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The standard collection filter medium for particulate air pollutants has been fiberglass. The high metal impurity content of glass and the tedious acid extraction procedure necessary to recover metals from particulates are great disadvantages when trace analysis is to be performed. Samples on paper filters, on the other hand, can be dry ashed to 500°C without serious loss of metals by volatilization. The filter is completely destroyed leaving only inorganic residue to be dissolved for analysis by atomic absorption spectrometry.
Analysis of New York City particulates collected on paper filters indicate that results obtained by dry ashing compare favorably with those of accepted methods such as wet ashing and low temperature ashing. Reported losses of metals during dry ashing of particulates on fiberglass filters are not necessarily due to volatilization as has been commonly supposed. Metals such as lead, zinc, copper, and cadmium are retained to glass to varying extents at high temperature either by formation of insoluble metal silicates or by physical entrapment by softened glass.
sampling, filters, air pollution, atomic absorption spectrometry, trace elements
Analytical chemist, Bell Laboratories, Murray Hill, N.J.
Professor of chemistry, The Cooper Union for the Advancement of Science and Art, New York, N.Y.
Senior chemist, New York, N.Y.