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Related Information: Chemical Sampling - Phenothiazine


Method no.: PV2048
   
Matrix: Air
   
Target concentration: 5 mg/m3 (OSHA TWA PEL)
   
Procedure: Samples are collected by drawing a known volume of air through a glass fiber filter. Samples are extracted with methyl tert-butyl ether and analyzed by gas chromatography with a nitrogen-phosphorous detector (GC-NPD). Samples should be protected from sunlight.
   
Air volume and sampling
rate studied:
100 liters at 1.0 liters per minute.
   
Status of method: Stopgap method. This method has been only partially evaluated and is presented for information and trial use.
   
October 1989
Mary E. Eide
Solvents Branch
OSHA Analytical Laboratory
Salt Lake City, UT

1. General Discussion

1.1. Background

1.1.1. History of procedure

The PEL for phenothiazine is 5 mg/m3. Since phenothiazine is a solid at room temperature, collection on a glass fiber filter was tried and found successful. There was no loss of phenothiazine in the retention studies. The extraction, and storage studies were near 100%.

1.1.2. Potential workplace exposure (Ref. 5.1.)

Phenothiazine is used as a pesticide, and is used orally to treat pinworm, threadworm, and roundworm infestations. It is used as a base for the manufacture of pharmaceuticals. It is used as a urinary antiseptic.

1.1.3. Toxic Effects (This section is for information purposes and should not be taken as the basis for OSHA policy.)(Ref. 5.1.)

Oral doses of 1 or more grams per day may cause toxic hepatitis, hemolytic anemia, abdominal cramps, tachycardia, gastrointestinal and skin irritation, skin photosensitization, kidney damage, and pruritus. Workers applying phenothiazine in orchards reported skin irritation, including itching, and redness on any exposed surface. The photosensitizing dose is less than 0.75 grams. Workers exposed to between 15 and 48 mg/m3 during pulverizing and packaging phenothiazine dust developed pinkish-red hair, brown fingernails, and skin irritation.

1.1.4. Physical properties (Ref. 5.2.):

Compound: Structural Formula
Synonyms: dibenzothiazine; Agrazine; thiodiphenylamine; Biverm; Antiverm; Contaverm; Ieeno; ENT 38; Fenoverm; Fentiazine; Helmetina; Lethelmin; Nemazene; Orimon; Padophene; Penthazine; Vermitin; XL-50; Wurm-thional; Souframine
Molecular weight: 199.26
Melting point: 185C
Boiling point: 371C
Color: yellow rhombic leaflets or diamond-shaped plates
Molecular formula: C12H9NS
CAS: 92-84-2
IMIS: 2041
RTECS: 57228 (SN5075000)

1.2. Limit defining parameters

1.2.1. The detection limit of the analytical procedure is 1 ng. This is the smallest amount that could be detected under normal operating conditions.

1.2.2. The overall detection limit is 0.03 mg/m3, based on a 3 mL extraction and a 100 liter air volume. (All mg/m3 amounts in this study are based on a 100 liter air volume and a 3 mL desorption.)

1.3. Advantages

1.3.1. The sampling procedure is convenient.

1.3.2. The analytical method is reproducible and sensitive.

1.3.3. Reanalysis of samples is possible.

1.3.4. It may be possible to analyze other compounds at the same time.

1.3.5. Interferences may be avoided by proper selection of column and GC parameters.

1.4. Disadvantages

none known

2. Sampling procedure

2.1. Apparatus

2.1.1. A calibrated personal sampling pump, the flow of which can be determined within + 5% at the recommended flow.

2.1.2. A three-piece cassette containing a 37 mm glass fiber filter with a back-up pad.

2.2. Sampling technique

2.2.1. The ends of the filter cassette are opened immediately before sampling.

2.2.2. Connect the filter cassette to the sampling pump with flexible tubing.

2.2.3. Air being sampled should not pass through any hose or tubing before entering the cassette.

2.2.4. Seal the ends of the cassette with plastic caps immediately after sampling. Seal each sample lengthwise with OSHA Form-21 sealing tape.

2.2.5. With each batch of samples, submit at least one blank filter from the same lot used for samples. This filter should be subjected to exactly the same handling as the samples except that no air is drawn through it.

