CYPERMETHRIN

Organic Service Branch II 
OSHA Salt lake Technical Center 
Salt Lake City, Utah 

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 cypermethrin. It follows the procedure developed for pyrethrum (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) 

Besides being absorbed following inhalation or ingestion, cypermethrin is readily adsorbed through the intact skin (Ref. 5.2). When a particular pesticide has a low dermal LD 501 a skin notation should be added to the TLV or PEL.

Cypermethrin has an acute oral LD₅₀, of 70 mg/Kg and acute dermal LD₅₀ of 500 mg/Kg for rats (Ref. 5.4). 

Due to these factors an arbitrary target concentration of 1.0 mg/m³ with a skin notation, was chosen for cypermethrin. 

1.1.3 Potential workplace exposure

Cypermethrin is an insecticide/pesticide used to 
control insects on ornamental plants, vegetables, 
fruits, farm crops, and on pets. Can also be used for termite control. No data is available on the extent of work place exposure (Ref. 5.3). 

1.1.4 Physical properties (Ref. 5-3, 5.4 and 5.5) 

CAS number:	52315-07-8
IMIS number:	C628
Molecular weight:	416.3
Molecular formula:	C22H19CL2NO3
Melting point:	60 to 80°C at 101.3 kPa (760 mmHg)
Solubility:	insoluble in water  soluble in methanol, acetone, xylene, methylene chloride
Synonyms:	cypermethrin
Chemical name:	3-(2,2-Dichloroethenyl)-2,2,-di- methylcyclopropanecarboxylic acid cyano (3-phenoxyphenyl) methyl ester
Trade names:	Cypercopal, Cyperkill, Cyperma
Appearance:	colorless crystals (pure isomer)
Structure:

 

1.2 Limit defining parameters 

The detection limit of the analytical procedure, including a 
11:1 split ratio, is 0.012 ng 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 sample is 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 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 XAD-2 adsorbent. 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. These tubes are commercially available (i.e., SKC, Supelco). 

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 employee'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 Record the air volume for each sample and list any possible interferences. 

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

2.3.7 Submit any bulk samples for analysis in a separate container. Do not ship bulk samples with the air samples. 

2.4 Desorption efficiency
 
A 13-mm glass fiber filter and a amount of XAD-2 adsorbent equal to the sampling section (270 mg) of an OVS-2 tube were placed in each of eighteen 4-mL vials. They were divided into three groups of six vials. These groups were liquid spiked respectively with 22, 12 and 2 µL of 2.65 mg/mL solution of cypermethrin in toluene by spiking the glass fiber filter. These amounts represent 1.0×, 0.5×, and 0.l× the target concentration. They were then sealed with PTFE-lined septa and allowed to equilibrate overnight in a drawer at room temperature. The vials, along with a blank vial, were desorbed with 3.0 mL of the desorbing solution, and analyzed as in Section 3. The average desorption efficiency was  97.03%. The results are listed in Table 2.4. 

2.5 Retention efficiency

Six OVS-2 tubes were each liquid Spiked with 22 µL (l× TC) of 2.65 mg/mL solution of cypermethrin in toluene by spiking the glass fiber filter. These were allowed to equilibrate overnight In a drawer at room temperature and then 60 L of humid air (~80% relative humidity) were drawn through each tube at 1.0 L/min. The tubes, along with a blank tube, were desorbed with 3.0 mL of desorbing solution, and analyzed as in Section 3. No analyte was observed in backup sections. The results are listed in Table 2.5. 

2.6 Sample storage
 
Twelve OVS-2 tubes were each liquid spiked with 22 µL (1× TC) of a 2.65 mg/mL solution in toluene by spiking the glass fiber filter. These tubes were allowed to equilibrate overnight in a drawer at room temperature and then 60 L of humid air (80% relative humidity) were drawn through each tube at 1.0 L/min. The twelve tubes were divided into two groups of six tubes each. The first group was stored in a drawer at ambient temperature, the second group was stored in a freezer (-5°C). After fifteen days they were extracted and analyzed as in Section 3. No analyte was observed in backup sections. The results are given in Tables 2.6.1, and 2.6.2. 

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 cypermethrin. Any 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 A GC equipped with an ECD. A Hewlett-Packard 5890A GC 
(capillary) equipped with both an ECD and a Hewlett-Packard 7673A Autosampler was used in this evaluation.

