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This paper presents specific examples of problem solving involving the complex matrix. The purpose is to encourage development and comparison of methods with the goal of creating systematic analytical protocols for many waste types.
Complex matrix chemistry is becoming more important in environmental analysis. Many waste matrices are unique to an industrial process and common worldwide. Only recently has analysis of many complex wastes been attempted, primarily because of environmental concerns and regulations. The complex matrix can be multiphase, chemically unstable, and contain analytical interferences. Complicating factors include waste aging and total versus releasable constituents.
Multiphase wastes can contain organic compounds, water, and solids. Examples of centrifugation and extraction of sludges are shown to simplify analysis. The extracts are more uniform and can be analyzed separately with more reproducible results. However, careful attention must be paid to mass, volume, and specific gravity of the separated fractions to be able to reconstruct the original samples. Anaerobic bacteria in petroleum refinery sludges can rapidly generate sulfide in a sample and lead to misleading conclusions about the real hazard of the waste.
Analysis for sulfide immediately after sampling is recommended. Other changes in chemically active wastes, including oxidation, often occur naturally in the disposal environment. These changes caused by aging are shown to confound analytical results and make interpretation of environmental impact difficult.
Matrix interferences in sulfur analyses can be overcome with appropriate analytical techniques. Matrix effects are explained, and comparisons of X-ray fluorescence and combustion are made. The sulfur result is also shown to present a problem in heat content calculation. The success of total assay of metals is dependent on specimen preparation. A comparison of three methods is given and a recommendation made. New test methods under development by ASTM for environmental modeling are presented as future options. The use of background information is recommended to optimize analytical techniques and provide the most useful data.
industrial wastes, oily wastes, waste preparation, complex waste matrix, oil, inductively coupled plasma spectroscopy (ICP), EPA tests, method comparison, hazard assessment, quality assurance, Resource Conservation and Recovery Act, data interpretation
Environmental chemist, Standard Oil Research Center, Cleveland, OH