National Institute for Occupational Safety and Health

“ Consequently, live tuberculosis bacteria may be collected during air sampling. Inhalation of tuberculosis bacteria in aerosols is the only notable means of transmission which results in infection. Infection does not result from skin contact. Thus, the analyst is safe as long as aerosols are not produced. The use of alcohol to kill tuberculosis bacteria simply increases the degree of safety. ”

“ Calibrate daily with at least six working standards. a. Add known aliquots of sulfate calibration stock solution to eluent in 50-mL volumetric flasks and dilute to the mark to produce solutions containing 1 to 20 μg/mL SO 24-. b. Prepare sulfite standards in the same manner over the same range. c. Store working standards in tightly-capped polyethylene bottles. Prepare fresh working standards daily. d. Analyze working standards with samples and blanks (steps 8 through 10) . Prepare a calibration graph for each anion [peak height (mm or μS) vs. μg sulfite or sulfate] . ”

“ The component of the coefficient of variation of the method that arises from analytical variability, determined from the analysis of filters sampled at a dynamic test gas apparatus, was 0.8% to 1.3% for hydrogen chloride and 1.1% to 8.8% for nitric acid; and as determined from the analyses of spiked samples of hydrogen bromide, this value was 0.8% to 1.4% [3] . ”

“ Counts are to be recorded on a data sheet that provides, as a minimum, spaces on which to record the counts for each field, filter identification number, analyst’s name, date, total fibers counted, total fields counted, average count, fiber density, and commentary. Average count is calculated by dividing the total fiber count by the number of fields observed. Fiber density (fibers/mm2) is defined as the average count (fibers/field) divided by the field (graticule) area (mm2/field) . ”

“ Every compound-specific quantitative analytical technique, including FTIR spectrometry, can fail to provide accurate results when interfering compounds appear in a sample. However, the results of a mathematical FTIR spectral analysis designed for a particular set of compounds provides clues to its failure in the presence of interferants. An experienced analyst can often adjust the analysis to accommodate the interferants and provide accurate results. ”

“ All work should be performed with adequate ventilation for personnel and equipment. It is imperative that acid be added to water in order to avoid a violent exothermic reaction. There is risk of fire and explosion when phosphoric acid has contact with bases, combustible substances, oxidizing agents, reducing agents or water. Avoid physical contact since both sulfuric and phosphoric acid are both corrosive and irritants to eyes, skin, and the respiratory system. ”

“ Prepare stock solutions by adding known amounts of analytes to 10-mL volumetric flasks containing high purity solvent (carbon disulfide, methanol, toluene) . Solvents are chosen based on solubility for the analytes of interest and ability to be separated from the analytes when chromatographed. Highly volatile compounds should be dissolved in a less volatile solvent. For most compounds, carbon disulfide is a good general purpose solvent, although this will interfere with early eluting compounds. ”

“ Calculate and record the normalized intensity for the analyte peak on each sample and standard:
f.
For each media blank, determine the net count for the analyte diffraction peak. Calculate the average normalized intensity, Î b, for the 6 media blanks. Determine net count, I Ag, of an interference-free silver peak on the filter following the same procedure. Scan times should be shorter for the silver peak (e.g., about 5% of scan times for analyte peaks) and should be consistent throughout the method. For each media blank, determine the net count for the silver peak. ”

“ Desorption efficiency studies as performed by OSHA [1] using 6 samples at 3 levels gave a recovery of 99.0% for DETA, 99.2% for EDA, and 99.8% for TETA. The recovery of DETA, EDA, and TETA from samples used in a 15-day storage study was 89, 94, and 91%, respectively. These samples were generated by spiking the amines onto a glass wool plug in front of a sampling tube and drawing approximately 10 liters of air at 80% relative humidity through them. A 30-day storage study conducted by NIOSH [2] showed similar recoveries. ”

“ Dimethyl sulfate is a suspect carcinogen, and both the liquid and vapor are extremely severe irritants to skin, eyes, and mucous membranes. It is an insidious hazard -- warning properties are poor and symptoms are delayed up to 10 h or more [3,4] . All transfers involving dimethyl sulfate should be performed in a fume hood. Personal protective equipment should be used to prevent any bodily exposure even to the vapor. ”

“ It is not critical to know the exact volume of desorption solution and wetting alcohol used per sample. It only needs to be enough to cover the samples and to permit free percolation through the samples. See step 7. b.) If a set of samples consists predominantly of 2 gauze wipes, the QB, QC, and QD should also consist of 2 wipes and treated as per the samples. The volume of isopropanol (or methanol) added to the QC samples should be increased to 4 mL for two gauze wipes to simulate samples containing two gauze wipes. ”

“ The difference between the "found" and "true" concentrations may not represent a bias in the sampling and analytical method, but rather a random variation from the experimentally determined "true" concentration. Therefore, the method has no uncorrected bias. Storage stability studies on samples collected in a test atmosphere at a concentration of 5.80 mg/m 3 indicated that collected samples are stable for at least 7 days at 8 °C. Collection efficiency for the midget bubbler was determined to be 0.96 for an average of 24 samples and a correction must be applied. ”

“ Bias can also be caused in a cyclone by the pulsation of the personal sampling pump. Bartley, et al. [12] showed that cyclone samples with pulsating flow can have negative bias as large as −0.22 relative to samples with steady flow. The magnitude of the bias depends on the amplitude of the pulsation at the cyclone aperture and the dust size distribution. For pumps with instantaneous flow rates within 20% of the mean, the pulsation bias magnitude is less than 0.02 for most dust size distributions encountered in the workplace. Electric charges on the dust and the cyclone will also cause bias. ”

“ Analyze the sample filters by step-scanning the most intense interference-free diffraction peak of zinc oxide and determine the integrated intensity. Measure the background on each side of the peak for one half the time used for peak scanning and add the counts from each side for a total (average) background. Determine the 2-theta position of the background for each sample. The net count or intensity, I x, is the difference between the peak integrated count and the total background count. The net intensity is normalized as in step 12 to obtain . ”

“ Recoveries of CCV standards must meet guidelines of regulatory agency (80-120% is a reasonable target in the absence of specific guidance) . The CCV standards may be referred to in some guidance documents as ‘QC samples’ but such QCs are equivalent to liquid standards (not matrix spiked samples) and serve the same purpose of the CCVs in this method. NOTE 2: With the GC/MS it is possible to achieve the lower limit of 0.05 μg or less per sample for methamphetamine in either the scan mode or SIM mode. The scan mode is essential where the identification of unknowns is an analytical objective. ”

“ At the highest ETS concentration and a sampling rate of 1 L/min, over 3000 L of air would need to be sampled to reach the sampling tube capacity. Sampling rates and times typically employed in field studies would almost never exceed the capacity of the XAD-4 sampling tube. When sampling for nicotine in ETS, only the XAD-4sampling tube is employed. However, when sampling for nicotine where particulate matter is present, such as in the greenhouse study, it may be necessary to use a glass fiber filter (GFF) in series with the XAD-4 sorbent tube. ”

“ WIPE SAMPLING-This analytical method was used to analyze environmental samples collected on gauze pads and smear tabs. MDA was spiked onto acid-treated gauze pads, plain gauze pads, and smear tabs at 92, 9.2, and 0.92 μg per sample. Sets of each concentration were extracted immediately after allowing the spiking solution to evaporate, one day, one week, and one month after spiking. The extraction solution consisted of 10 mL 0.1 N methanolic KOH for the gauze pads and 2 mL for the smear tabs. The best recovery was obtained when the media were extracted immediately after the methanol evaporated. ”