A porous thin film and a method are disclosed. The film has a generally uniform thickness and includes fused silica particles that provide multiple types of pores in the film. Particles are generally uniformly distributed on a surface and have a generally open structure that provides the film with an open interface readily accessible to fluids. The film provides for preconcentration of, e.g., heavy metals in fluid and gas samples that provides for direct determination of the analytes.
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