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These procedures were designed and tested for internal use by OSHA personnel. Mention of any company name or commercial product does not constitute endorsement by OSHA.
|Target concentration:||10 ppm (OSHA PEL)|
|Procedure:||Samples are collected on Chromosorb 106 tubes, desorbed with carbon disulfide and analyzed by gas chromatography with a flame ionization detector (FID).|
|Recommended air volume
and sampling rate:
10 L at 0.2 L/min
|Reliable quantitation limit:||0.08 ppm (0.4 mg/m3)|
|Standard error of estimate
at the target concentration:
|Status of method:||Evaluated method. This method has been subjected to the established evaluation procedures of the Organic Methods Evaluation Branch.|
|Date: April 1982||
Chemist: Mary Eide
Organic Methods Evaluation Branch
OSHA Salt Lake Technical Center
Salt Lake City, UT 84165-0200
NIOSH method S292 recommends collection of naphthalene on charcoal tubes and desorption with carbon disulfide (Ref. 5.1.). Naphthalene desorption efficiency in this method (S292) is dependent upon the mass of naphthalene on the charcoal tube. NIOSH requires a 75% or better desorption efficiency for its methods. A loading of 10 mg of naphthalene on the charcoal tube gives a 76.2% desorption efficiency. To obtain a loading of 10 mg of naphthalene from an atmosphere at the PEL of 10 ppm, 200 L of air must be sampled. This is the air volume recommended by NIOSH. With lower loading the desorption efficiency decreases, for example at 0.5 mg, equivalent to the PEL of 10 ppm with a 10-L air volume, the desorption efficiency is 61%.
Other solvents were considered for desorbing charcoal tubes, but no solvent better than carbon disulfide was found. Other collection tubes tried were XAD-4, Coated Resin (SKC, cat. no. 226-23), and Chromosorb 106. Chromosorb 106 had a 100% desorption efficiency over the range of 0.004 mg to 1.02 mg loading, when desorbed with carbon disulfide, and samples were stable over a 17-day storage time.
Naphthalene is readily absorbed through the skin and can cause skin irritation, corneal ulcerations, and cataracts (Refs. 5.2. and 5.3.). Naphthalene inhalation and ingestion can cause headaches, nausea, extensive sweating, and confusion. Symptoms of severe poisoning are vomiting, then coma, and hematuria (Ref. 5.4.). Sensitive individuals can have a "hemolytic crisis" (rupture of red blood cells) when exposed to naphthalene (Ref. 5.5.). Naphthalene has been shown to be a teratogen in rats (Ref. 5.6.).
The major uses of naphthalene in 1978 were: phthalic anhydride production (141,000 metric tons), insecticide production (35,000 metric tons), 2-naphthol production (16,000 metric tons), synthetic tanning agents (12,000 metric tons), moth repellents (4,000 metric tons), surfactant production (2,000 metric tons), and miscellaneous (2,000 metric tons) (Ref. 5.7.). The total consumption in 1979 was 212,000 metric tons, while the production in 1979 was 226,000 metric tons. The major sources of naphthalene are from coal tars and petroleum refineries (Ref. 5.7.).
|vapor pressure:||0.05 mm Hg at 20°C|
|flash point:||79°C (174°F) (closed cup)|
|lower explosive limit:||0.9%|
|odor threshold:||0.3 ppm|
|structural formula:||Figure 1.1.4.|
The detection limit of the analytical procedure is 4 ng per injection. This is the amount of analyte that gives a peak area similar to the peak area of trace contaminants in the desorbing solution. (Section 4.1.)
The detection limit of the overall procedure is 4 µg per sample (0.08 ppm or 0.4 mg/m3, assuming the recommended air volume). This is the amount of analyte spiked on the sampling tube which allows recovery of an amount of analyte equivalent to the detection limit of the analytical procedure. (Section 4.2.)
The reliable quantitation limit is 4 µg per sample (0.08 ppm or 0.4 mg/m3, assuming the recommended air volume). This is the smallest amount of analyte which can be quantitated within the criteria of 75% recovery and 95% confidence limits of ±25%. (Section 4.3.)
The sensitivity of the analytical procedure over a concentration range representing 0.5 to 2 times the target concentration based on the recommended air volume is 684 area units per µg/mL. This is determined by the slope of the calibration curve. (Section 4.4.) The sensitivity may vary with the particular instrument used in the analysis. The instrument used in this evaluation was a Hewlett-Packard 5840A.
