20-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 5.0 mL of acetonitrile to each vial.
3.4.3 Seal the vials and shake them for half an hour on a
mechanical shaker.
3.4.4 Transfer an aliquot of sample to the 4-mL vial and
seal with PTFE-lined septa.
3.5 Analysis
3.5.1 Liquid chromatographic conditions
Column: |
8-cm x 6.2-mm i.d. stainless steel Golden Series column
packed with 3 micron Zorbax ODS |
Mobile Phase: |
55% acetonitrile / 45% water |
Flow Rate: |
1 mL/min |
UV detector: |
254 nm |
Retention time: |
5.44 min |
Injection volume: |
15 µL |
3.5.2 Chromatogram
![Please note: For problems with accessibility in using figures and illustrations in this method, please contact the author at (801) 233-4900. Please note: For problems with accessibility in using figures and illustrations in this method, please contact the author at (801) 233-4900.](https://webarchive.library.unt.edu/eot2008/20081106054929im_/http://www.osha.gov/dts/sltc/methods/partial/pv2097/fig03.jpg)
Figure 3. Chromatogram of Diuron |
3.6 Interferences (analytical)
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 HPLC column, detection at another wavelength (for
comparison of absorbance response ratios) and confirmation by mass spectrometry are additional means
of identification.
3.7 Calculations
3.7.1 Construct a calibration curve by plotting detector response versus standard concentration.
3.7.2 Determine the concentration of diuron in each sample
from the calibration curve. If diuron 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.
mg/m3 = |
(µg/mL, blank corrected) x (extraction volume, mL)
(air volume, L) x (extraction efficiency, decimal) |
3.8 Safety precautions (analytical)
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.
4. Recommendations for Further Study
4.1 A better desorption solvent than acetonitrile might be
found.
4.2 This method should be fully validated.
4.3 This method has been partially evaluated at 60 liters or
air at 1 liter per minute; however, since the PEL of diuron is high and its
solubility is low, it might be better to lower the sampling rate to 200 cc/min to prevent the sampling tube from
becoming clogged with diuron.
5. References
5.1 Burright, D.; Method #63, "Carbaryl"; OSHA Analytical
Laboratory unpublished, 1987.
5.2 Cawse, J.N.; "Kirk-Othmer Encyclopedia of Chemical
Technology", 3rd ed.; John Wiley and Sons: New York, NY., 1980; Vol.
12, pp 297-322.
5.3 Documentation of the Threshold Limit Values and
Biological Exposure Indices", 5th ed.; American Conference of Governmental
Industrial Hygienists: Cincinnati, OH, 1986; p 228.
5.4 Sittig, M.; "Handbook of Toxic and Hazardous Chemical
and Carcinogens", 2nd ed.; Noyes Publication: Park Ridge, NJ., 1985; p
394.
5.5 "Farm Chemicals Handbook"; Meister Publishing Co.:
Willoughby, OH, 1986; p C88.
5.6 "Merck Index", 10th ed.; Windholz, M., Ed.; Merck and
Co.: Rahway, NJ, 1983; p 494.
5.7 Cawse, J.N.; "Kirk-Othmer Encyclopedia of Chemical
Technology", 3rd ed.; John Wiley and Sons: New York, NY., 1980; vol. 21
pp 273-276.
|