NORA Manufacturing Sector Strategic Goals
927ZJGCa - Interferent Effects on Organic Vapor Monitor PerformanceStart Date: 10/1/2009
End Date: 9/30/2012
Principal Investigator (PI)Name: Christopher Coffey
Funded By: NIOSH
Primary Goal Addressed5.0
Secondary Goal Addressed
Attributed to Manufacturing
The study will investigate the effects of interferents and environmental conditions on the performance of DROVMs using cyclohexane, (vapor of interest), hexane, 2-butanone, trichloroethylene, and toluene (interferents). The test temperatures will be 5°C, 21°C, and 38°C and the four relative humidities will be 15, 30%, 60%, and 90%). Three SapphIRes and TVAs will be evaluated. Four vapor concentrations will be tested 12, 144, 289, and 450 ppm in various ratios of cyclohexane:interferent. There will be five replicates at each test. Each test will last 30 minutes. The DVORM results will be compared to charcoal tubes analyzed using NIOSH Method 1500 and canister samples that will be analyzed in-house by a gas chromatography-mass selective detector system using pairwise comparison and the intersection-union test for establishing equivalency of sampling devices.
This study will evaluate three MIRAN SapphIRe Portable Ambient Air Analyzers and Century Portable Toxic Vapor Analyzers (TVA) in the following three phases:
Phase 1: Calibration using the vapor of interest
The purpose of this phase is to compare the performance of the DVROMs to NIOSH Method 1500 and an evacuated canister method when calibrated per the manufacturers' instructions vs. calibration with the gas/vapor of interest. The instruments will be calibrated per the manufacturer's instructions. For the second series of tests, both instrument groups will be calibrated using four concentrations of cyclohexane (i.e., the vapor of interest). Each series of tests will be conducted at different temperatures and RHs to determine their effect on the DROVM performance. The three temperatures will be 5, 21, and 38°C and the four relative humidities will be 15, 30%, 60%, and 90%. Four concentrations of cyclohexane will be used. Charcoal sorbent sample tubes will be used and analyzed in accordance with NIOSH Method and two 400 cc evacuated silonite-coated stainless steel canisters equipped with a Passive Canister as standards to compare the DROVM performance.
Phase 2: Use temperature and humidity vs. room temperature and humidity calibration
The purpose of this phase is to compare the performance of the DROVMs to NIOSH Method 1500 and an evacuated canister method when calibrated at approximately normal office/laboratory environmental conditions (21°C and 50% RH) vs. the environmental conditions expected at the sampling site. This phase will consist of two series of tests. For the first series of tests, the instruments will be calibrated per the manufacturer's instructions at 21°C and 50% RH. For the second set of tests, the instruments will be calibrated at the combination of temperature and humidity at which the instruments' performance was most different from the charcoal tubes and evacuated canisters. Both instrument types will be calibrated per the manufacturer's instructions. After each type of calibration, tests will be conducted at the combination of temperature and humidity at which the instruments' performance was most different from the charcoal tubes and evacuated canisters. Four concentrations of cyclohexane will be utilized. Charcoal sorbent sample tubes will be used and analyzed in accordance with NIOSH Method and two 400 cc evacuated silonite-coated stainless steel canisters equipped with a Passive Canister as standards to compare the DROVM performance. Each condition will be run five times.
Phase 3: Comparison of Performance of DROVMs using Interferents
In this phase the performance of the SapphIRes and TVAs will determined when sampling cyclohexane with and without interferents. Simulants for the interferents will be used: hexane, 2-butanone, trichloroethylene, and toluene. These contaminants are common chemicals which may be encountered during emergency response and represent different classes of organic compounds (straight-chain hydrocarbons, ketones, chlorinated hydrocarbons, and aromatics) which may elicit different instrument responses. In this phase, the instruments will be tested in the following combination of vapors: cyclohexane and hexane, cyclohexane and 2-butanone, cyclohexane and trichloroethylene, cyclohexane and toluene, and cyclohexane, hexane, 2-butanone, trichloroethylene, and toluene. Four concentrations of cyclohexane will be used (0, 30, 150, 300, and 475 ppm). Each of the four vapor concentrations will have multiple proportions of cyclohexane: interferents. The ratios will be 33%:67%, 50%:50%, and 67%:33% equaling each of the four concentrations. This will enable the determination of the effect of the interferents on DROVM performance. The instruments will be calibrated using the procedure determined to provide the closest DROVM performance to the charcoal tubes and evacuated canisters in phase 1. The temperature and RH to be used in this phase will be the combination from phase 2 that affects DROVM to the greatest degree. Each condition will be run five times. The DROVM performance determined in this phase will be compared to the DROVM performance for cyclohexane only as determined in the previous phases. The DROVM performance in phases 1 through 3 will be determined using the following methods:
1. The DROVM results for each test will be compared to average charcoal tube using pairwise comparisons. A DROVM average will be considered to be equivalent if it is within ±25% of the average charcoal tube concentration. Comparisons will be made across combined experimental conditions and across separated conditions, by target temperature, humidity, and concentration.
2. Comparison of the mean recorded levels by vapor type or concentration will utilize one-way ANOVA, with the main effect level being “vapor concentrations.”
The intersection-union test described by Krishnamoorthy and Mathew will also be used to evaluate comparability of the DROVMs to the charcoal tubes and canisters. This method is both a parametric and nonparametric test for establishing the equivalency of a sampling device to the standard.
The major objectives of the project are to determine if (1) the mean response of the direct-reading organic vapor monitors for sampling a vapor of interest alone equals the mean response of the direct reading organic vapor monitor for sampling the vapor of interest in a mixture of vapors; (2) the mean response of the direct-reading monitor when calibrated according the manufacturer's instructions equals the mean response of the monitor when calibrated with different vapors and at different calibration intervals differing from the manufacturer's instructions.
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