3.1.2 A GC column capable of separating cypermethrin from any interferences. A 45 m x 0.32 mm i.d. (0.25 um film) SE-30 capillary column was used in this evaluation. 

3.1.3 An electronic integrator or some other suitable means to measure detector response. A Waters 860 Networking Computer System was used in this evaluation. 

3.1.4 Volumetric flasks, pipets, and syringes for preparing standards, making dilutions and performing injections. 

3.1.5 Vials, 2-mL, and 4-mL, with PTFE-lined caps. 

3.1.6 Mechanical shaker. 

3.2 Reagents

3.2.1 Cypermethrin. A 99% pure standard from EPA was used in this evaluation. 

3.2.2 Toluene. The toluene used in this evaluation was purchased from Burdick and Jackson.

3.2.3 p-Chlorobiphenyl.  The p-chlorobiphenyl was purchased from ICN. 

3.2.4 Desorbing solution. If an internal standard (ISTD) is used, the desorbing solution is prepared by adding 8 µL 
of p-chlorobiphenyl to 100 mL of toluene. Otherwise, toluene can be used.

3.3 Standard preparation 

Prepare stock standards by adding desorbing solution to preweighed amounts of cypermethrin. Prepare working range 
standards by diluting stock solutions with desorbing solution. 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 after it has been cleaned by surfactant or solvent washing.

3.4.2 Add 3.0 mL of desorbIng solution to each vial and seal with a PTFE-lined cap.

3.4.3 Shake the vials on a mechanical shaker for half an hour.

3.4.4 If necessary, transfer aliquots of the samples to the appropriate GC vials. 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 Analysis

3.5.1 Instrument conditions 

Column: Injector temperature: Detector temperature: Column temperature: Head pressure: FPD conditions:  hydrogen flow rate: Injection volume: Split ratio: Retention time:

SE-30, 45 m × 0.32 mm i.d., 0.25 µm film 25°C 300°C 230°C  12 psi 2 mL/min 1 µL 11:1  4 Distinctive peaks of cypermethrin ( Rt. window 9.9 - 10.4)

3.5.2 Chromatogram

Figure 2. Chromatogram of cypermethrin.

3.5.3 Measure detector response using a suitable method such as electronic integration.

3.6 Interferences (analytical) 

3.6.1 Any collected compound which produces an ECD response and has a similar retention time as cypermethrin 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 A calibration curve may be constructed by plotting concentration of analyte per mL versus response of standard concentration (ug/mL) of cypermethrin. Cypermethrin has 8 possible isomers, standard used have 4 distinctive peaks. Therefore peak summation is advised for calculation. Bracket the samples with prepared analytical standards over a range of concentrations.

3.7.2 Determine the pg/mL of cypermethrin in both sections of each sample and blank from the calibration curve. If cypermethrin is found on the backup section, It is added to the amount found on the front section. Blank corrctions should be performed before adding the results together.

3.7.3 Determine the air concentration by using the following formula. 

 
where 24.46 = molar volume (liters) at 101.3 kPa (760 mmHg) and 25°C

416.3 = molecular weight of cypermethrin 

3.8 Safety precautions (analytical)

3.8.1 Avoid skin contact and air exposure to cypermethrin. 

3.8.2 Avoid skin contact with all solvents. 

3.8.3 Wear safety glasses in laboratory. 

4. Recommendation for Further Study 

This method should be fully validated.

5. References

5.1 Burright, D.; Methods #70s "PYRETHRUM"; OSHA Analytical Laboratory, published, 1988. 

5.2. "OCCUPATIONAL DISEASE, A Guide to their Recognition"; U.S. Department of Health, Education, and Welfare; Public Health Ser- vice, Public Health Service Publication No. 1097, U.S. Government Printing Office: Washington, D.C., 1964; p 245. 

5.3 Material safety data sheet, OCCUPATIONAL HEALTH SERVICES.

5.4 "Farm Chemicals Handbook"; Meister Publishing Co.: Willoughby, OH, 1990; PP C99-100. 

5.5 Windholz, H., Budavari, S., Blumetti, RF., and Otterbeint Lr., The Merck Index, 11th ed., Merck & CO., Inc., Rahway, N.J., 1983; p 434.