Nitrophenyl pentadienal, nitrophenylpentadienal, NPPD, or METKA (Russian for "mark") colloquially known as "spy dust",[1] is a chemical compound used as a tagging agent by the KGB during the Cold War Soviet Era. Soviet authorities in Moscow tracked Americans by applying an almost invisible powder to their clothing, cars, doorknobs and other objects. Some other variants of "spy dust" may have contained luminol and would glow under ultraviolet light.[2][3][4]
History
Spy dust was first discovered in England in the 1930s.[5]
In the summer of 1985 the powder began to appear in Moscow in much larger quantities. Concerned about the health effects of the substance, the United StatesState Department publicly protested to the Soviets. It was later determined that the health threat was low.[7][8][9]
Beginning about 2005-2015, a chemical tracking kit for law enforcement agencies was developed using NPPD.[10] To detect NPPD a 0.1% methanol solution of naphthoresorcinol is added to a swab of the item in question and then concentrated hydrochloric acid is added. The observation of a red color indicates a positive test.[11] Naphthoresorcinol was frequently used in early organic chemistry investigations to determine the presence of aldehyde groups in solution; a red adduct is formed in acidic solution.[12]
^Klopman G, Kalos A, Frierson M, Rosenkranz HS (1986). "NPPD (spy dust) is predicted to be a mutagen". Environ Mutagen. 8 (4): 627–30. doi:10.1002/em.2860080413. PMID3525138.