Zwikker reaction
The Zwikker reaction is an identity check for barbiturates that are not substituted on nitrogen . In this process, derivatives of barbituric acid are reacted with cobalt (II) or copper (II) salts in an alkaline environment, creating colored complexes . It bears the name of its discoverer Jan Jacobus Lijnst Zwikker .
To detect barbiturate, the sample to be examined is mixed with the Zwikker reagent , consisting of an aqueous copper (II) sulphate solution mixed with pyridine . In the presence of barbiturates, a pinkish-purple precipitate forms after a while, thiobarbiturates result in a green precipitate. In the complexes formed , the barbiturate coordinates as a bidentate chelate ligand via nitrogen and oxygen at the metal center.
The Zwikker reaction, however, only allows group detection; it is not possible to differentiate between individual barbiturates. Furthermore, other substances also provide positive evidence. These include, for example, theophylline , hydantoin derivatives, sodium salicylate and aureomycin .
Individual evidence
- ↑ a b c G. Schmidt: About the specificity of the Zwikker reaction in barbiturate detection , in: International Journal of Legal Medicine 1961 , 51 , 534-536; doi : 10.1007 / BF00575892 .
- ^ A b W. Hansel, S. Umlauff: Barbiturate analysis with heavy metal ions from the beginnings to the present , in: Pharmazie in our time 1993 , 22 , 207-213; doi : 10.1002 / pauz.19930220423 .
- ↑ Pharmac. Weekbl. 68 (1931), pp. 975 ff. Retrieved January 13, 2019 .