The recovery of analyte from the collection medium during storage must be 75% or greater. The recovery of naphthalene from samples used in a 17-day storage test remained above 94% when the samples were stored at both 23°C and -5°C. (Section 4.6.)
The pooled coefficient of variation obtained from replicate determinations of analytical standards at 0.5, 1, and 2 times the target concentration is 0.0058. (Section 4.4.)
The precision at the 95% confidence level for the 17-day storage test is ±12.5%. (Figure 4.6.2.) This includes an additional ±5% for sampling error.
The desorption efficiency was essentially 100% for 0.5 to 2 times the PEL for a 10-L air sample (Section 4.5. and 4.2.).
Suspected interferences should be listed on sample data sheets.
|flow rates (mL/min)||temperature (°C)|
|injection size:||1 µL|
|elution time:||4.62 min|
ppm = (1 mL)(A)(24.46)/(128.2)(10 L)
where A = µg/mL of naphthalene in standard
128.2 = molecular weight of naphthalene
1 mL = desorption volume
24.46 = molar volume (L/mole) at 25°C and 760 mm Hg
ppm naphthalene = (A-C)/(B)(0.1)
where A = ppm calculated by integrator
B = air volume (L)
C = blank amount (ppm)
The detection limit of the analytical procedure was determined by injecting 1 µL of a 4.0 µg/mL standard prepared in carbon disulfide containing 1 µL/mL n-hexylbenzene internal standard. The detection limit of the analytical procedure is 4 ng per injection. Chromatograms of such a determination are shown in Figure 4.1.
The detection limit of the overall procedure was determined from the following desorption data. This data is presented graphically in Figures 4.2.1. and 4.2.2.
Detection Limit Data
The recovery of naphthalene from three samples spiked with an amount equivalent to the detection limit of the overall procedure, was 103.6%, 102.03% and 99.25%. The average of these values is 101.7% and the standard deviation is 2.20%. Therefore, the 95% confidence limits (±1.96 SD) is ±4.32%.
Four analytical standards whose concentrations are indicated below were each analyzed six times. The data listed in Table 4.4 were used to determine the calibration curve shown in Figure 4.4. The precision of the analytical method was determined with the 0.5×, 0.9×, and 2× data.
Sensitivity and Precision
|× target conc.
CV = 0.0058
Desorption efficiencies were determined by injecting a solution of naphthalene in o-xylene onto Chromosorb 106 tubes and analyzing them a day later. The desorption efficiencies were determined with sample loadings equivalent to 0.5, 1, and 2 times the target concentration based on the recommended air volume of 10 L. Six samples were prepared and analyzed at each concentration.
|× target conc.||0.5×||1×||2×|
X = 101.8
Storage samples were prepared by vapor spiking Chromosorb 106 tubes with naphthalene. Tubes containing silanized glass wool were liquid spiked with 5.0 µL of 100.12 mg/mL naphthalene in o-xylene. These tubes were placed in series ahead of Chromosorb 106 tubes and humid air was drawn through them. The naphthalene was leached from the glass wool and adsorbed on the Chromosorb 106. Six samples were analyzed the day after generation. They had been stored in a refrigerator at -5°C. Fifteen samples were stored at -5°C and 15 samples were stored at room temperature (23°C). Three samples from each set were analyzed at intervals of a few days over a 17-day period. Results are shown graphically in Figures 4.6.1. and 4.6.2.
| % recovery
| % recovery
A Teflon gas bag was filled with 60 L of humid air at 80% relative humidity. A solution containing 24 mg of naphthalene in xylene was injected into the gas bag. The gas bag was allowed to equilibrate for 25 h. Naphthalene crystals were observed in the gas bag after this period of time. Samples were taken from the gas bag using a Chromosorb 106 tube containing only the 100-mg section of adsorbent connected in series with a normal Chromosorb 106 tube. The flow was from the gas bag, through the tube with the main section only, then through the second Chromosorb 106 tube. This second Chromosorb 106 tube was changed at timed intervals and analyzed for the presence of naphthalene. The air was drawn at 0.192 L/min.
Breakthrough Study Using a Gas Bag
total air drawn
Breakthrough Study Using Spiked Glass Wool
|total air drawn
glass wool tube
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