Chiral on-chip separations of neurotransmitters.

The fast on-chip determination of a range of compounds of relevance in the study and treatment of neurological disorders is demonstrated. These include dopamine and its metabolites methoxytyramine, homovanillic acid, noradrenaline, adrenaline, normetanephrine, and metanephrine, its artificial precursors DOPA and tyrosine; and the related compounds DOPS and CDOPA. Two runs are needed for the determination of these compounds. The enantiomers of adrenaline, noradrenaline, and dopamine can be separated in a buffer containing the novel combination of a cyclodextrin and a dendrimer. The isomers of homovanillic acid, DOPA, CDOPA, methoxytyramine, metanephrine, and normetanephrine, which were found to interact more weakly with cyclodextrins, could be separated in approximately 3 min with a buffer containing a cyclodextrin and a crown ether. To our knowledge, this is the first report of a fast chiral separation of such a complex mixture on an electrophoresis chip. Detection was carried out amperometrically; derivatization of the analytes is not necessary.