2.2.6. Transport the samples (and corresponding paperwork) to the lab for analysis.

2.2.7. Bulks submitted for analysis must be shipped in a separate mailing container from the samples.

2.3. Extraction efficiency

Six glass fiber filters were liquid spiked at each loading of 16.56 g (0.4968 mg/m3), 82.8 g (2.484 mg/m3), and 165.6 g (4.968 mg/m3) phenothiazine. They were allowed to equilibrate overnight at room temperature. They were opened, placed into a 4 mL vial, extracted with 3 mL of methyl t-butyl ether, for 30 minutes with occasional shaking, and were analyzed by GC-NPD. The overall average was 99.8 % recovered (Table 1).

Table 1
Desorption Efficiency


Tube# % Recovered
16.56 g 82.8 g 165.6 g

1 99.1 99.9 98.7
2 97.1 101 101
3 103 99.6 lost
4 101 102 101
5 99.0 99.4 101
6 97.9 98.9 99.6

average 100 100 99.5

overall average 99.8
standard deviation 1.51

2.4. Retention efficiency

Six glass fiber filters were liquid spiked with 165.6 g (4.968 mg/m3) phenothiazine. They were placed in a cassette with a second glass fiber filter, and a spacer between the two filters. They were allowed to equilibrate overnight , and had 100 liters humid air (90% RH) pulled through them. They were opened, extracted, and analyzed by GC-NPD. There was no phenothiazine found on the second glass fiber filter (Table 2). The retention efficiency averaged 99.1 %.

Table 2
Retention Efficiency


Sample # % Recovered % Recovered Total
'A' 'B'

1 99.3 0.0 99.3
2 97.8 0.0 97.8
3 101 0.0 101
4 98.6 0.0 98.6
5 100 0.0 100
6 98.0 0.0 98.0

average 99.1

2.5. Storage

Glass fiber filters were spiked with 165.6 g (4.968 mg/m3) phenothiazine and stored at room temperature on the benchtop until opened and analyzed. Half of the storage samples were stored in brown vials, as phenothiazine decomposes in sunlight. The storage samples were exposed to room light. There was little difference between the samples stored in brown and clear glass. The spectrum of room light does not compare to sunlight, so this comparison probably does not mimic sunlight conditions. The recoveries averaged 98.9% for brown glass vials, and 99.6 % for clear glass vials for the 14 days stored (Table 3).

Table 3
Storage Study


Days % Recovered
brown glass clear glass

6 102 102
6 99.7 99.0
6 100 101
14 98.3 98.1
14 97.2 98.2
14 96.2 99.5

average 98.9 99.6
overall average 99.3

2.6. Precision

The precision was calculated using the area counts from six injections of each standard at concentrations of 16.56, 82.8, 165.6, and 331.2 g/mL. The pooled coefficient of variation was 0.0152 (Table 4).

Table 4
Precision Study


Injection 16.56 82.8 165.6 331.2
Number g/mL g/mL g/mL g/mL

1 17172 89354 200460 364060
2 17032 86143 198930 357320
3 16878 85210 205780 353010
4 17103 85358 204320 355600
5 17013 88439 207290 355490
6 16917 88699 200900 350190

Average 17019 87201 202947 355945

Standard
Deviation 110 1838 3325 4686

   CV 0.00646 0.0211 0.0164 0.0132

Pooled CV 0.0152

where:

formula for pooled coefficient of variation

A(1), A(2),A(3),A(4) = # of injections at each level
CVl, CV2, CV3, CV4 = Coefficients at each level

2.7. Air volume and sampling rate studied

2.7.1. The air volume studied is 100 liters.

2.7.2. The sampling rate studied is 1.0 liter per minute.

2.8. Interferences

Suspected interferences should be listed on sample data sheets.

2.9. Safety precautions

2.9.1. Sampling equipment should be placed on an employee in a manner that does not interfere with work performance or safety.

2.9.2. Safety glasses should be worn at all times.

2.9.3. Follow all safety practices that apply to the workplace being sampled.

3. Analytical method

3.1. Apparatus

3.1.1. Gas chromatograph equipped with a nitrogen-phosphorous detector. An HP 5890 gas chromatograph was used for this study. Phenothiazine can also be analyzed by gas chromatography with a flame photometric detector in the sulfur mode, with a detection limit of 0.2 mg/m3.

