PARAFFIN WAX FUMES
SOLVENTS BRANCH 1. General Discussion
The OSHA Laboratory recently received samples collected on glass fiber filters requesting paraffin wax fume analysis. Although this collection method has been recommended for many years, the supporting documentation had not been collected. Since there is a TLV and samples were received, it was decided to perform the laboratory work needed to evaluate this sampling and analytical procedure. 1.1.2. Toxicity Pure paraffin wax is widely regarded as non toxic, but may possess some carcinogenic properties.(Ref 5.3) These properties are largely believed to be due to polycyclic aromatic hydrocarbons, but most processed waxes in use in America today do not possess any measurable levels of polycyclics. (Ref 5.1) Work around molten paraffin, especially if it is overheated is more uncomfortable and nauseating than dangerous. (Ref 5.4) 1.1.2. Potential workplace exposure Workers are exposed to paraffin wax fumes in a variety of industries. Any time that paraffin solid is heated a fume may be produced. Paraffin is ideal for use as a sealer or waterproofing agent. Coating of paper for use as containers for milk is one of the largest uses of paraffin. (Ref 5.1) It is also used in the candle making industry and as an original mold in the casting industry. 1.1.3. Physical properties:
1.2. Limit defining parameters
1.2.2. The overall detection limit is 0.034 mg/m3 based on a 100 liter air volume and a 2 mL desorption volume. Air concentrations given throughout this procedure are based on a 100 liter air volume and 2 mL desorption volume. 1.3. Advantages
1.3.2. The analytical method is reproducible and sensitive. 1.3.3. Reanalysis of samples is possible. 1.4. Disadvantages
2. Sampling procedure
2.1.2. A three piece plastic sampling cassette capable of holding a 37 mm glass fiber filter. 2.2. Sampling technique
2.2.2. Connect the sampling 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 sampling cassette.
2.2.4. Replace the inlet half of the cassette. Seal the cassette with
plastic plugs immediately after sampling. Seal each sample covering the
plugs with OSHA 2.2.6. With each batch of samples, submit at least one blank. This cassette should be subjected to exactly the same handling as the samples, except no air is drawn through it. 2.2.7. Send the samples and corresponding paperwork to the lab for analysis. 2.2.8. Bulks submitted for analysis must be shipped in a separate container from the air samples. 2.3. Extraction efficiency
Extraction Efficiency
2.4. Retention efficiency
Retention Study
2.5. Storage
Storage Study
2.6. Air volume and sampling rate studied
2.6.2. The sampling rate studied is 1 liter per minute. 2.7. Interferences Suspected interferences should be listed on sample data sheets. 2.8. Safety precautions
2.8.2. Safety glasses should be worn at all times. 2.8.3. Follow all safety practices that apply to the workplace being sampled. 3. Analytical method
3.1.2. GC column capable of separating the analyte and an internal standard, if used, from any interferences. The column used in this study was a DB-1 fused silica capillary having the following dimensions; 6 meter length, 0.32 mm ID, 1 u film. 3.1.3. An electronic integrator or some other suitable method of measuring peak areas. 3.1.4. Two milliliter vials with Teflon lined caps. 3.1.5. A 10 uL syringe or other convenient size for sample injection. 3.1.6. Pipettes for dispensing the desorbing solution. The Glenco 1 mL dispenser was used in this method. 3.1.7. Volumetric flasks - 10 mL and other convenient sizes for preparing standards. 3.2. Reagents
3.2.2. Carbon disulfide, Reagent grade. 3.3.3. Parowax paraffin used as the analytical standard. 3.3. Sample preparation
3.3.2. Each filter is extracted with 2 mL carbon disulfide. 3.3.3. The vials are sealed immediately and extracted for 30 minutes with occasional shaking. 3.4. Standard preparation
3.4.2. A range of separate standards should be made so that the sample results are bracketed. 3.5. Analysis
3.5.2. Peak areas are measured by an integrator or other suitable means. 3.5.3. Precision was measured by by making 6 consecutive injections of 4 different standards containing Parowax concentrations of 37, 200, 372, and 751 ug/mL. The pooled coefficient of variation is 0.016. (Table 4)
Precision
A(1), A(2),A(3),A(4) = # of injections at each level 3.6. Interferences (analytical)
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
3.8. Safety precautions
3.8.2. Avoid skin contact with all solvents. 3.8.3. Wear safety glasses at all times. 4. Recommendations for further study The method seems adequate for both collection and analysis. The only thing that is left to look at is actual quantitative collection of fumes. Paraffin fumes have been produced by heating Parowax in a bubbler tube and collecting them on a filter attached to the exit port. The collection appeared to be good with no breakthrough to the backup pad. But no quantitative check has been performed using an actual dynamic atmosphere of paraffin fumes.
Much of the analytical work could possibly be avoided by the use of
pre- and post-weighings. It is unusual to have other contaminates in
areas where paraffin wax fumes are being emitted. By using weighings
to determine the total mass present on the filter it may be possible to
eliminate the chromatographic determination of samples with little or no
contamination. Most samples received at the lababoratory fall into this
category. This is an area that may warrant further study.
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5. References 1) P. Shubik et al; "Studies on the Toxicity of Petroleum Waxes"; Toxicology and Applied Pharmacology; Aug. 2 1962. 2) "Encyclopedia of Chemical Toxicology", vol #24, Third Edition, Kirk-Othmer. 3) R. Prosser White "The Dermatergoses or Occupational Affections of the Skin" London H.K. Lewis & Co. 1934.
4) "Queries and Minor Notes" Journal of American Medical Assoc. 110:2102 1938.
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