Development of a method for determination of methylene chloride emissions at stationary sources.

Prior to source sampling, laboratory experiments were conducted to determine the best sample container in which to collect an integrated sample. It was found that CH/sub 2/Cl/sub 2/ remained stable in Tedlar bags for at least four weeks. The analytical method selected was gas chromatography with flame ionization detection (GC/FID). During the field portion of the study, both manufacturer and user emissions sources of CH/sub 2/Cl/sub 2/ were tested. Multiple sets of simultaneous quadruplicate bag samples were collected to determine the precision of both sampling and analysis in the field. All samples were analyzed at the test site after collection and then returned to Research Triangle Park. Samples were subsequently reanalyzed in the laboratories of Radian and the US EPA using three GC/FID instruments and two types of GC columns. The range of concentrations from the sources was 100 ppm to 27,000 ppm CH/sub 2/Cl/sub 2/. A statistical analysis of samples collected simultaneously showed no difference in the samples, proving good precision in both sampling and analysis. Some of the sample bags returned from the test sites developed leaks indicating that immediate on-site analysis is best. A comparison of results obtained in the field and the two laboratories showed thatmore » inter- and intra-laboratory precision was within 10%.« less