Abstract: A testing assembly for the rapid detection of a desired chemical from a sample, the testing assembly having a sample collection device for obtaining the sample and depositing the sample into a chemical capture cartridge that operably engages with a sensing device, the chemical capture cartridge utilizing the microdiffusion of reagents to isolate the desired chemical from the sample and react the desired chemical to form a detectible complex that can be detected and measured. The testing assembly can be portable and can rapidly diagnose a toxic industrial chemical exposure in just a few minutes, preferably about a minute or less for cyanide exposure using a blood sample from a subject onsite. The testing assembly can be used to determine the presence and/or concentration of a toxic industrial chemical in a variety of samples, including biological, environmental, and industrial samples.