3.1.2. GC column capable of separating the analyte from any interferences. The column used in this study was a 60 M RTX-5 capillary column with a 0.32 mm I.D. and a 1.5 df. Other columns that can be used are a 60 M RTX-1 capillary column with a 0.32 mm I.D. and a 1.0 df, or a 30 M DB-210 capillary column with a 0.32 mm I.D. and a 0.5 df.

3.1.3. An electronic integrator or some other suitable method of measuring peak areas.

3.1.4. Two and four milliliter vials with Teflon-lined caps. The samples are extracted in 4 mL vials, and transferred to the 2 mL vials for analysis.

3.1.5. A 10 L syringe or other convenient size for sample injection.

3.1.6. 3 mL pipets for dispensing the methyl tert-butyl ether.

3.1.7. Volumetric flasks - 10 mL and other convenient sizes for preparing standards.

3.1.8. Analytical balance capable of weighing milligram amounts.

3.2 Reagents

3.2.1. Purified GC grade nitrogen, hydrogen, and air.

3.2.2. Methyl tert-butyl ether, HPLC grade.

3.2.3. Phenothiazine, Reagent grade

3.3. Sample preparation

3.3.1. Sample cassettes are opened and the filter is placed in a 4 mL vial.

3.3.2. The filter is extracted with 3 mL of methyl t-butyl ether.

3.3.3. The vials are sealed immediately and allowed to extract 30 minutes with occasional shaking.

3.3.4. An aliquot is placed in a 2 mL vial for analysis.

3.4. Standard preparation

3.4.1. Standards are prepared by diluting a known quantity of phenothiazine with methyl tert-butyl ether. Two different stock standards should be prepared, and dilutions of them made.

3.4.2. A series of standards are prepared covering the range from detection limit to the highest sample. At least five different concentrations should be made so that there are enough data points to plot a curve. The range used in this study was 1.656 to 165.6 g/mL.

3.5. Analysis

Flow rates (mL/min.) Temperature (C)

Nitrogen (make-up): 30 Injector: 250
Hydrogen (carrier): 1 Detector: 250
Hydrogen (detector): 2 Column: 250
Air: 30
Injection size: 1 L
Chromatogram: (See Figures 1)

3.5.2. Peak areas are measured by an integrator or other suitable means.

3.6. Interferences (analytical)

3.6.1. Any compound having the general retention time of the analyte is an interference. Possible interferences should be listed on the sample data sheet. GC parameters should be adjusted if necessary so these interferences will pose no problems.

3.6.2. Retention time data on a single column is not considered proof of chemical identity. Samples over the target concentration should be confirmed by GC/Mass Spec or other suitable means.

3.7. Calculations

3.7.1. A curve with area counts versus concentration is calculated from the calibration standards.

3.7.2. The area counts for the samples are plotted with the calibration curve to obtain the concentration of phenothiazine in solution.

3.7.3. To calculate the air concentration of phenothiazine (PT) the following equation is used:

mg/m3 = (PT g/mL)(3 mL)(mg)(1000 L)
(air volume in L)(1000 g)(m3)

where :

PT g/mL = amount of PT from curve
3mL = extraction volume
air volume = air volume of the sample

3.8. Safety precautions

3.8.1. All handling of solvents should be done in a hood.

3.8.2. Avoid skin contact with all solvents.

3.8.3. Wear safety glasses at all times.

4. Recommendations for further study

Collection studies should be performed. Analysis of phenothiazine can also be done by liquid chromatography according to literature.

A standard of 165 g/mL phenothiazine in methyl t-butyl ether

Figure 1. A standard of 165 g/mL phenothiazine in methyl t-butyl ether.

5. References

5.1. "Documentation of the Threshold Limit Values and Biological Exposure Indices", Fifth Edition, American Conference of Governmental Industrial Hygienists Inc., Cincinnati, OH, 1986, p. 472.

5.2. Windholz, M., "The Merck Index", Tenth Edition, Merck & Co., Rahway N.J., 1983, p. 1046.