Interlaboratory study of a test method measuring total volatile organic compound content of consumer products.

Consumer products are potentially significant sources of volatile organic compounds (VOCs), which are precursors to the formation of ozone in photochemical smog. To address the problem of ozone formation in ambient air, the U.S. Environmental Protection Agency (EPA) has been involved in the development of test methods for measuring the VOC content of consumer products. This paper describes results of an interlaboratory study to estimate the repeatability (precision of analyses performed by a single laboratory) and reproducibility (precision of analyses performed by different laboratories) of the consumer products' VOC measurement method based on EPA Method 24 (for VOCs in surface coatings). The mean method repeatability was 2.7 wt% VOC, and the mean method reproducibility was 4.8 wt% VOC. Method repeatability ranged from 0.2 to 4.4 wt% VOC, and reproducibility ranged from 0.6 to 11.9 weight percent VOC. The precision of the VOC method for consumer products is similar to the precision of EPA Method 24 for surface coatings.

Validation of a Test Method for Collection and Analysis of Chloroform Emissions From Stationary Sources.

A test method based upon the adsorption of chloroform onto charcoal was evaluated for the collection and analysis of chloroform emissions from stationary sources. In this method, a source gas sample is pulled through adsorption tubes containing activated charcoal (to adsorb the chloroform), and chloroform is extracted from the charcoal with a hexane/methanol mixture. The extract is analyzed by gas chromatography with an electron capture detector. Procedures in Environmental Protection Agency (EPA) Method 301 were utilized to test the suitability of the method under field conditions at two sampling sites (paper mills). EPA Method 301 requires that four separate trains ("quad train") operate simultaneously in each run. During each run, two of the four sampling trains were spiked with a known amount of gaseous chloroform. The quad train sampling was performed six or more times. In the first field test, the stack emissions of chloroform were approximately 300 ppm, the mean spike recovery was 82%, the precision of the method for unspiked samples was within 5%, and the sampling bias was -43 ppm. Modifications were made to the sampling method and the spike gas introduction system. The revised method was then tested at a second field site which had chloroform emissions of approximately 220 ppm. The mean spike recovery improved to 95%, the unspiked sample precision was within 5%, and the sampling bias improved to -8.5 ppm.

Validation of a test method for the measurement of methanol emissions from stationary sources.

Title III of the 1990 Clean Air Act Amendments designated methanol as a pollutant to be regulated. The U.S. Environmental Protection Agency (EPA), through a contract with Research Triangle Institute, has developed a method for measuring methanol emissions from stationary sources. The methanol sampling train (MST) consists of a glass-lined heated probe, two condensate knockout traps, and three sorbent cartridges packed with Anasorb 747. Samples are desorbed with a 1:1 mixture of carbon disulfide (CS2) and N,N-dimethylformamide (DMF). Condensate water and CS2/ DMF samples are analyzed by gas chromatography with flame ionization detection. The MST has a practical quantitation limit of approximately 3 ppm for a 20-L sample. Samples were shown to be stable for at least two weeks after collection. Field tests of the MST and the National Council of the Paper Industry for Air and Stream Improvement (NCASI) methanol sampling method were conducted at two pulp and paper mills. Sampling and analysis procedures followed EPA Method 301 requirements. The sampling location for the first field test was the inlet vent to a softwood bleach plant scrubber, where the methanol concentration was approximately 30 ppm. The mean recovery of spike was 108.3% for the MST method and 81.6% for the NCASI method. Although neither method showed significant bias at the 95% confidence level, the between-methods bias was significantly different. A second field test was conducted at a vent from a black liquor oxidation tank where the methanol concentration was approximately 350 ppm. Mean spike recoveries were 96.6 and 94.2% for the MST and NCASI methods, respectively. The biases of the two methods and the between-methods bias were not significantly different for the second field test.