The present invention provides methods for determining the presence of oxidizing salts. According to the current invention, analyte is collected on a swipe and subsequently heated to a temperature sufficient to release a detectible vapor phase component of the oxidizing salt. The vapor phase component passes reacts with a pH sensitive molecule. Reaction of the vapor phase product with the pH sensitive molecule produces a detectible change in response intensity.

A sensing device that includes (a) an image sensor matrix that comprises a first pixel and a second pixel; wherein the first pixel is configured to generate a first detection signal indicative of a presence of a first analyte; wherein the second pixel is configured to generate a second detection signal that is indifferent to the presence of the first analyte; and (b) a processing circuit that is configured to determine the presence of the first analyte based on at least a relationship between the first detection signal and the second detection signal.

An analytical process for detecting compounds in a sample suspected of containing a peroxide-based compound, a nitrate-based compound, a nitrotoluene-based compound, or a nitramine-based compound includes treating the sample with a superbase and then contacting the sample with a composition. The composition includes or consists of a Ni-porphyrin and an acid and optionally an acid stable solvent.

An analytical process, which preferably is a one-step process, for detecting in a sample peroxide-based explosives, and/or nitrate-based explosives, the process comprising contacting a sample suspected of containing a peroxide-based compound, especially a peroxide-based explosive, or a nitrate salt, especially a nitrate-based explosive, with a composition comprising a Ni-porphyrin, an acid and preferably an acid-stable solvent.