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Related Information: Chemical Sampling - Heptachlor


Method number: PV2029
 
Matrix: Air
 
Target Concentration: 0.5 mg/m3 OSHA permissible exposure limit (PEL).
 
Procedure: 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 an electron capture detector (ECD).
 
Recommended air volume
and sampling rate:
60 L at 1.0 L/min
 
Detection limit of the
overall procedure (based
on the recommended air
volume and the analytical
detection limit):
0.49 µg/m3
 
Status of method: Stopgap method. This method has been partially evaluated and is presented for information and trial use only.
   
Date: June 1989 (Final) Chemist: Ing-Fong Chan
   

Organic Methods Evaluation Branch
OSHA Salt Lake Technical Center
Sandy UT 84070-6406

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 device for heptachlor. It follows the procedure developed for chlordane. (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.)

Heptachlor has an acute oral LD50 of 40-188 mg/kg and an acute dermal LD50 of 119-320 mg/kg for rats. (Ref. 5.2. to 5.4.) Animal studies indicating clearly the carcinogenicity in mice and rats have been reported. (Ref. 5.2. to 5.4.) Due to these and other factors the ACGIH has set a threshold limit value (TLV) of 0.5 mg/m3 for heptachlor with a skin notation. (Ref. 5.4.) This level has also been adopted as the OSHA PEL.

1.1.3. Potential workplace exposure

Heptachlor is used as an insecticide. In the United States a total of 2.3 million kg of heptachlor was produced in 1980. (Ref. 5.2.) No information could be found on the number of workers exposed to heptachlor.

1.1.4. Physical properties (Ref. 5.2. to 5.6.)

CAS number: 76-44-8
IMIS number: 1369
Molecular weight: 373.35
Molecular formula:   C10H5Cl7
Boiling point: 135-145°C
Solubility: Practically insoluble in water (0.056 mg/l);
soluble in ethanol (4.5 g/100 ml),
xylene (102 g/100 ml),
carbon tetrachloride (112 g/100 ml),
acetone (75 g/100 ml) and
benzene (106 g/ml).
Chemical name: 1,4,5,6,7,8,8-Heptachloro-3a,4,7,
7a-tetrahydro-4,7-methano-lH-indene
Synonyms:

3-Chlorochlordene; 3,4,5,6,7,8,8a-heptachlorodicyclo-pentadiene; 1,4,5,6,7,8,8-heptachloro-3a,4,7,7a-tetrahydro-4,7-endomethanoindene; 1,4,5,6,7,8,8-heptachloro-3a,4,7,7a-tetrahydro-4,7-methanoindene; 1(3a),4,5,6,7,8,8-heptachloro-3a(1),4,7,7a-tetrahydro-4,7-methanoindene; 3a,4,5,6,7,8,8-heptachloro-3a,4,7,7a-tetrahydro-4,7-methanoindene; 1,4,5,6,7,8,8-heptachloro-3a,4,7,7a-tetrahydro-4,7-methyleneindene; 1,4,5,6,7,10,10-heptachloro-4,7,8,9-tetrahydro-4,7-methyleneindene; 1,4,5,6,7,10,10-heptachloro-4,7,8,9-tetrahydro-4,7-endomethyleneindene
Trade names: Aahepta; Agroceres; Drinox; E 3314; ENT 15,152; GPKh; H34; Heptachlorane; Heptagran; Heptamul; Rhodiachlor; Velsicol 104
Appearance: white, crystalline solid
Structure: structure of heptachlor

1.2. Limit defining parameters

The detection limit of the analytical procedure, including a 17:1 split ratio, is 0.43 pg per injection. This is the 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 o.d. glass tubes that are tapered to 6 mm o.d., packed with a 140-mg backup section, a 270-mg sampling section of cleaned XAD-2 adsorbent and a 13-mm diameter glass fiber filter. The backup section is retained by two foam plugs and the sampling section is between one foam plug and the glass fiber filter. The glass fiber filter is held next to the sampling section by a polytetrafluoroethylene (PTFE) retainer. (Figure 1)

2.2. Reagents

No sampling reagents are required.

2.3. Sampling technique

2.3.1. Immediately before sampling, remove the plastic end caps from the OVS-2 tube.

2.3.2. Attach the small end of the tube to the sampling pump with flexible tubing.

2.3.3. Attach the tube vertically in the employee's breathing zone in such a manner that it does not impede work performance.

