In some embodiments, the present disclosure pertains to substance detecting assemblies that include: (1) a sample medium (e.g., filter paper); and (2) a solid test chemical (e.g., zinc) impregnated with the sample medium. In some embodiments, the present disclosure pertains to methods of making an assembly for detecting a substance by: (1) providing a sample medium; (2) providing a solid test chemical; and (3) impregnating the sample medium with the solid test chemical. In further embodiments, the present disclosure pertains to methods for detecting a substance by: (1) collecting the substance on a sample medium that is impregnated with a solid test chemical; and (2) initiating a reaction of the substance with the solid test chemical on the sample medium to generate a color that corresponds to the substance. In some embodiments, the sample medium is then inserted into a chemical detection unit for the detection of the substance.