The development of infrared spectroscopic methods for the analysis of air-borne asbestos

Our research purpose is to build up new and efficient methods to quantitate amounts of air-borne asbestos. A basic idea behind the methods is the use of a FT-IR instrument to measure the asbestos absorbances. Karen McCune, an ex-coworker in our group, developed three procedures to eliminate background absorbances from the filters on which the asbestos is collected. These procedures included the spectral subtraction, the chemical digestion, and the ashing of cellulose ester filters.My research has ultilized and expanded on the ashing procedure. First, the detection limits and linearity of the aforementioned transmission method were determined. Using amosite asbestos, we developed a standard curve from 40 tg to 2 µg which agreed well with Beer's Law. We determined that the detection limit of this method resulted from minutely contaminated salt and not from instrumental limitations. Even using highly pure KBr, CsCl, or KC1, similar detection limits were obtained.Second, the use of diffuse reflection to measure the asbestos absorbances was investigated. The method, much simpler than the transmission technique, consists of pouring the recovered asbestos-salt mixture into a small cup and obtaining the diffuse reflectance spectrum using a special accessory. A standard curve of amosite ranging from 40 p.g to 1 .tg was produced. One important observation was that when KCl adsorbed water from the air while a background spectrum was collected, the water absorption band contributed negatively to the area under the Si-O stretching region. This contribution prohibits the detection of smaller amounts of amosite. A standard curve of chrysotile asbestos ranging from 40 µg to 5 µg was also produced.Another goal of our research is to investigate the quantitation and identification capabilities when asbestos is present as mixtures of amosite, chrysotile, or other closely related silicates such as, kaolin. In conjunction with the diffuse reflection method, a curve fitting program was used to analyze the amount of each component in a mixture. First mixtures of amosite and chrysotile were studied. Then mixtures of amosite, chrysotile, and kaolin, mixtures which resemble the real world's environment, were studied.Overall, the FT-IR spectroscopic methods are more efficient and applicable than the traditional fiber-counting methods. Our methods not only objectively quantitate the amount of asbestos but also identify the type.Department of ChemistryThesis (M.S.