2.3.4. After sampling for the appropriate time, remove the tube and seal with plastic caps.

2.3.5. Wrap each sample end-to-end with an OSHA seal (Form 21).

2.3.6. Record the air volume for each sample, and list any possible interferences.

2.3.7. Submit at least one blank for each set of samples. Handle the blank in the same manner as the samples, except no air is drawn through it.

2.3.8. Submit bulk samples for analysis in a separate container. Limit the amount of bulk submitted to one gram or one ml. Do not ship them with air samples.

2.4. Desorption efficiency (glass fiber filter and XAD-2 adsorbent)

Fifteen vials, each containing a 13-mm glass fiber filter and 270-mg of XAD-2 adsorbent, were each liquid spiked on the glass fiber filter with a 2.95 mg/ml solution of heptachlor. The first five filters were each spiked with 5 µl (.5× PEL) of the solution. The second five were each spiked with 10 µl (1× PEL) and the remaining five were each spiked with 20 µl (2× PEL) of the solution. These vials were allowed to sit overnight at ambient temperature, desorbed with 4.0 mL of toluene, shaken for 30 min and then analyzed as in Section 3. The results are listed in Table 2.4.

Table 2.4.
Desorption Efficiency



Sample #
Amount
Spiked, µg
Amount
Found, µg
%
Recovered

D1
D2
D3
D4
D5
14.80
14.80
14.80
14.80
14.80
14.12
15.05
13.84
14.77
15.88
95.4
101.7
93.5
99.8
107.3

D6
D7
D8
D9
D10
29.50
29.50
29.50
29.50
29.50
29.50
30.78
30.48
30.58
30.83
100.0
104.3
103.3
103.7
104.5

D11
D12
D13
D14
D15
59.00
59.00
59.00
59.00
59.00
58.30
58.86
58.73
58.61
58.69
98.8
99.8
99.5
99.3
99.5

Average of .5× PEL =
Average of  1× PEL =
Average of  2× PEL =
99.5
103.2
99.4



2.5. Retention efficiency

Six OVS-2 tubes were each liquid spiked with 20 µl (2× PEL) of a 2.95 mg/ml solution of heptachlor in toluene. These were allowed to dry for 2 hours and then 60 L of humid air (~80% relative humidity) were drawn through each tube at 1 L/min. The tubes were stored overnight in a drawer at ambient temperature, desorbed with 4.0 mL of toluene, shaken for 30 min and then analyzed as in Section 3. The results are listed in Table 2.5.

Table 2.5.
Retention Efficiency



Sample #
Amount
Spiked, µg
Amount
Found, µg
%
Recovered

R1
R2
R3
R4
R5
R6
59.00
59.00
59.00
59.00
59.00
59.00
58.17
57.02
58.77
58.57
58.07
59.21
98.6
96.6
99.6
99.3
98.4
100.4

Average = 98.8

2.6. Sample storage

Twenty four OVS-2 tubes were each liquid spiked with 10 µl (1× PEL) of 2.95 mg/ml of heptachlor. These were allowed to dry for 2 hours and then 60 L of humid air (~80% relative humidity) were drawn through each tube at 1 L/min. Half of the tubes were stored in a drawer at ambient temperature, and the other half were stored in a freezer (-5°C). They were extracted and analyzed as in Section 3. The results are given in Tables 2.6.1. and 2.6.2.

Table 2.6.1.
Retention Efficiency


Days
Stored
Amount
Spiked, µg
Amount
Found, µg
%
Recovered

0
0
0
29.50
29.50
29.50
28.99
28.99
29.72
98.3
98.3
100.7

4
4
4
29.50
29.50
29.50
26.32
28.77
29.53
89.2
97.5
100.1

7
7
7
7
7
7
29.50
29.50
29.50
29.50
29.50
29.50
28.14
29.06
29.54
28.77
28.78
29.88
95.4
98.5
100.1
97.5
97.6
101.3

Average of 0 days =
Average of 4 days =
Average of 7 days =
99.1
95.6
98.4

Table 2.6.2.
Freezer Storage


Days
Stored
Amount
Spiked, µg
Amount
Found, µg
%
Recovered

0
0
0
29.50
29.50
29.50
29.48
28.09
29.67
99.9
95.2
100.6

4
4
4
29.50
29.50
29.50
27.53
29.35
25.47
93.3
99.5
86.3

7
7
7
7
7
7
29.50
29.50
29.50
29.50
29.50
29.50
29.55
29.93
30.53
29.86
29.68
29.13
100.2
101.5
103.5
101.2
100.6
98.7

Average of 0 days =
Average of 4 days =
Average of 7 days =
  98.6
  93.0
100.9

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 heptachlor. Any suspected interferences should be reported to the laboratory.

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. A balance capable of weighing to the nearest tenth of a milligram. A Mettler HL52 balance was used in this evaluation.

3.1.2. A mechanical shaker.

3.1.3. A GC equipped with an ECD. A Hewlett Packard (HP) 5890 equipped with an autosampler was used in this evaluation.

3.1.4. A GC column capable of separating heptachlor from any interferences. A 45 m × 0.25 mm i.d. (0.25 µm film) SE-54 capillary column was used in this evaluation.

3.1.5. An electronic integrator, or some other suitable means for measuring detector response. The Hewlett-Packard 3357 Laboratory Data System was used in this evaluation.

3.1.6. Volumetric flasks and pipets.

3.1.7. Vials, 2-mL, and 4-mL.

3.2. Reagents

3.2.1. Toluene, reagent grade.

3.2.2. Heptachlor, reagent grade. A standard obtained from EPA (EPA # 3860, 99.8% purity) was used in this evaluation.

3.3. Standard preparation

Prepare stock standards by adding toluene to preweighed amounts of heptachlor. Prepare working range standards by diluting stock standards with toluene. Store stock and working 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 4-mL 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 4.0 mL of toluene to each vial and seal with a Teflon-lined cap.

3.4.3. Shake the vials for 30 minutes on a mechanical shaker.

3.4.4. If necessary, transfer the samples to 2-mL vials for use on an HP autosampler.

3.5. Analysis

3.5.1. Instrument conditions

Column: SE-54, 45 m × 0.25 mm i.d., 0.25 µm film
Injector temperature: 250°C
Column temperature: 230°C
Detector temperature: 300°C
Gas flows:
    Column:
    ECD make up:

2.14 mL/min hydrogen
20 mL/min nitrogen
Injection volume: 1 µL
Split ratio: 17:1
Retention time: 6.75 min

3.5.2. Chromatogram (Figure 2)

3.6. Interferences (analytical)

3.6.1. Any collected compound having a similar retention time to that of the analyte is a potential interference.

3.6.2. GC conditions may generally be varied to circumvent interferences.

3.6.3. Retention time on a single column is not proof of chemical identity. Analysis by an alternate GC column, high performance liquid chromatography (HPLC) 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 (µg/mL) of heptachlor.

3.7.2. Determine the µg/mL of heptachlor in both sections of each sample and blank from the calibration curve.

3.7.3. Blank correct each sample by subtracting the µg/mL found in each section of the blank from the µg/mL found in the corresponding sections of the sample and then add the two sample sections together.

3.7.4. Determine the air concentration by using the following formula.

mg/m3 = (µg/mL, blank corrected) × (desorption volume, mL)
(air volume, L) × (desorption efficiency, decimal)

3.8. Safety precautions (analytical)

3.8.1. Avoid skin contact and air exposure to heptachlor.

3.8.2. Avoid skin contact with all solvents.

3.8.3. Wear safety glasses at all times.

4. Recommendation for Further Study

This method should be fully validated.

sampling tube

Figure 1. OVS-2 Sampling Device

chromatogram of heptachlor

Figure 2. Chromatogram of Heptachlor

5. References

5.1. Burright, D.; Method #67, "Chlordane (Technical Grade)"; OSHA Analytical Laboratory, 1987; unpublished.

5.2. IARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans; International Agency for Research on Cancer: Lyon, 1979; Vol. 20, pp 129-153.

5.3. Registry of Toxic Effects of Chemical Substances 1985-86 Edition; DHHS(NIOSH) Publication No. 87-114, U.S. Department of Health and Human Services: Cincinnati, OH, 1987; Vol. 3A, p 3060-146.

5.4. Documentation of the Threshold Limit Values and Biological Exposure Indices, American Conference of Governmental Industrial Hygienist INC., fifth edition, 1986; p 296.

5.5. Farm Chemicals Handbook; Berg, Gordon L. Ed.; Meister: Willoughby, Ohio, 1986; p C123.

5.6. Merck Index, 10th ed.; Windholz, Martha ED.; Merck: Rahway, N.J., 1983; p 673.